Lung Angiotensin Converting Enzyme Activity Research Articles

Ratiometric fluorescence detection of the angiotensin-converting enzyme via single-excitation and double-emission biomass-derived carbon quantum dots

Efficient and rapid detection of angiotensin-converting enzyme (ACE) activity is important for preventing hypertension and the discovery of new angiotensin-converting enzyme inhibitors (ACEI). In this work, a single-excitation and double-emission biomass-derived carbon quantum dots (CQDs) was prepared and applied for ratiometric fluorescence detection of ACE. Fresh banyan leaves were extracted with ethanol and acetone, and the extracted solution was used as the precursor to produce the carbon quantum dots (BL-CQDs) with single-excitation and double-emission properties. The synthesized BL-CQDs is about 1.7 nm, has a graphene-like structure, contains a variety of hydrophilic functional groups on the surface, and has good fluorescence properties. Its fluorescence intensity ratio (I677/I460) is linear with ACE activity in the range of 0.02–0.8 U l−1. The regression equation is △F=2.5371 C ACE -0.0311. The method was successfully applied to the determination of ACE activity in pig lung and human serum, and the inhibitory efficiency of the flavonoid extract and captopril tablets on ACE activity was also investigated, which can be applied to the screening of ACEI. The survival rate and fluorescence imaging of Bel-7404 cells under the condition of high concentration BL-CQDs showed BL-CQDs had low cytotoxicity and good biocompatibility. These results indicate that the BL-CQDs can be used as an excellent fluorescent probe, providing a new method for screening ACE activity and plant-derived ACEI.

AN IN VITRO STUDY OF CINNAMOMUM ZEYLANICUM AS NATURAL INHIBITOR OF ANGIOTENSIN-CONVERTING ENZYME (ACE) ON SHEEP (OVIS ARIES) TISSUES

ABSTRACTObjective: The present study was aimed to find the angiotensin-converting enzyme (ACE) inhibitory activity using the methanolic extract ofCinnamomum zeylanicum (as a natural inhibitor) on sheep tissues as the enzyme source.Methods: Hippuryl-histidyl-leucine (HHL) as a substrate, tissue ACE activity was measured spectrophotometrically at 228 nm. For an incubationperiod of 30 minutes at 37°C, the linearity of ACE activity of kidney, lung, and testis enzyme was established. A known medicinal plant C. zeylanicumwas used as natural inhibitor of ACE. In this enzyme assay, inhibitory effect of methanolic extract of C. zeylanicum on kidney, lung and testicular ACEwas determined. ACE activity was confirmed by captopril, a standard inhibitor of ACE.Results: In the presence of a methanolic extract of C. zeylanicum (10:1), ACE activity was determined and this has inhibited ACE activity verysignificantly. C. zeylanicum leaves extract has reduced sheep kidney, lung, and testis ACE activity by 70.06%, 12.63%, and 20.23%, respectively.Conclusion: Significant inhibition was observed in the kidney ACE than in lung and testis ACE activity. This can propose that there may be a possiblerole in controlling blood pressure or reduction in cardiovascular diseases. Some plants with the great medicinal property may be considered aspromising sources of natural inhibitors of ACE for medicine and commercial uses. This comprehensive study may show numerous beneficial effects asa potential therapeutic agent for lowering blood pressure.Keywords: Angiotensin-converting enzyme, Natural angiotensin-converting enzyme inhibitor, Kinetic assay, Hippuryl-histidyl-leucine, Cinnamomumzeylanicum, Cardiovascular diseases.

Acute Cadmium Exposure Reduces the Local Angiotensin I Converting Enzyme Activity and Increases the Tissue Metal Content.

Cadmium exposure causes health problems that may result from increased oxidative stress and from changes in enzyme metalloproteases activities as angiotensin-converting enzyme (ACE). In fact, cadmium produces inhibition of serum ACE but is not known how cadmium acts on tissue ACE activity and whether following acute exposure tissue cadmium content is increased. In order to elucidate these issues, a cadmium bolus was injected intravenously in Wistar rats, and the cadmium content and the ACE activity were measured in the serum, lungs, aorta and kidneys. Moreover, in order to clarify if the cadmium affects directly tissue ACE activity, acute metal exposure in vitro was performed. Our results demonstrated that 120min following cadmium administration, blood and organ cadmium content were both increased. Serum and lung ACE activity were reduced following acute cadmium exposure, but aortic and kidney ACE activities were not affected. The inhibitory effects induced by cadmium on ACE activity were also observed in the serum, as well as the lungs and the aorta, but not in the kidneys following in vitro exposure. Moreover, the inhibitory effects induced by cadmium on ACE activity were partially restored in vitro by zinc supplementation, suggesting a possible interaction or competition between cadmium and zinc by at the active site of ACE. Summarising, our results suggest that acute cadmium exposure promotes an increase in the tissue metal content that was accompanied by direct inhibition of serum, aorta and lung ACE activity, an effect that is cadmium concentration-dependent and is partially reversed by zinc.

