Serum angiotensin converting enzyme activity and plasma renin activity in experimental models of rats

Divergent profile between hypothalamic and plasmatic aminopeptidase activities in WKY and SHR. Influence of beta-adrenergic blockade

AIMS

Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) differ in their renin-angiotensin system function and sympathetic tone. The metabolism of angiotensins and vasopressin depends on the action of certain aminopeptidases whose activity may be influenced by the autonomic nervous system. Their regulation may differ between WKY and SHR in hypothalamus and plasma according to the sympathetic tone. We analyzed aminopeptidases responsible for the hydrolysis of certain angiotensins, vasopressin, cholecystokinin or enkephalins in hypothalamus and plasma of WKY and SHR in untreated controls rats and under beta-adrenoceptor blockade. Systolic blood pressure, food intake, water intake and diuresis were measured as parameters modulated by the autonomic nervous system and the above mentioned peptides.

MAIN METHODS

Glutamyl-, aspartyl-, cystinyl- and alanyl-aminopeptidase activities were analyzed fluorimetrically in plasma and hypothalamus of control and propranolol-treated (100mg/kg/day administered in drinking water for 1month) WKY and SHR, using arylamide derivatives as substrates.

KEY FINDINGS

An opposite response of aminopeptidases to propranolol treatment between plasma and hypothalamus was observed in either WKY and SHR. Furthermore, the behavior of aminopeptidases was inversed between WKY and SHR either in hypothalamus and plasma: while the activity increased in hypothalamus and decreased in plasma of WKY, it decreased in hypothalamus and increased in plasma of SHR.

SIGNIFICANCE

These results revealed an inverse response of aminopeptidases between hypothalamus and plasma and also an opposite behavior of these enzymes between WKY and SHR in hypothalamus and plasma. These observations support the involvement of the sympathetic system in the modulation of aminopeptidase activities.

Combination of β Adrenergic Receptor Block and Renin-Angiotensin System Inhibition Diminished the Angiotensin II-Induced Vasoconstriction and Increased Bradykinin-Induced Vasodilation in Hypertension

In hypertension, the combination therapy is frequently used to obtain a better therapeutic effect and reduce adverse effects. One effective combination is with inhibitors and β-blockers of renin–angiotensin system. Although the mechanisms of action of each drug are already known, the antihypertensive mechanism is more complex and therefore the combined treatment mechanism is unclear. Specifically, the effect of the treatments of angiotensin-converting enzyme inhibitor or AT₁ receptor antagonist with β-blocker on the angiotensin II and bradykinin reactivity has not been studied. For this reason, we evaluated the interaction between propranolol and captopril or losartan on vascular reactivity to bradykinin and angiotensin II in spontaneously hypertensive rat. We constructed concentration–response curves to angiotensin II and bradykinin after treatment of SHR with propranolol–captopril or propranolol–losartan by using rat aortic rings. While losartan or captopril with propranolol potentiated bradykinin-induced vasodilation effect, the propranolol–losartan interaction decreased the angiotensin II-induced vasoconstriction. In addition, the combinations did not reduce the heart rate significantly. These results suggest that the combined therapy decreased blood pressure to normotensive values and showed less effect for angiotensin II and greater effect for bradykinin than monotherapy which could contribute in the antihypertensive effect.

Angiotensin converting enzyme activity and nitric oxide level in serum patients with dehydration

Angiotensin converting enzyme (ACE) and nitric oxide (NO) have been suggested to be involved in the regulation of fluid homeostasis. In the present investigation, ACE activity and NO levels were determined in serum of 20 patients (10 men and 10 women) with dehydration caused by gastroenterocolitis and 20 healthy individuals (10 men and 10 women). Serum and tissue ACE activity was determined by spectrophotometric method using hippuryl-l-histidyl-l-leucine (Hip-His-Leu) as a substrate. NO synthesis was determined by measuring the products of NO, nitrite and nitrate. The concentration of nitrites was determined by classic colorimetric method using Griess reagent. Nitrate concentration was determined indirectly by their reduction with elementary zinc into nitrite. Results have shown that serum ACE activity in patients with dehydration (36,46+/-2,74 U/L) is statistically higher then in healthy individuals (28,71+/-1,77 U/L, p<0,05). The average level of nitrites/nitrates in serum of patients with dehydration (30,57+/-1,05 microM; mean +/- SEM) is also statistically higher then in healthy individuals (12,44+/-0,60 microM, p<0,0001). There was no correlation between ACE activity and NO production. The results indicate that ACE and NO may participate in the regulation of the alteration in blood flow and in the regulation of the water balance in patients with dehydration.

Angiotensin converting enzyme gene polymorphisms do not predict the course of idiopathic nephrotic syndrome in Swiss children

AIM

Contradictory reports exist about a correlation of angiotensin I converting enzyme (ACE) gene polymorphisms to the outcome of idiopathic nephrotic syndrome (INS) in children. We investigated the frequency of ACE polymorphisms and their impact on the clinical course of INS in children in a Swiss hospital.

