Sex-matched Sprague-Dawley Rats Research Articles

Injection-site Reactions to Sustained-release Meloxicam in Sprague-Dawley Rats.

An extended-release formulation of the NSAID meloxicam (MSR) is used to provide 72 h of continuous analgesia in many species, including rodents. Although standard formulations of meloxicam are frequently used in rats with no observable injection-site reactions, the potential adverse effects from MSR have not been characterized sufficiently nor has a prospective study of these effects been performed in rats. To address this deficiency, we evaluated injection-site reactions after a single subcutaneous administration of MSR (n = 16) or sterile saline (SC, n = 6) in the flank of age- and sex-matched Sprague-Dawley rats. Mass and erythema scores were measured daily for 2 wk, and injection sites were collected for histopathology after euthanasia. Rats were randomly selected for euthanasia at 7 d (n = 12) or 14 d (n = 10) after injection to capture the subacute and chronic phases of mass and erythematic lesion formation. No rats in the SC group developed lesions, whereas all 16 MSR-treated rats developed masses. The median time to first mass in the MSR treatment group was 3 d (95% CI, 2-3 d), and nearly 8 d for erythema (95% CI, 6.7-9.1 d). The trajectory of mass lesion severity showed rapid progression from score 1 at onset (day 2 or 3) to score 2 for almost all animals by day 5 or 6. Histopathology was characterized by localized inflammation with central necrosis and peripheral fibrosis, with some sections showing developing draining tracts. Given the high prevalence and severity of localized skin reactions, MSR analgesia should be considered carefully for Sprague-Dawley rats.

Relationship between Urinary Liver-Type Fatty Acid-Binding Protein (L-FABP) and Sarcopenia in Spontaneously Diabetic Torii Fatty Rats.

Background Type 2 diabetes (T2D) is a known risk factor for diabetic kidney disease (DKD) and sarcopenia in older patients. Because there may be an interaction between DKD and sarcopenia, the aim of the present study is to investigate the relationship between urinary levels of liver-type fatty acid-binding protein (L-FABP) and sarcopenia using a novel rat model of T2D. Methods Male spontaneously diabetic Torii (SDT) fatty rats (n = 5) at 16 weeks of age were used as an animal model of T2D. Age- and sex-matched Sprague-Dawley (SD) rats (n = 7) were used as controls. Urine samples were obtained from the rats, and muscle strength was evaluated with the use of the forelimb grip test at 16, 20, and 24 weeks of age. Serum, kidney, soleus, and extensor digitorum longus (EDL) muscle samples were collected at 24 weeks of age. Urinary L-FABP levels were measured using dedicated enzyme-linked immunosorbent assays. Results Increased urinary L-FABP levels, focal glomerular sclerosis, moderate interstitial inflammation and fibrosis, and accumulation of renal oxidative proteins were significantly observed in the SDT fatty rats, compared to the SD rats. Muscle weight, muscle strength, cross-sectional areas of both type I and type IIb muscle fibers, and increasing rate of muscle strength were significantly decreased in the SDT fatty rats compared to the SD rats at 24 weeks. Urinary L-FABP levels at 20 and 24 weeks were significantly negatively correlated with muscle strength. Urinary L-FABP levels at 16 weeks were significantly negatively correlated with the increasing rate of muscle strength. Conclusions Urinary L-FABP reflects the degree of muscle strength and weight, as well as cross-sectional areas of muscle fibers. Although further clinical study is needed, urinary L-FABP may be useful to monitor the progression of sarcopenia and DKD in T2D patients.

Sacral nerve stimulation prompts vagally-mediated amelioration of rodent colitis.