Mitigation of radiation induced pulmonary vascular injury by delayed treatment with captopril

A single dose of 10 Gy radiation to the thorax of rats results in decreased total lung angiotensin-converting enzyme (ACE) activity, pulmonary artery distensibility and distal vascular density while increasing pulmonary vascular resistance (PVR) at 2 months post-exposure. In this study, we evaluate the potential of a renin-angiotensin system (RAS) modulator, the ACE inhibitor captopril, to mitigate this pulmonary vascular damage. Rats exposed to 10 Gy thorax only irradiation and age-matched controls were studied 2 months after exposure, during the development of radiation pneumonitis. Rats were treated, either immediately or 2 weeks after radiation exposure, with two doses of the ACE inhibitor, captopril, dissolved in their drinking water. To determine pulmonary vascular responses, we measured pulmonary haemodynamics, lung ACE activity, pulmonary arterial distensibility and peripheral vessel density. Captopril, given at a vasoactive, but not a lower dose, mitigated radiation-induced pulmonary vascular injury. More importantly, these beneficial effects were observed even if drug therapy was delayed for up to 2 weeks after exposure. Captopril resulted in a reduction in pulmonary vascular injury that supports its use as a radiomitigator after an unexpected radiological event such as a nuclear accident.

Evaluation of Antihypertensive and Antihyperlipidemic Effects of Bamboo Shoot Angiotensin Converting Enzyme Inhibitory Peptide in Vivo

Cardiovascular protective functions of bamboo shoot angiotensin converting enzyme (ACE) inhibitory peptide (BSP) from bamboo shoot were evaluated, including antihypertensive effect on spontaneously hypertensive rats (SHRs) and antihyperlipidemic effect on high-fat-diet-induced rats. Thirty-day antihypertensive effects of BSP on SHRs were assayed. Asp-Tyr [10 mg/day kg body weight (BW)] and BSP (50 mg/day kg BW) significantly reduced ACE activity in lung at the same level (p < 0.05), while BSP (50 mg/day kg BW) reduced systolic blood pressure (SBP) more effectively for its phenolic compounds, such as ferulic acid and p-coumaric acid, which when combined with ACE inhibitor exert a synergistic effect. BSP could significantly reduce SBP, improve oxidant stress status (GSH-Px, SOD, TAC and MDA), and increase NO level in serum and NOS activity in kidney. BSP decreased total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-c) content and MDA level of hyperlipidemic rats, which might contribute to the ACE inhibitory capacity of Asp-Tyr and the fatty acid synthase inhibitory activity of phenolic compounds.

Losartan exerts no protective effects against acute pulmonary embolism-induced hemodynamic changes

The acute obstruction of pulmonary vessels by venous thrombi is a critical condition named acute pulmonary embolism (APE). During massive APE, severe pulmonary hypertension may lead to death secondary to right heart failure and circulatory shock. APE-induced pulmonary hypertension is aggravated by active pulmonary vasoconstriction. While blocking the effects of some vasoconstrictors exerts beneficial effects, no previous study has examined whether angiotensin II receptor blockers protect against the hemodynamic changes associated with APE. We examined the effects exerted by losartan on APE-induced hemodynamic changes. Hemodynamic evaluations were performed in non-embolized lambs treated with saline (n = 4) and in lambs that were embolized with silicon microspheres and treated with losartan (30 mg/kg followed by 1 mg/kg/h, n = 5) or saline (n = 7) infusions. The plasma and lung angiotensin-converting enzyme (ACE) activity were assessed using a fluorometric method. APE increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) by 21 ± 2 mmHg and 375 ± 20 dyn s cm⁻⁵ m⁻², respectively (P < 0.05). Losartan decreased MPAP significantly (by approximately 15%), without significant changes in PVRI and tended to decrease cardiac index (P > 0.05). Lung and plasma ACE activity were similar in both embolized and non-embolized animals. Our findings show evidence of lack of activation of the renin-angiotensin system during APE. The lack of significant effects of losartan on the pulmonary vascular resistance suggests that losartan does not protect against the hemodynamic changes found during APE.

