Age-matched Sprague-Dawley Rats Research Articles

#2810 Exploring non-renal vasculature: therapeutic implications of proton pump inhibitor and anthelmintic treatment in PCK rat model

Abstract Background and Aims Cystic kidney diseases represent ciliopathies that can cause vascular damage through renal hypertension. Additionally, there is growing experimental evidence of endothelial cell abnormalities associated with ciliary protein deficiencies. PCK rats, a strain derived from Sprague-Dawley (SD) rats that develops both polycystic kidney disease (PKD) and liver disease, serve as a model for recessive PKD. The PCK rat model also presents abnormalities in non-renal vascular function. Another study from our group suggests a potential therapeutic benefit of repurposed therapy with a proton pump inhibitor (PPi) and an anthelmintic agent in attenuating the progression of PKD in a PCK rat model. Here, we investigated whether these drugs can also improve endothelial function. Method The compounds were administered to 3-week-old male and female PCK rats (n = 5-6) for a total of 10 weeks. Untreated PCK rats and age-matched SD rats (n = 5-6) served as controls. After perfusion fixation, the aorta was harvested and its thoracic rings were used to evaluate the contraction/relaxation responses ex vivo by organ bath experiments. Additional rings were preserved for histological and molecular biological analyses. Results Male PCK rats exhibited impaired endothelial function compared to healthy controls. Endothelium-dependent relaxation to acetylcholine was improved by 10% after treatment with PPi, while the anthelmintic administration had no protective effect. PKD also impaired endothelial function in female PCK rats compared to healthy SD controls. There was an improvement in endothelium-dependent relaxation to acetylcholine after treatment with PPi by 5.5%, while administration of the anthelmintic agent further impaired endothelial function. Conclusion 13-week-old PCK rats show endothelial dysfunction in non-renal vasculature. Treatment with a proton pump inhibitor improved endothelial function in male PCK rats to the level of healthy SD controls. By contrast, in a parallel study, the anthelmintic had a positive effect on renal function but a detrimental impact on endothelial function. These intricate relationships underscore the need for further exploration to understand the underlying mechanisms and broader implications of our findings, illustrating the challenges and potential avenues for the development of effective treatments for PKD.

YQBS Improves Cognitive Dysfunction in Diabetic Rats: Possible Association with Tyrosine and Tryptophan Metabolism.

This study is aimed to determine the metabolomic effects of the hybrid medicine formula Yi-Qi-Bu-Shen (YQBS) on the neurotransmitter aspects of cognitive impairment in diabetic rats. In the current study, streptozotocin (STZ) was used to induce diabetic animal model in male Sprague Dawley (SD) rats. After successful establishment of diabetic SD rats' model, age-matched healthy SD rats and diabetic SD rats were treated with low and high doses of YQBS, and then tested for learning memory ability and analyzed for pathological changes. In addition, neurotransmitter metabolic changes in hippocampal subdivisions of rats from different treated groups were analyzed using liquid chromatography-mass spectrometry (LC-MS) technique. YQBS could significantly improve memory-cognitive impairment in diabetic rats as evidenced by the shortening of latency to target and the reduction of latency first entrance to target. Moreover, YQBS also improved the pathological alterations in the hippocampal region in the brains of diabetic rats. Metabolomic analysis showed that the expression of noradrenaline hydrochloride was down-regulated and the expressions of levodopa and 5-hydroxytryptophan were up-regulated in the hippocampal tissues of diabetic rats treated with YQBS. These findings demonstrate that YQBS has protective effects against diabetic cognitive dysfunction, which might act through alteration in tyrosine and tryptophan metabolism.

Increased plasma drug concentration and decreased additional insulin secretion following oral administration of glimepiride in Spontaneously Diabetic Torii rats.

We aimed to evaluate the pharmacokinetics and pharmacological effects of glimepiride in the Spontaneously Diabetic Torii (SDT) rat, which is a non-obese model of type 2 diabetes. After oral administration of glimepiride (10 mg/kg), the maximum plasma concentrations and the area under the curve from 0 to 6 h of glimepiride in SDT rats were significantly higher than those in age-matched Sprague-Dawley rats. Whereas, additional insulin secretion following glimepiride treatment was markedly reduced in SDT rats. Thus, the SDT rat can be regarded as a model that reflects type 2 diabetes with reduced insulin secretory capacity. Our findings suggested that glimepiride could be ineffective in sever type 2 diabetic patients.