Neuromodulation based on the vagal anti‐inflammatory reflex has emerged as an exciting therapeutic approach for chronic inflammatory diseases. However, it is unclear whether direct stimulation of the vagus or of pelvic nerves coming from sacral roots, providing the bulk of colonic parasympathetic innervation, is the best approach. We hypothesized that sacral nerve stimulation (SNS) would be an effective treatment for colitis. Age and sex‐matched Sprague‐Dawley rats were administered 5% dextran sulphate sodium (DSS) in drinking water ad libitum for 7 days. A group of rats was sacrificed after DSS treatment, and the remaining rats were randomized to either sham‐SNS or SNS groups, which were performed for 1 hr daily for 10 days. Stimulations were delivered via chronically implanted electrodes using an 8‐channel universal pulse generator. Sacral nerve stimulation promoted recovery of colitis demonstrated by decreased disease activity index, myeloperoxidase activity, tissue TNF‐alpha, and histological scores as well as an increased colonic M2 macrophage population. Heart rate variability analysis demonstrated a decrease in low frequency and increase in high frequency with SNS, corresponding to increased vagal tone. Additionally, plasma pancreatic peptide was increased and norepinephrine was decreased after SNS in colitis while colon tissue acetylcholine was increased with SNS. This is the first study to the best of our knowledge that demonstrates the benefit of SNS with autonomic mediation. SNS alters the expression of inflammatory cytokines and macrophages as well as modulates neurotransmitters involved in systemic inflammation.

The Possibility of Urinary Liver-Type Fatty Acid-Binding Protein as a Biomarker of Renal Hypoxia in Spontaneously Diabetic Torii Fatty Rats

Background: Renal hypoxia is an aggravating factor for tubulointerstitial damage, which is strongly associated with renal prognosis in diabetic kidney disease (DKD). Therefore, urinary markers that can detect renal hypoxia are useful for monitoring DKD. Objective: To determine the correlation between urinary liver-type fatty acid-binding protein (L-FABP) and renal hypoxia using a novel animal model of type 2 diabetes. Methods: Male spontaneously diabetic Torii (SDT) fatty rats (n = 6) were used as an animal model of type 2 diabetes. Age- and sex-matched Sprague-Dawley (SD) rats (n = 8) were used as controls. Body weight, systolic blood pressure, and blood glucose levels were measured at 8, 12, 16, and 24 weeks of age. Urine samples and serum and kidney tissues were collected at 24 weeks of age. Microvascular blood flow index (BFI) was measured using diffuse correlation spectroscopy before sampling both the serum and kidneys for the evaluation of renal microcirculation at the corticomedullary junction. Results: Obesity, hyperglycemia, and hypertension were observed in the SDT fatty rats. Focal glomerular sclerosis, moderate interstitial inflammation, and fibrosis were significantly more frequent in SDT fatty rats than in SD rats. While the frequency of peritubular endothelial cells and phosphoendothelial nitric oxide synthase levels were similar in both types of rats, the degree of renal hypoxia-inducible factor-1α (HIF-1α) expression was significantly higher (and with no change in renal vascular endothelial growth factor expression levels) in the SDT fatty rats. Urinary L-FABP levels were significantly higher and renal microvascular BFI was significantly lower in the SDT fatty rats than in the SD rats. Urinary L-FABP levels exhibited a significant positive correlation with renal HIF-1α expression and a significant negative correlation with renal microvascular BFI. Conclusions: Urinary L-FABP levels reflect the degree of renal hypoxia in DKD in a type 2 diabetic animal model. Urinary L-FABP may thus prove useful as a renal hypoxia marker for monitoring DKD in patients with type 2 diabetes in clinical practice.

Increased activity of the orexin system in the paraventricular nucleus contributes to salt-sensitive hypertension.

The orexin system is involved in arginine vasopressin (AVP) regulation, and its overactivation has been implicated in hypertension. However, its role in salt-sensitive hypertension (SSHTN) is unknown. Here, we tested the hypothesis that hyperactivity of the orexin system in the paraventricular nucleus (PVN) contributes to SSHTN via enhancing AVP signaling. Eight-week-old male Dahl salt-sensitive (Dahl S) and age- and sex-matched Sprague-Dawley (SD) rats were placed on a high-salt (HS; 8% NaCl) or normal-salt (NS; 0.4% NaCl) diet for 4 wk. HS intake did not alter mean arterial pressure (MAP), PVN mRNA levels of orexin receptor 1 (OX1R), or OX2R but slightly increased PVN AVP mRNA expression in SD rats. HS diet induced significant increases in MAP and PVN mRNA levels of OX1R, OX2R, and AVP in Dahl S rats. Intracerebroventricular infusion of orexin A (0.2 nmol) dramatically increased AVP mRNA levels and immunoreactivity in the PVN of SD rats. Incubation of cultured hypothalamus neurons from newborn SD rats with orexin A increased AVP mRNA expression, which was attenuated by OX1R blockade. In addition, increased cerebrospinal fluid Na+ concentration through intracerebroventricular infusion of NaCl solution (4 µmol) increased PVN OX1R and AVP mRNA levels and immunoreactivity in SD rats. Furthermore, bilateral PVN microinjection of the OX1R antagonist SB-408124 resulted in a greater reduction in MAP in HS intake (-16 ± 5 mmHg) compared with NS-fed (-4 ± 4 mmHg) anesthetized Dahl S rats. These results suggest that elevated PVN OX1R activation may contribute to SSHTN by enhancing AVP signaling.NEW & NOTEWORTHY To our best knowledge, this study is the first to investigate the involvement of the orexin system in salt-sensitive hypertension. Our results suggest that the orexin system may contribute to the Dahl model of salt-sensitive hypertension by enhancing vasopressin signaling in the hypothalamic paraventricular nucleus.