Cyclosporin A treatment enhances angiotensin converting enzyme activity in lung and serum of rats

Nephrotoxicity and arterial hypertension are the most common side effects of treatment with cyclosporin A (CSA). Its effects on angiotensin converting enzyme (ACE) activity in the renal cortex, lung and serum of nephrotoxic rats have been investigated. Wistar rats were treated with CSA (20 mg kg-1 day-1 i.p.) or vehicle (olive oil containing 10% ethanol) for 14 days. On day 15, the rats were killed and ACE activity determined by radiometric assay using [3H]hippuryl-glycyl-glycine as substrate. CSA treatment resulted in a decrease in creatinine clearance, urine flow and body weight and a significant increase in serum and lung ACE activities (436 +/- 9 vs 391 +/- 7 nmol mL-1 min-1, P less than 0.001; 184 +/- 8 vs 142 +/- 10 nmol mg-1 min-1 P less than 0.01, respectively). In contrast, renal cortex ACE activity was reduced in the CSA-treated rats (0.35 +/- 0.02 vs 0.51 +/- 0.02 nmol mg-1 min-1, P less than 0.01). ACE activities in the renal cortex and serum were not affected by treatment with gentamicin (80 mg kg-1 day-1) for 11 days. In rats treated simultaneously with CSA and captopril (50 mg kg-1 day-1) ACE activity in the serum, lung and renal cortex was inhibited by 95, 93 and 92%, respectively. These changes in ACE activity were associated with a decreased systolic blood pressure in the rats receiving CSA and captopril. Therefore, ACE activity in the serum and lung of CSA-treated rats was increased, while its activity in the renal cortex was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Maternal low-protein diet during mouse pre-implantation development induces vascular dysfunction and altered renin–angiotensin-system homeostasis in the offspring

Environmental perturbations during early mammalian development can affect aspects of offspring growth and cardiovascular health. We have demonstrated previously that maternal gestational dietary protein restriction in mice significantly elevated adult offspring systolic blood pressure. Therefore, the present study investigates the key mechanisms of blood pressure regulation in these mice. Following mating, female MF-1 mice were assigned to either a normal-protein diet (NPD; 18 % casein) or an isocaloric low-protein diet throughout gestation (LPD; 9 % casein), or fed the LPD exclusively during the pre-implantation period (3.5 d) before returning to the NPD for the remainder of gestation (Emb-LPD). All offspring received standard chow. At 22 weeks, isolated mesenteric arteries from LPD and Emb-LPD males displayed significantly attenuated vasodilatation to isoprenaline (P = 0.04 and P = 0.025, respectively), when compared with NPD arteries. At 28 weeks, stereological analysis of glomerular number in female left kidneys revealed no significant difference between the groups. Real-time RT-PCR analysis of type 1a angiotensin II receptor, Na+/K+ ATPase transporter subunits and glucocorticoid receptor expression in male and female left kidneys revealed no significant differences between the groups. LPD females displayed elevated serum angiotensin-converting enzyme (ACE) activity (P = 0.044), whilst Emb-LPD males had elevated lung ACE activity (P = 0.001), when compared with NPD offspring. These data demonstrate that elevated offspring systolic blood pressure following maternal gestational protein undernutrition is associated with impaired arterial vasodilatation in male offspring, elevated serum and lung ACE activity in female and male offspring, respectively, but kidney glomerular number in females and kidney gene expression in male and female offspring appear unaffected.