Effects of Δ⁹-tetrahydrocannabinol (THC) vapor inhalation in Sprague-Dawley and Wistar rats.

An inhalation system based on e-cigarette technology produces hypothermic and antinociceptive effects of Δ⁹-tetrahydrocannabinol (THC) in rats. Indirect comparison of some prior investigations suggested differential impact of inhaled THC between Wistar (WI) and Sprague-Dawley (SD) rats; thus, this study was conducted to directly compare the strains across inhaled and injected routes of administration. Groups (N = 8 per strain) of age-matched male SD and WI rats were prepared with radiotelemetry devices to measure temperature and then exposed to vapor from the propylene glycol (PG) vehicle or THC (25-200 mg/mL of PG) for 30 or 40 min. Additional studies evaluated effects of THC inhalation on plasma THC (50-200 mg/mL) and nociception (100-200 mg/mL) as well as the thermoregulatory effect of intraperitoneal injection of THC (5-30 mg/kg). Hypothermic effects of THC were more pronounced in SD rats, where plasma levels of THC were identical across strains, under either fixed inhalation conditions or injection of a mg/kg equivalent dose. Strain differences in hypothermia were largest after i.p. injection of THC, with SD rats exhibiting dose-dependent temperature reduction after 5 or 10 mg/kg, i.p. and the WI rats only exhibiting significant hypothermia after 20 mg/kg, i.p. The antinociceptive effects of inhaled THC (100, 200 mg/mL) did not differ significantly across the strains. These studies confirm an insensitivity of WI rats, compared with SD rats, to hypothermia induced by THC following inhalation conditions that produced identical plasma THC and antinociception. Thus, quantitative, albeit not qualitative, strain differences may be obtained when studying thermoregulatory effects of THC. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Prolonged Hyperglycemia Reduces Elasticity of Type II Diabetic Rat Bone.

An increase in bone fracture risk has been reported in patients with diabetes. To evaluate an early effect of glucose intolerance on bone homeostasis, we have characterized bones from spontaneously diabetic torii (SDT) rats, an animal model of type 2 diabetes in comparison with Sprague Dawley (SD) rats as healthy control. Focusing on early effects of diabetes on bone elasticity, longitudinal wave velocities of animal bones were first determined by a micro-Brillouin scattering technique in a non-destructive way. Wave velocities in the cortical and cancellous bones in the tibias of the SDT and SD rats were compared. In a pre-diabetic stage at approximately 10weeks of age, there seems no significant difference in wave velocities in bones from age-matched SDT and SD rats. By contrast, after the onset of diabetes at approximately 20weeks of age, the mean velocities of bones from SDT rats were lower than those of SD rat. In addition, the X-ray CT showed that the bone amounts of SDT rats were smaller than those of SD rats in an early diabetic stage at 20weeks of age. The current study demonstrated that the wave velocity decreased in bones of SDT rats in the early stages of diabetes. While a decrease of bone strength in an early stage of diabetes can be partially explained from decreases in bone amount as well as bone elasticity, further studies will be needed in understanding a detailed mechanism of bone deterioration due to diabetes.

Collagen-driven remodeling of the intrahepatic duct wall in the PCK rat model of polycystic kidney disease-Caroli syndrome.

Aim of the studyAutosomal dominant polycystic kidney disease (ADPKD) is characterized by formation and expansion of cysts within the kidney. Caroli syndrome (CS) is characterized by cystic saccular dilatation of intrahepatic ducts. Kidney and liver images from a model of ADPKD-CS were evaluated to characterize remodeling of the cystically dilated intrahepatic duct wall and the renal cyst wall.Material and methodsArchival digitized images from Masson’s trichrome-stained renal and Picrosirius red (PSR)-stained renal and hepatic cross-sections were sourced from the PCK rat model of ADPKD-CS, and age-matched Sprague-Dawley rats (wild-type). Cross-sectional areas and wall thicknesses of renal cysts and intrahepatic ducts were measured. Circularly polarized PSR microscopy was utilized to observe accumulation of collagen and identify its subtype.ResultsIn the PCK rat model of ADPKD-CS, renal cysts were relatively thin-walled in comparison to intrahepatic ducts with renal cyst cross-sectional area to wall ratio 47-fold greater than the corresponding ratio in intrahepatic ducts. Increasing intrahepatic duct cross-sectional area was accompanied by a rapid and steep rise in wall thickness. There was a weak but significant direct correlation (r = 0.49, p = 0.037) between renal cyst cross-sectional area and wall thickness. Circularly polarized Picrosirius red microscopy revealed collagen I accumulation within the walls of dilated intrahepatic ducts but not renal cysts.ConclusionsThese data suggest that unlike renal cysts, cystically dilated intrahepatic ducts undergo collagen-driven wall remodeling in the PCK rat.