Evidence Supporting an Association Between Expression of Major Histocompatibility Complex II by Microglia and Optic Nerve Degeneration During Experimental Glaucoma.

We acquired age-matched and sex-matched Sprague-Dawley rats from 2 independent breeding establishments. Serendipitously, we observed that constitutive, and bacterial toxin-induced, expression of major histocompatibility complex (MHC) class II RT1B chain in the uveal tract was much lower in one of the cohorts. Activated microglia are known to upregulate MHC II RT1B expression during optic nerve (ON) degeneration induced by raised intraocular pressure (IOP). We investigated whether, in a model of experimental glaucoma, microglial upregulation of MHC II RT1B was less efficacious and ON degeneration correspondingly less severe in the cohort of rats with low MHC II RT1B expression. Experimental glaucoma was induced by lasering the trabecular meshwork using a standard protocol. After 2 weeks of elevated IOP, retinal ganglion cells (RGC) survival, ON degeneration, and microglial responses were determined in both cohorts of rats. Raised IOP-induced expression of MHC II RT1B by microglia was muted in the "Low" cohort compared with the "High" cohort. Axonal degeneration, RGC loss, and microgliosis were all significantly lower in the cohort of rats with low basal and induced expression of MHC II RT1B, despite both cohorts displaying IOP responses that were indistinguishable in terms of peak IOP and IOP exposure. Expression of MHC II RT1B by activated microglia in the ON during experimental glaucoma was associated with more severe RGC degeneration. Further studies are needed to elucidate the role of MHC II during experimental glaucoma.

Regulation of Aldosterone Biosynthesis by Adrenal Renin Is Mediated Through AT 1 Receptors in Renin Transgenic Rats

The transgenic (TG) rat (mREN2)27 is characterized by overexpression of the additional mouse Ren-2d gene in the adrenal cortex with marked suppression of renal renin. We have previously shown that in salt-depleted TG rats enhanced activation of mineralocorticoid biosynthesis is associated with selective stimulation of adrenal renin. To investigate whether the local renin-angiotensin system regulates aldosterone biosynthesis in the adrenal cortex of TG rats, we studied the effects of the AT1-angiotensin subtype receptor antagonist DuP 753 on aldosterone production in 5-week-old TG rats during salt restriction. All the rats (n = 56) were shifted from regular chow to a diet containing only 0.04% NaCl for 1 week. The AT1-receptor antagonist DuP 753 (10 mg/kg per day in drinking water) was administered to 27 of these rats during low-salt diet. Subgroups of rats were killed at 0,4, and 7 days. Low-salt diet increased both adrenal renin activity (from 31 +/- 3 to 77 +/- 4 and 85 +/- 2 ng angiotensin I.h-1.mg protein-1 at 4 and 7 days, respectively; P < .001) and mRNA (by 68.4 +/- 10% and 80 +/- 17% from baseline, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin and bradykinin peptides in the TGR(mRen-2)27 rat.