Vascular Injury After Whole Thoracic X-Ray Irradiation in the Rat

To study vascular injury after whole thoracic irradiation with single sublethal doses of X-rays in the rat and to develop markers that might predict the severity of injury. Rats that received 5- or 10-Gy thorax-only irradiation and age-matched controls were studied at 3 days, 2 weeks, and 1, 2, 5, and 12 months. Several pulmonary vascular parameters were evaluated, including hemodynamics, vessel density, total lung angiotensin-converting enzyme activity, and right ventricular hypertrophy. By 1 month, the rats in the 10-Gy group had pulmonary vascular dropout, right ventricular hypertrophy, increased pulmonary vascular resistance, increased dry lung weights, and decreases in total lung angiotensin-converting enzyme activity, as well as pulmonary artery distensibility. In contrast, irradiation with 5 Gy resulted in only a modest increase in right ventricular weight and a reduction in lung angiotensin-converting enzyme activity. In a previous investigation using the same model, we observed that recovery from radiation-induced attenuation of pulmonary vascular reactivity occurred. In the present study, we report that deterioration results in several vascular parameters for </=1 year after 10 Gy, suggesting sustained remodeling of the pulmonary vasculature. Our data support clinically relevant injuries that appear in a time- and dose-related manner after exposure to relatively low radiation doses.

Maternal Protein Restriction During Mouse Preimplantation Development Induces Vascular Dysfunction and Altered Renin-angiotensin-system Homeostasis in the Offspring.

Studies using rodent and domestic animal models have demonstrated that environmental conditions experienced during early development, either in vivo or in vitro, shape critical aspects of future growth, metabolism, physiology and cardiovascular health. In particular, we have previously demonstrated that maternal dietary protein restriction during discrete windows of gestation results in the development of hypertension in the adult mouse. Therefore, the aim of the current study was to investigate the potential mechanisms involved in the development of hypertension following maternal protein underntrtion. Following mating, virgin female MF-1 mice were randomly assigned to either normal protein diet for the entirety of gestation (NPD; 18% casein), isocaloric low protein diet for the entirety of gestation (LPD; 9% casein), or LPD exclusively during the preimplantation period (3.5 days), before returning to NPD for the remainder of gestation (Emb-LPD). At birth all litters were standardised to a mean of 6 (3 male and 3 females where possible). At 22 weeks of age, isolated mesenteric arteries from LPD and Emb-LPD males displayed attenuated responsiveness to the endothelial-independent vasodilator isoprenaline (P <0.04) and a trend towards an impaired responsiveness to the nitric oxide donor sodium nitroprusside (P <0.01) when compared to NPD arteries. At 28 weeks of age, female left kidneys were processed in glycol methacrylate, sectioned and, using stereological techniques, glomerular number was estimated using the physical fractionator principle. No difference was observed in mean female left kidney glomerular number between any of the treatment groups. LPD females displayed a significantly elevated serum angiotensin converting enzyme (ACE) activity (P =0.05), while Emb-LPD males and females had a significantly elevated lung ACE activity when compared to NPD offspring (P <0.05). These data demonstrate that maternal dietary protein restriction during discrete windows of gestation (preimplantation development, 3.5 days) programmes postnatal cardiovascular abnormalities through the development of vasodilator dysfunction in male resistance arteries, elevated ACE activity, but with minimal effects on kidney morphology.

Angiotensin‐converting enzyme activity in plasma and tissues of spontaneously hypertensive rats after the short‐ and long‐term intake of hydrolysed egg white

This paper evaluates the effects of the short- (1 g/kg) and long-term (0.5 and 1 g/kg/day) oral intake of egg white hydrolysed with pepsin (hEW) and the long-term oral intake (1 g/kg/day) of egg white (EW) on local angiotensin-converting enzyme (ACE) activities in plasma and other tissues of spontaneously hypertensive rats (SHR), as compared to the effect of the ACE inhibitor prototype captopril. The rats treated with hEW were classed in a different group than the control rats and the rats treated with EW by cluster analysis, taking into account their tissue ACE activities and their systolic blood pressure (SBP). Principal component analysis (PCA) showed that SBP in SHR was negatively related with ACE activity in plasma and positively related with ACE activity in aorta and kidney. ACE activity in plasma significantly increased after the long-term treatment with hEW (0.5 g/kg/day). ACE activity in aorta and kidney was significantly inhibited 4 h after the short-term administration of hEW. The long-term treatment with hEW caused local effects on ACE activity in aorta, kidney and lungs that followed a pattern similar, but less pronounced, than that caused by captopril.