Combination phosphodiesterase type 4 inhibitor and phosphodiesterase type 5 inhibitor treatment reduces non-voiding contraction in a rat model of overactive bladder.

IntroductionCurrent treatments for overactive bladder (OAB) are often discontinued due to side effects or lack of efficacy. The goal of this study was to determine if combining a phosphodiesterase type 4 inhibitor (PDE4i); with a type 5 inhibitor (PDE5i); would have a beneficial effect on OAB symptoms and if a reduced dose of PDE4i in combination with PDE5i could also provide a beneficial effect in OAB. We hypothesized that PDE5i and PDE4i combination treatment could be utilized to reduce non-voiding contractions and smooth muscle disruption in a rat model of OAB.MethodsFifty-eight age-matched Sprague-Dawley rats underwent PBOO and daily gavage with PDE4i alone (roflumilast; 1mg/kg), PDE5i alone (tadalafil;10mg/kg), high dose combination (PDE4i 1mg/kg, PDE5i 10mg/kg), low dose combination (PDE4i 0.2mg/kg, PDE5i 10mg/kg), or vehicle for 28 days. Fourteen animals underwent sham PBOO with vehicle. Rats underwent conscious and anesthetized cystometry 28 days after PBOO and were euthanized for qualitative bladder histology. One-way ANOVA on ranks with a Dunn’s post hoc test was used to indicate statistically significant differences between groups (p<0.05).ResultsBladder & urethral weight was significantly increased after PBOO with vehicle, PDE4i alone, and PDE5i alone, but not with either combination treatment. Frequency of non-voiding contractions during both conscious and anesthetized cystometry increased significantly after PBOO with vehicle, but not after PDE4i or high dose combination treatments compared to sham PBOO. Threshold pressure for voiding was significantly decreased with high dose combination compared to vehicle. PBOO treated with PDE4i alone or high dose combination showed less bladder smooth muscle fibrosis than vehicle, PDE5i alone, or low dose combination treatments.ConclusionA PDE4i and PDE5i combination treatment has potential benefit in reducing OAB symptoms, but future research is needed.

Role of spinal cord TRAF6/NF-κB signaling pathway in development of diabetic neuropathic pain in rats

Objective To evaluate the role of spinal cord tumor necrosis factor receptor-associated factor 6 (TRAF6)/nuclear factor kappa B(NF-κB)signaling pathway in the development of diabetic neuropathic pain(DNP)in rats. Methods Clean-grade healthy adult male Sprague-Dawley rats, aged 2 months, weighing 180-230 g, in which IT catheters were implanted, were used in this study.Streptozotocin 60 mg/kg was intraperitoneally injected after IT catheterization to establish the model of DNP.Twelve DNP rats were divided into 2 groups (n=6 each) by a random number table method: DNP group and DNP plus TRAF6 inhibitor group (group DTR). Another 6 age-matched Sprague-Dawley rats were used as normal control group(group NC). The rats in group DC and group DTR received IT injection of dimethyl sulfoxide 10 μl and TRAF6 inhibition 10 μg, respectively, once a day for 7 consecutive days starting from day 21 after establishing the model.The mechanical paw withdrawal threshold (MWT) was determined before establishing the model(T1), on 7, 14 and 21 days after establishing the model(T2-4), and on 1, 4 and 7 days after IT injection (T5-7). The rats were sacrificed after the last MWT measurement, and the L3-5 segments of the spinal cord were removed for determination of the expression of TRAF6 and NF-κB p65 by Western blot. Results Compared with group NC, the MWT at T3-7 in group DC and at T3-6 in group DTR was significantly decreased, and the expression of spinal TRAF6 and NF-κB p65 was up-regulated in DC and DTR groups (P<0.05). Compared with group DC, the MWT was significantly increased at T6-7, and the expression of spinal TRAF6 and NF-κB p65 was down-regulated in group DTR (P<0.05). Conclusion Spinal cord TRAF6/NF-κB signaling pathway is involved in the development of DNP in rats. Key words: Spinal cord; Tumor necrosis factor receptor-associated peptides and proteins; NF-kappa B; Diabetes mellitus; Neuralgia