The transgenic TGR(mRen-2)27 rat, in which the Ren-2 mouse renin gene is transfected into the genome of the Sprague-Dawley rat, develops severe hypertension at a young age that responds to inhibitors of angiotensin-converting enzyme and to antagonists of the type 1 angiotensin II (Ang II) receptor. Despite this evidence that the hypertension is Ang II dependent, TGR(mRen-2)27 rats have suppressed renal renin and renin mRNA content, and there is controversy concerning the plasma levels of renin and Ang II in these rats. We investigated the effect of the transgene on circulating and tissue levels of angiotensin and bradykinin peptides in 6-week-old male homozygous TGR(mRen-2)27 rats. Systolic blood pressure of TGR(mRen-2)27 rats was 212 +/- 4 mm Hg (mean +/- SEM, n = 25) compared with 108 +/- 2 mm Hg (n = 29) for age- and sex-matched Sprague-Dawley rats. Compared with control rats, TGR(mRen-2)27 rats had increased plasma levels of active renin (4.5-fold), prorenin (300-fold), and Ang II (fourfold) as well as tissue levels of Ang II (twofold to fourfold in kidney, adrenal, heart, aorta, brown adipose tissue, and lung and 18-fold in brain). Plasma angiotensinogen levels were reduced to 73% of control, and plasma aldosterone levels were increased fourfold. Plasma angiotensin-converting enzyme was reduced to 64% of control. Compared with control rats, TGR(mRen-2)27 rats had increased bradykinin levels in brown adipose tissue (1.9-fold) and lung (1.6-fold).(ABSTRACT TRUNCATED AT 250 WORDS)

Zona glomerulosa of the adrenal gland in a transgenic strain of rat: a morphologic and functional study

Transgenic rats for the murine Ren-2 gene display high blood pressure, low circulating levels of angiotensin II, and high renin content in the adrenal glands. Moreover, transgenic rats possess an increased aldosterone secretion (maximal from 6 to 18 weeks of age), paralleling the development of hypertension. To investigate further the cytophysiology of the adrenal glands of this strain of rats, we performed a combined morphometric and functional study of the zona glomerulosa of 10-week-old female transgenic rats. Morphometry did not reveal notable differences between zona glomerulosa cells of transgenic and age- and sex-matched Sprague-Dawley rats, with the exception of a marked accumulation of lipid droplets, in which cholesterol and cholesterol esters are stored. The volume of the lipid-droplet compartment underwent a significant decrease when transgenic rats were previously injected with angiotensin II or ACTH. Dispersed zona glomerulosa cells of transgenic rats showed a significantly higher basal aldosterone secretion, but their response to angiotensin II and ACTH was similar to that of Sprague-Dawley animals. Angiotensin II-receptor number and affinity were not dissimilar in zona glomerulosa cells of transgenic and Sprague-Dawley rats. These data suggest that the sustained stimulation of the adrenal renin-angiotensin system in transgenic animals causes an increase in the accumulation in zona glomerulosa cells of cholesterol available for steroidogenesis, as indicated by the expanded volume of the lipid-droplet compartment and the elevated basal steroidogenesis. However, the basal hyperfunction of the zona glomerulosa in transgenic animals does not appear to be coupled with an enhanced responsivity to its main secretagogues, at least in terms of aldosterone secretion.

Thymus dependence of compound 48/80-induced mucosal mast cell proliferation.

The mucosal and connective-tissue mast cells (MMC and CTMC, respectively) of the rat are histochemically and functionally distinct. MMC, unlike CTMC, are insensitive to the degranulating action of the mast cell secretagogue Compound 48/80 and instead increase in number after treatment with this drug. T cell-derived growth factors are necessary for the growth of MMC-like cells from hemopoietic tissues in vitro, as well as for nematode-induced MMC proliferation in vivo. We therefore examined the possible role of the thymus in the pharmacologically induced MMC expansion. Mast cell numbers and histamine content after treatment with Compound 48/80 were determined in the skin, tongue and gut of athymic male LEW/MOL-rnu/rnu rats and their normal littermates at the age of 6-7 weeks. The influence of the strain of rat and the mode of administration of the drug was assessed by studying age- and sex-matched Sprague-Dawley rats as well. Injections of Compound 48/80 for 5 days resulted in a statistically significant increase in the number of intestinal MMC and the histamine content of all thymus-bearing rats. The increase was more pronounced in the Sprague-Dawley rats, however, and unrelated to the mode of administration of the drug, indicating that the MMC-stimulating action of Compound 48/80 is at least partly controlled by genetic factors. Athymic rats showed no statistically significant MMC expansion. This suggests that the MMC response after Compound 48/80 treatment may be at least partly dependent on the thymus. The mast cell numbers and histamine content in the tissues of athymic control rats were higher than in their thymus-bearing littermates.(ABSTRACT TRUNCATED AT 250 WORDS)