Early lung injury contributes to lung fibrosis via AT1 receptor in rats

Angiotensin II is believed to play an important role in tissue repair and remodeling in lungs by the angiotensin type I (AT1) receptor via a number of potential mechanisms. However, the role of the AT1 receptor in early lung injury has not been characterized. Bleomycin-induced pulmonary fibrosis (PF) in rats was utilized to value the treatment with valsartan, an AT1 receptor antagonist, by measurement of body weight, wet weight of the left lung, hydroxy-proline content, mRNA expression of collagen I/III, and the degree of fibrosis in lung tissues on d 21. Tissue injury in the early phase was assessed on d 1, 3 and 7 by apoptosis, malondialdehyde content, myeloperoxidase activity, inflammatory cell count and protein content. Angiotensin converting enzyme (ACE) activity and the AT1 receptor in lung tissues were analyzed by biochemistry method and Western blotting, respectively. Valsartan ameliorated PF induced by bleomycin in the rats on d 21. After bleomycin was injected intratracheally, increases in the lung AT1 receptor and ACE activity were observed by d 1, 3 and 7. Lung injury deteriorated in the early phase. Valsartan reduced the increase of the AT1 receptor, ACE activity and lung injury induced by bleomycin in the early phase. These observations suggest that angiotensin II may play a potent role in early lung injury via the AT1 receptor. AT1 receptor antagonists should be assessed as potential new therapies for fibrotic lung disease.

Transforming growth factor-β1 upregulation is independent of angiotensin in paraquat-induced lung fibrosis

Transforming growth factor-β1 (TGF-β1) contributes to the fibrosis of injured organs. Angiotensin II (Ang II) is an inducer of TGF-β1 in cells of the heart and kidneys, and the regulation of TGF-β1 by Ang II has not yet been confirmed in lung tissue. We evaluated the role of TGF-β1 and its relationship with Ang II in paraquat-induced lung fibrosis. Adult male Sprague–Dawley rats were treated intraperitoneally with paraquat (20 mg/kg) or saline in the control group. On days 1, 3, 7, and 21 after paraquat treatment, TGF-β1 and collagen gene expressions, TGF-β1 protein, angiotensin-converting enzyme (ACE) activity, Ang II, and hydroxyproline contents were measured in lung tissue. Lung TGF-β1 mRNA expression progressively increased and reached a peak on day 7 after paraquat treatment. Increases in TGF-β1 mRNA expression and TGF-β1 levels preceded the onset of increased collagen I mRNA expression and hydroxyproline contents. c-myc mRNA expressions were inversely correlated with TGF-β1 protein levels in paraquat-treated lungs. Lung ACE activity decreased after paraquat administration and the decrement was maximal on day 7. Lung Ang II concentrations immediately decreased after paraquat administration and the values were not related to TGF-β1 levels. We conclude that TGF-β1 is upregulated and contribute to the paraquat-induced lung fibrosis and this effect is independent of the renin–angiotensin system.

Investigation of local ACE activity and structural alterations during development of l-NAME-induced hypertension

Tonic basal release of nitric oxide (NO) by vascular endothelial cells controls blood pressure (BP) in the basal state. In the present study, we showed how serum and local angiotensin converting enzyme (ACE) alters during development of hypertension in chronic nitric oxide synthase blockade, a non-renin-dependent model of hypertension. Four experiments were performed in which animals were given N ω-nitro- l-arginine methyl ester ( l-NAME) (50 mg kg −1) for 2, 4, 8 and 12 weeks. The control group rats received tap water. The ACE activity in serum, aorta, heart, kidney and lung was analyzed by high performance liquid chromatography (HPLC) and the structural change in aorta was investigated by measurement of cross-sectional area (CSA). Significant elevation of systolic blood pressure developed in chronically NO-blocked rats compared to controls. These results indicated that ACE activity in aortae and heart was gradually increased during development of hypertension and was more pronounced at higher blood pressure. Furthermore, there was a positive correlation between aortic cross-sectional area and elevation of blood pressure. These observations highlight the importance of the local ACE particularly in organs regulating hypertension (aorta and heart) during development of l-NAME-induced hypertension.