Enhanced renal ischemia-reperfusion injury in aging and diabetes

The incidence and severity of acute kidney injury is increased in patients with diabetes and with aging. However, the mechanisms involved have not been clearly established. The present study examined the effects of aging and diabetes on the severity of renal ischemia-reperfusion (IR) injury in Sprague-Dawley (SD) and type 2 diabetic (T2DN) rats. T2DN rats develop diabetes at 3 mo of age and progressive proteinuria and diabetic nephropathy as they age from 6 to 18 mo. Plasma creatinine levels after bilateral IR were significantly higher (3.4 ± 0.1 mg/dl) in 18-mo-old elderly T2DN rats than in middle-aged (12 mo) T2DN rats with less severe diabetic nephropathy or young (3 mo) and elderly (18 mo) control SD rats (1.5 ± 0.2, 1.8 ± 0.1, and 1.7 ± 0.1 mg/dl, respectively). Elderly T2DN rats exhibited a greater fall in medullary blood flow 2 h following renal IR and a more severe and prolonged decline in glomerular filtration rate than middle-aged T2DN and young or elderly SD rats. The basal expression of the adhesion molecules ICAM-1 and E-selectin and the number of infiltrating immune cells was higher in the kidney of elderly T2DN than age-matched SD rats or young and middle-aged T2DN rats before renal IR. These results indicate that elderly T2DN rats with diabetic nephropathy are more susceptible to renal IR injury than diabetic animals with mild injury or age-matched control animals. This is associated with increased expression of ICAM-1, E-selectin and immune cell infiltration, renal medullary vasocongestion, and more prolonged renal medullary ischemia.

Retinal Vascular Degeneration in the Transgenic P23H Rat Model of Retinitis Pigmentosa.

Retinitis pigmentosa (RP) is a group of inherited retinal degenerative diseases involving a progressive degeneration of photoreceptor cells. Following the loss of photoreceptors, retinal vascularization tends to decrease, which seems to play a role in the degenerative process of retinal cells. This study reports changes in retinal vascular network architecture in the P23H rat model of RP at different stages of retinal degeneration. Homozygous P23H line-3 rats of ages ranging from 18 days to 16 months were used in this study. Age-matched Sprague-Dawley (SD) rats were used as control animals. Vertical sections and wholemount retinas were immunolabeled for type IV collagen or stained using NADPH diaphorase histochemistry, and retinal vascular networks were drawn using a camera lucida. The superficial and deep capillary plexus (DCP) were fully developed at P18 in P23H rat retinas and showed no differences from the control animals. In 4-month-old P23H rat retinas, the superficial and intermediate capillary plexus were similar to those observed in age-matched SD rats, but a reduction in the DCP could be observed in these animals, with a significant decrease in both capillary density and capillary loops. At 16 months, the DCP was completely lost, and only vessels exhibiting an abnormal, tortuous dead-end could be observed. The middle capillary plexus had virtually disappeared at this age. Only perpendicular vessels connecting the superficial and DCP were found. The superficial plexus showed no changes in the vascular surface with age. In RP, photoreceptor loss is accompanied by degenerative changes in the retinal vascular network. The disruption of the capillary plexus, with loss of capillary density and capillary loops, can hamper the normal supply of oxygen and nutrients to retinal cells, thus accelerating retinal degeneration. Therefore, changes in retinal vascularization must be taken into account in the design of therapies targeting retinal degenerative diseases.