Selective rat lung endothelial targeting with a new set of monoclonal antibodies to angiotensin I-converting enzyme

We demonstrated previously that monoclonal antibody (mAb) 9B9 to angiotensin-converting enzyme (ACE) accumulates selectively in the rat lung after systemic injection and thus is a powerful tool for immunotargeting therapeutic agents/genes to the lung microvasculature. Bearing in mind the tremendous research and therapeutic potential of lung immunotargeting via ACE, we generated a novel set of mAbs to rat ACE in order to enhance the repertoire of mAbs suitable for targeting drugs/genes to the rat lung. Five new mAbs recognizing different epitopes on rat ACE were examined for their efficacy to bind rat ACE both in vitro and in vivo. Gene delivery into cultured rat lung endothelial cells increased 30–50-fold after coating modified adenoviruses (containing Ig-binding domain) with mAbs to rat ACE. Radiolabeled mAbs specifically accumulated in the lung after systemic injection. mAb 1A2, 4H3 and 2E1 demonstrated the highest efficacy of lung uptake-around 50% of injected dose per gram of tissue; for mAb 1A2, the selectivity of lung uptake (ratio of lung to blood radioactivity) was 205. The effect of the mAbs on ACE shedding was epitope-specific: injection of mAb 1A2 and 4H3 did not change lung ACE activity, whereas injection of mAb 2E1 and 9B9 decreased rat lung ACE activity by 20%. None of the tested mAbs inhibited ACE activity in vitro. A new set of mAbs to rat ACE demonstrated highly efficient and selective lung accumulation and thus have the potential for targeting drugs/genes to the pulmonary vasculature in different rat models of lung diseases.

Increased blood pressure in the offspring of diabetic mothers

Studies were conducted in rats to determine the effect of maternal diabetes and the consequent hyperglycemia on cardiovascular function in the offspring. Diabetes was induced in pregnant Wistar rats through streptozotocin injection (50 mg/kg). Cardiovascular parameters were measured in 2-mo-old offspring animals of diabetic (OD, n=12) and control rats (OC, n=8). Arterial pressure (AP), heart rate (HR), baroreflex sensitivity, and vascular responsiveness to phenylephrine (PH) and sodium nitroprusside (SN) were measured. Angiotensin-converting enzyme (ACE) activity in heart, kidney, and lung was determined. OD rats exhibited increases in systolic AP (138+/-8 vs. 119+/-6 mmHg, OD vs. OC), with no change in HR (342+/-21 vs. 364+/-39 beats per minute (bpm), OD vs. OC). The reflex tachycardia elicited by SN was reduced in OD rats, as indicated by the slope of the linear regression (-2.2+/-0.4 vs. -3.6+/-0.8 bpm/mmHg, OD vs. OC). Vascular responsiveness to PH was increased 63% in OD rats compared with OC. OD rats showed increases in ACE activity in heart, kidney, and lung (1.13+/-0.24, 3.04+/-0.86, 40.8+/-8.9 vs. 0.73+/-0.19, 1.7+/-0.45, 28.1+/-6 nmol His-Leu.min-1 mg protein-1, OD vs. OC). Results suggest that diabetes during pregnancy affects cardiovascular function in offspring, seen as hypertension, baroreflex dysfunction, and activation of tissue renin-angiotensin system.

Soyabean protein hydrolysate prevents the development of hypertension in spontaneously hypertensive rats.

The aim of the present study was to investigate the anti-hypertensive and angiotensin-converting enzyme (ACE) inhibition effects of soyabean protein hydrolysate in spontaneously hypertensive rats (SHR). Soyabean protein hydrolysate was prepared by peptic hydrolysis and was added into the feed of SHR (0% for the S0 group, 0.5% for the S1 group, and 1% for the S2 group) for 12 weeks. Systolic blood pressure and mean blood pressure of the S1 (164.3 (sem 4.7); 128.0 (sem 5.0) mmHg) and S2 (156.8 (sem 1.6); 120.8 (sem 3.4) mmHg) groups were significantly lower than those of the S0 group (199.4 (sem 5.2); 158.3 (sem 7.0) mmHg) at the end of the study. In the analysis of ACE activity, plasma and heart ACE activities of the S1 and S2 groups were significantly lower than those of the S0 group, and there were no significant differences in aorta, kidney, and lung ACE activities among all SHR. Soyabean protein hydrolysate had no significant effect on plasma lipids, electrolytes, or on left ventricular wall or aorta wall thickness. The results suggest that the long-term administration of soyabean protein hydrolysate might retard the development of hypertension in SHR by its inhibitory effect on ACE in vivo.