MRI Characterization of Age‐Associated Changes to the Cerebral Arteries in a Rodent Model of Aging and Hypertension

Cerebral blood vessel remodeling occurs in response to aging and hypertension. Of importance are structural changes that occur to the circle of Willis and the impact of these changes on blood flow within the brain, especially in regions associated with learning and memory, such as the hippocampus. In the present study, we apply MRI to a rodent model of aging and hypertension to elucidate changes in the circle of Willis during aging and age‐associated hypertension.HypothesisWe hypothesized that arteries comprising the circle of Willis in hypertensive Dahl‐salt sensitive rats (Dahl‐S) will exhibit age‐related volume changes, these changes will impact metabolite levels in the hippocampus and the effects will differ between Dahl‐S and age‐matched Sprague‐Dawley rats (SD).MethodsWhole brain time‐of‐flight (TOF) 3D MRI and MRS (spectroscopy) of the hippocampus were acquired using a 7 Tesla 30 cm Bruker Biospec scanner in SD and Dahl‐S male rats on normal 0.5% NaCl intake at 3, 6 and 12‐mo of age (n=5/group). Cerebral arteries comprising the circle of Willis (cerebral arterial circle (CAC), caudal communicating artery (CCA) and rostral communicating artery (RCA)) were manually segmented using AMIRA. MRS data were processed using LCmodel. Systolic blood pressure (SBP) was measured via the tail‐cuff method at each time point before MRI scans. Data were analyzed using 2‐way ANOVA followed by a Tukey's posthoc test, and are presented as mean ± standard deviationResultsAt 3‐mo, SBP did not differ between Dahl‐S vs SD (134.6±14.1 vs 131.4±8.8 mmHg). However, Dahl‐S had higher SBP vs SD at 6‐mo (165.8±20.6 vs 123.7±8.8 mmHg) and 12‐mo (166.1±16.9 vs 142.2±12.8 mmHg). The CAC volume was greater in SD vs Dahl‐S at 3 and 12‐mo but did not differ at 6‐mo (Table). Importantly, the CAC was not visible by MRI in Dahl‐S at 12‐mo of age, except in one animal. The CCA volume was greater in SD vs Dahl‐S at 12‐mo and did not differ at 3 or 6‐mo. The RCA volume did not differ between strains at any time point. No arterial volume differed with age in SD. In Dahl‐S, the CCA and RCA volumes were larger at 6‐mo compared to 3 and 12‐mo (Table). Total N‐acetylaspartate (NAA) in the hippocampus was lowest at 6‐mo in both strains, compared to 3 and 12‐mo, but did not differ between strains at any time point (Table).ConclusionWe observed variations with strain and age in the volume of arteries in the circle of Willis in normotensive SD and hypertensive Dahl‐S. Hypertensive Dahl‐S at 6‐mo of age may experience increased metabolic demand and blood volume requirements in the brain.Support or Funding InformationThis work was supported solely by the NIH/NIA Intramural Research Program.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Wake-sleep and cardiovascular regulatory changes in rats made obese by a high-fat diet

Obesity is known to be associated with alterations in wake-sleep (WS) architecture and cardiovascular parameters. This study was aimed at assessing the possible influence of diet-induced obesity (DIO) on sleep homeostasis and on the WS state‐dependent levels of arterial pressure (AP) and heart rate in the rat. Two groups of age-matched Sprague-Dawley rats were fed either a high-fat hypercaloric diet, leading to DIO, or a normocaloric standard diet (lean controls) for 8 weeks. While under general anesthesia, animals were implanted with instrumentation for the recording of electroencephalogram, electromyogram, arterial pressure, and deep brain temperature. The experimental protocol consisted of 48h of baseline, 12h of gentle handling, enhancing wake and depressing sleep, and 36-h post-handling recovery. Compared to lean controls, DIO rats showed: i) the same amount of rapid-eye movement (REM) and non-REM (NREM) sleep in the rest period, although the latter was characterized by more fragmented episodes; ii) an increase in both REM sleep and NREM sleep in the activity period; iii) a comparable post-handling sleep homeostatic response, in terms of either the degree of Delta power increase during NREM sleep or the quantitative compensation of the REM sleep loss at the end of the 36-h recovery period; iv) significantly higher levels of AP, irrespectively of the different WS states and of the changes in their intensity throughout the experimental protocol. Overall, these changes may be the reflection of a modification in the activity of the hypothalamic areas where WS, autonomic, and metabolic regulations are known to interact.

Impaired Purinergic Regulation of the Glial (Müller) Cell Volume in the Retina of Transgenic Rats Expressing Defective Polycystin-2.

Retinal glial (Müller) cells possess an endogenous purinergic signal transduction cascade which normally prevents cellular swelling in osmotic stress. The cascade can be activated by osmotic or glutamate receptor-dependent ATP release. We determined whether activation of this cascade is altered in Müller cells of transgenic rats that suffer from a slow photoreceptor degeneration due to the expression of a truncated human cilia gene polycystin-2 (CMV-PKD21/703 HA). Age-matched Sprague-Dawley rats served as control. Retinal slices were superfused with a hypoosmotic solution (60% osmolarity). Müller cells in retinas of PKD21/703 rats swelled immediately in hypoosmotic stress; this was not observed in control retinas. Pharmacological blockade of P2Y1 or adenosine A1 receptors induced osmotic swelling of Müller cells from control rats. The swelling induced by the P2Y1 receptor antagonist was mediated by induction of oxidative-nitrosative stress, mitochondrial dysfunction, production of inflammatory lipid mediators, and a sodium influx from the extracellular space. Exogenous VEGF or glutamate prevented the hypoosmotic swelling of Müller cells from PKD21/703 rats; this effect was mediated by activation of the purinergic signaling cascade. In neuroretinas of PKD21/703 rats, the gene expression levels of P2Y1 and A1 receptors, pannexin-1, connexin 45, NTPDases 1 and 2, and various subtypes of nucleoside transporters are elevated compared to control. The data may suggest that the osmotic swelling of Müller cells from PKD21/703 rats is caused by an abrogation of the osmotic ATP release while the glutamate-induced ATP release is functional. In the normal retina, ATP release and autocrine P2Y1 receptor activation serve to inhibit the induction of oxidative-nitrosative stress, mitochondrial dysfunction, and production of inflammatory lipid mediators, which otherwise will induce a sodium influx and cytotoxic Müller cell swelling under anisoosmotic conditions. Purinergic receptors may represent a target for the protection of retinal glial cells from mitochondrial oxidative stress.

GW26-e5397 Caloric Restriction Ameliorates Angiotensin Induced Mitochondrial Remodeling and Cardiac Hypertrophy

To discuss Caloric Restriction Ameliorates Angiotensin can induced Mitochondrial Remodeling and Cardiac Hypertrophy. We used fourty 4-week-old double transgenic rats (dTGRs) and 16 age-matched normotensive Sprague-Dawley (SD) rats described elsewhere .dTGRs and SD control rats were divided into 4

Duodenal-Jejunal Bypass Surgery Ameliorates Glucose Homeostasis and Reduces Endoplasmic Reticulum Stress in the Liver Tissue in a Diabetic Rat Model.

Duodenal-jejunal bypass (DJB) has been shown to be an effective surgical treatment for type 2 diabetes mellitus (T2DM). However, the underlying mechanisms are poorly understood. Recently, accumulating evidences suggest that endoplasmic reticulum (ER) stress plays an important role in the development of insulin resistance in T2DM. The present study was designed to investigate the effect of DJB on glucose homeostasis, the ER stress state in the liver tissue, and the involving signaling independently of weight loss. Thirty adult male T2DM Sprague-Dawley (SD) rats induced by high-fat diet and low dose of streptozotocin (STZ) were randomly divided into DJB and sham groups. Ten age-matched male SD rats were assigned as the control group. The parameters of body weight and calorie intake were measured at indicated time points. The glucose tolerance and insulin resistance were detected to evaluate the glucose homeostasis. Serum insulin was determined by enzyme-linked immunosorbent assay (ELISA). The markers of ER stress, the activity of c-Jun N-terminal kinase (JNK) and serine phosphorylation of insulin receptor substrate 1 (IRS-1) in the liver tissue, were determined by Western blotting. DJB induced significant improvements in glucose homeostasis and insulin sensitivity, but without weight loss. DJB improved the ER stress state indicated by decreased protein kinase RNA (PKR)-like ER protein kinase (PERK) and inositol-requiring enzyme 1 (IRE-1) phosphorylation in the liver tissue. The JNK activity and serine phosphorylation of IRS-1 in the liver tissue were significantly reduced after DJB. DJB ameliorates glucose homeostasis. Meanwhile, our study helps to reveal that the reduced hepatic ER stress and the decreased JNK activity may contribute to the improved glucose homeostasis after DJB.