Seasonal changes in angiotensin converting enzyme activity in male and female frogs ( Rana esculenta)

Gonad, lung, kidney and serum angiotensin converting enzyme (ACE) activities were determined by specific substrate hydrolysis in male and female Rana esculenta over 1 year. Ovary ACE activity showed the highest values among the different tissues, with a significant peak (223±52 nmol min −1 mg protein −1) in late winter-early spring. Testis ACE activity followed a significant seasonal cycle, increasing from September to peak in April (2.5±0.8 nmol min −1 mg protein −1) and then decreased in the post-reproductive period. Lung and kidney ACE activities were not correlated with the annual reproductive cycle phases. In serum a peak of activity was present in the post-reproductive period both in male and female frogs. The present data show a correlation between ACE and the annual reproductive cycle of R. esculenta.

Study of Serum and Tissues Angiotensin Converting Enzyme (ACE) Activity in Rat with Gentamicin Induced Renal Toxicity

Purpose. In this research ACE activity (as a marker of epithelial injury) was studied in rats with gentamicin induced renal toxicity. Methods. Male Sprague-Dawley rats were sacrificed 1, 3, 5, and 7 days after gentamicin injection, 100 mg/kg/day for 1, 3, 5, and 7 consecutive days. ACE activity was measured in serum, kidney and lung. These data were compared with normal saline-treated rats. Histological scoring of renal cortical pathology was performed on days 1, 3, 5, and 7. Results. Treatment of rats with gentamicin resulted in renal damage evidenced by proteinuria, polyuria, and decreased creatinine clearance. The damage to the kidney proximal tubule was evident by (a) the histological analysis at light microscopy and (b) the augmentation in the urinary excretion of N-acetyl-β-d-glucosaminidase (NAG). Kidney ACE activity decreased while lung and serum ACE activity didn’t change until day 7. Lung ACE activity increased significantly on day 7. Kidney and serum ACE activity increased too. Blood pressure increased significantly on day 7. This corresponded well with the lung ACE activity increment. Conclusion. These data suggest that kidney ACE activity decreased significantly just one day after gentamicin administration and prior to kidney NAG decrease.

Possible Modulatory Role of Nitric Oxide in Lung Toxicity Induced in Rats by Chronic Administration of Bleomycin

Background: The present study was undertaken to evaluate whether stimulation or inhibition of nitric oxide (NO) synthesis could affect lung toxicity induced by chronic administration of bleomycin (BLM). L-arginine (ARG) and N^G-nitro-L-arginine methyl ester (L-NAME) were employed as NO precursor and NO synthesis inhibitor, respectively. Methods: BLM was administered intraperitoneally to male Wistar rats at a dose of 15 mg/kg, 3 times a week, for a total period of 4 weeks. ARG (500 mg/kg/day) and L-NAME (100 mg/kg/day) were given in drinking water, the treatments commenced with BLM and continued up to the end of the experiment. Appropriate controls were performed. Results: BLM treatment resulted in a pronounced fall in the average body weight of animals, together with a rise in the lung weight/body weight ratio. In the lung tissue, elevated levels of hydroxyproline (HP) and lipid peroxides (LP) as well as decreased activity of angiotensin converting enzyme (ACE) further evidenced the toxicity. Pulmonary level of NO end products, nitrite and nitrate, tended to rise but did not reach a significant level. Glutathione (GSH) content and GSH-peroxidase activity measured in the lung remained unaltered. In animals given concurrent treatment of BLM and ARG, a remarkable rise in the pulmonary level of nitrite and nitrate was observed. Average body weight was still decreased when compared with the untreated control group, but the decrease was significantly less than that observed in the BLM group. In addition, ARG decreased the extent of BLM-induced elevations of lung HP and LP levels. Meanwhile, ARG failed to significantly affect the BLM-evoked decrease in pulmonary ACE activity and increase in lung weight/body weight ratio. In animals given simultaneous treatment of BLM and L-NAME, noticeable reductions in the pulmonary levels of nitrite/nitrate and GSH were detected. BLM-induced decrease in body weight and increase in lung weight/body weight ratio were accentuated by L-NAME co-treatment. Furthermore, administration of L-NAME led to more profound elevations in lung HP and LP levels, without affecting the decrease in pulmonary ACE activity elicited by BLM. Conclusion: In principle, the present findings indicate that the lung toxicity exerted by chronic administration of BLM is alleviated by ARG, but exacerbated by L-NAME supplementation. This could indicate a possible protective role of NO.