Abstract 19288: Pulmonary Hypertension and Sex Hormone Depletion Affect Lung and Right Ventricular Estrogen Receptor Expression

Introduction: Women with pulmonary arterial hypertension exhibit more preserved right ventricular (RV) function than men. The underlying mechanisms are unknown. We measured 17beta-estradiol (E2) levels and lung and RV expression of the two main estrogen receptors (ERalpha and -beta) in male and in intact or ovariectomized (OVX) female rats with Su5416/hypoxia (SuHx)-induced pulmonary hypertension (PH). Hypothesis: E2 is required for adaptation to increased RV afterload in females, and ER expression is inversely correlated with PH severity. Methods: Male and age-matched female Sprague-Dawley rats received Su5416 (20mg/kg), followed by 3 weeks of hypoxia (Patm=362 mmHg) and 4 weeks of room air. Selected females underwent OVX with or without concomitant E2 repletion (75 mcg/kg/d). RV hypertrophy (RV/[LV+S]), RV systolic pressure (RVSP), and PA muscularization were measured; complemented by echocardiographic assessment of RV function and measurement of exercise capacity (VO2max). In addition, we assessed RV pro-apoptotic signaling (bcl-2/bax; caspase-3 activity), serum E2 levels, and lung and RV ER expression by Western blot. N was 7-8/group. P&lt;0.05 was considered significant. Results: While no sex differences were noted in RV/(LV+S), RVSP or PA remodeling, female SuHx rats exhibited more preserved cardiac indices (CI; p&lt;0.05). OVX worsened SuHx-induced alterations in RV hypertrophy, RVSP and CI (p&lt;0.05). In turn, E2 replacement in SuHx-OVX rats prevented SuHx-induced alterations in PH endpoints and RV function; this was accompanied by attenuated RV pro-apoptotic signaling. RV ERbeta decreased in OVX SuHx females, but was restored with E2 repletion (p&lt;0.05). RV ERbeta correlated negatively with RVSP and RV/(LV+S), and positively with RV bcl-2/bax (p&lt;0.05). Similarly, serum E2 levels correlated negatively with RVSP and RV/(LV+S) (p&lt;0.05). While healthy females exhibited higher lung ERbeta than healthy males (p&lt;0.05), no such differences were observed in SuHx-PH. Neither lung nor RV ERalpha was affected by PH or hormone depletion. Conclusions: E2 is required for female adaption to SuHx-PH, through a mechanism that may involve ERbeta-mediated RV cell viability signaling, thus allowing for better adaptation to increases in RV afterload.

Relaxin Does Not Improve Angiotensin II-Induced Target-Organ Damage

Relaxin is a corpus-luteum produced protein hormone with vasodilatatory, anti-fibrotic, and angiogenic properties that are opposite to angiotensin (Ang) II. We investigated whether or not relaxin ameliorates Ang II-induced target-organ damage. We used double transgenic rats harboring both human renin and angiotensinogen genes (dTGR) that develop severe hypertension, target-organ damage, and die untreated within 7–8 weeks. Recombinant relaxin at a low (26 μg/kg/d) and a high dose (240 μg/kg/d) was given to 4 week-old dTGR and age-matched Sprague-Dawley rats (SD). Systolic blood pressure increased progressively in untreated dTGRs from 162±3 mmHg at week 5 to 225±5 mmHg at week 7. Relaxin had no effect on blood pressure whereas SD rats were normotensive (106±1 mmHg). Untreated and relaxin-treated dTGR had similarly severe cardiac hypertrophy indices. Relaxin did not ameliorate albuminuria and did not prevent matrix-protein deposition in the heart and kidney in dTGR. Finally, relaxin treatment did not reduce mortality. These data suggest that pharmacological doses of relaxin do not reverse severe effects of Ang II.

Characterization of diabetic neuropathy in the Zucker diabetic Sprague-Dawley rat: a new animal model for type 2 diabetes.

Recently a new rat model for type 2 diabetes the Zucker diabetic Sprague-Dawley (ZDSD/Pco) was created. In this study we sought to characterize the development of diabetic neuropathy in ZDSD rats using age-matched Sprague-Dawley rats as a control. Rats were examined at 34 weeks of age 12 weeks after the onset of hyperglycemia in ZDSD rats. At this time ZDSD rats were severely insulin resistant with slowing of both motor and sensory nerve conduction velocities. ZDSD rats also had fatty livers, elevated serum free fatty acids, triglycerides, and cholesterol, and elevated sciatic nerve nitrotyrosine levels. The corneas of ZDSD rats exhibited a decrease in subbasal epithelial corneal nerves and sensitivity. ZDSD rats were hypoalgesic but intraepidermal nerve fibers in the skin of the hindpaw were normal compared to Sprague-Dawley rats. However, the number of Langerhans cells was decreased. Vascular reactivity of epineurial arterioles, blood vessels that provide circulation to the sciatic nerve, to acetylcholine and calcitonin gene-related peptide was impaired in ZDSD rats. These data indicate that ZDSD rats develop many of the neural complications associated with type 2 diabetes and are a good animal model for preclinical investigations of drug development for diabetic neuropathy.

Müller Cell Reactivity in Response to Photoreceptor Degeneration in Rats with Defective Polycystin-2

BackgroundRetinal degeneration in transgenic rats that express a mutant cilia gene polycystin-2 (CMV-PKD2(1/703)HA) is characterized by initial photoreceptor degeneration and glial activation, followed by vasoregression and neuronal degeneration (Feng et al., 2009, PLoS One 4: e7328). It is unknown whether glial activation contributes to neurovascular degeneration after photoreceptor degeneration. We characterized the reactivity of Müller glial cells in retinas of rats that express defective polycystin-2.MethodsAge-matched Sprague-Dawley rats served as control. Retinal slices were immunostained for intermediate filaments, the potassium channel Kir4.1, and aquaporins 1 and 4. The potassium conductance of isolated Müller cells was recorded by whole-cell patch clamping. The osmotic swelling characteristics of Müller cells were determined by superfusion of retinal slices with a hypoosmotic solution.FindingsMüller cells in retinas of transgenic rats displayed upregulation of GFAP and nestin which was not observed in control cells. Whereas aquaporin-1 labeling of photoreceptor cells disappeared along with the degeneration of the cells, aquaporin-1 emerged in glial cells in the inner retina of transgenic rats. Aquaporin-4 was upregulated around degenerating photoreceptor cells. There was an age-dependent redistribution of Kir4.1 in retinas of transgenic rats, with a more even distribution along glial membranes and a downregulation of perivascular Kir4.1. Müller cells of transgenic rats displayed a slight decrease in their Kir conductance as compared to control. Müller cells in retinal tissues from transgenic rats swelled immediately under hypoosmotic stress; this was not observed in control cells. Osmotic swelling was induced by oxidative-nitrosative stress, mitochondrial dysfunction, and inflammatory lipid mediators.InterpretationCellular swelling suggests that the rapid water transport through Müller cells in response to osmotic stress is altered as compared to control. The dislocation of Kir4.1 will disturb the retinal potassium and water homeostasis, and osmotic generation of free radicals and inflammatory lipids may contribute to neurovascular injury.

Diabetes mellitus attenuates myocardial preconditioning of desflurane in ischemia-reperfused rat heart

Desflurane has been commonly used in anesthesia that possesses a cardioprotective effect against ischemia-reperfusion. We evaluated whether diabetes mellitus affected desflurane preconditioning induced cardioprotection in ischemia-reperfusion rat hearts in view of pro- and anti-apoptotic signaling pathways and Ca2+ homeostasis. Streptozotocin-induced, diabetic rats and age-matched wild-type Sprague-Dawley rats were subjected to a left anterior descending coronary artery occlusion for 30 min followed by 1 hr of reperfusion. Myocardial infarct size, activities of Akt, ERK1/2, Bcl-2, Bax and cytochrome c, and gene expression influencing Ca2+ homeostasis were examined. Desflurane preconditioning significantly reduced myocardial infarct size compared to ischemia-reperfusion in wild-type rats but not in diabetic rats. In addition, decrease in Akt, ERK1/2, and Bcl-2, and the increase in Bax and cytochrome c by ischemia-reperfusion was reduced by desflurane preconditioning. In diabetic rat hearts, however, desflurane preconditioning failed to recover the phosphorylation state of Akt and ERK1/2 and to repress apoptotic signaling in association with impoverished modulation of abnormal changes in sarcoplasmic reticulum proteins in ischemia-reperfusion rat hearts. These results suggest that diabetes mellitus attenuated desflurane preconditioning against ischemia-reperfusion, which might be associated with reduced recovery of the activities of proteins involved in anti-apoptotic signaling pathways and sarcoplasmic reticulum.