METHODS

The ACE gene polymorphism (I, insertion; D, deletion) was assessed in 32 children - 22 with steroid-sensitive INS and 10 with steroid-resistant INS - with a median age at onset of INS of 2.9 years (range 1.1-15.0). Polymerase chain reaction amplification was performed on genomic DNA isolated from blood leucocytes. Results were correlated to clinical course and renal morphology.

RESULTS

The ACE genotype was I/I, I/D and D/D in two, 12 and eight patients, respectively, with steroid-sensitive INS, and in one, eight and one patient, respectively, with steroid resistance. Renal morphology, available in 25 patients showed minimal change glomerulopathy in 17 patients (14 steroid-sensitive; three steroid-resistant) and focal segmental glomerulosclerosis in eight (one steroid-sensitive; seven steroid-resistant). There was no significant correlation between ACE genotype and steroid responsiveness, histology or outcome. ACE genotype was I/I, I/D and D/D in none, 12 and five patients, respectively, with minimal change glomerulopathy, and in one, five and two patients, respectively, with focal segmental glomerulosclerosis. Six patients with steroid-resistant nephrotic syndrome went into end stage renal disease; ACE genotype was I/I in one and I/D in five, but none were D/D.

CONCLUSION

In contrast to previous reports, ACE gene polymorphism is irrelevant for clinical outcome, steroid responsiveness or morphology in Swiss children with INS.

Renal dysfunction as a consequence of acute liver damage by bile duct ligation in cirrhotic rats

Renal failure is a common complication in patients with alcohol-induced cirrhosis who undergo a superimposed severe alcoholic hepatitis.

AIM

Our aim was to evaluate renal dysfunction established as a consequence of acute liver damage (ALD) induced by bile duct ligation (BDL) in cirrhotic rats. Hepatic and renal functional assays were performed.

RESULTS

Hyperbilirubinemia and increased alanine aminotransferase and aspartate aminotransferase (p<0.05) in rats with BDL were observed since the first day of bile obstruction in cirrhotic rats. Urinary volume and urinary sodium concentration showed a significant reduction (p<0.05) on days 3 and 5 after BDL. Plasma renin activity, plasma renin concentration, serum creatinine, and BUN values increased (p<0.05) from day 1 to day 7 after BDL. Glomerular filtration rate was substantially decreased from day 1 to day 7. Histological changes became apparent since day 3 after BDL in which glomeruli with mesangial hypercellularity took place in the absence of tubular necrosis; with portal inflammation and proliferation of biliar conduits. Results of the present work demonstrate that ALD induced by BDL in cirrhotic rats produces changes in renal function. In conclusion, this experimental model demonstrates that an ALD of variable etiology, either surgical or induced by CCl(4), can cause important damage that eventually results in renal function deterioration. This experimental model may be suitable, to study the physiopathology of this syndrome, as well as for the evaluation of different pharmacological therapies.

The heterogeneous and delayed course of blood pressure normalization in hypertensive patients after bilateral nephrectomy with and without subsequent renal transplantation

BACKGROUND

Controversy exists about the time course of blood pressure normalization following bilateral nephrectomy. We sought to evaluate the time course of blood pressure normalization following bilateral nephrectomy and after subsequent kidney transplantation.

METHODS AND RESULTS

Clinical data from 14 hypertensive patients were retrospectively assessed. Baseline blood pressure was 175 +/- 33/109 +/- 9 mmHg. Ten patients firstly underwent unilateral nephrectomy, which resulted in a slight increase of blood pressure (185 +/- 22/110 +/- 5 mmHg). One month following bilateral nephrectomy, blood pressure was 167 +/- 23/104 +/- 17 mmHg, at 3 months 159 +/- 42/104 +/- 25 mmHg, and at 6 months 149 +/- 41/96 +/- 30 mmHg. Antihypertensive medication was necessary in 9/14 patients at a 2 year follow-up. Eight patients remained anephric (group I), 6 patients had subsequent kidney transplantation (group II). In group I, blood pressure was 159 +/- 42/93 +/- 17 mmHg and 129 +/- 34/75 +/- 14 mmHg at 3 and 6 months, respectively (p< 0.05 vs. baseline). In group II, blood pressure decreased from 188 +/- 42/ 128 +/- 46 mmHg to 167 +/- 48/113 +/- 32 mmHg at 3 months, but increased after transplantation to 186 +/- 39/118 +/- 33 mmHg. Antihypertensive medication was still necessary in 5 transplanted patients (83%) and in 3 anephric patients (38%).

CONCLUSION

Adaptation of the blood pressure response following bilateral nephrectomy is a time requiring process, and long-term antihypertensive medication may still be necessary.

Differential effect of CCl4 on renal function in cirrhotic and non-cirrhotic rats

The pathogenesis of renal function alteration associated with liver disease remains to be elucidated. Although different experimental animal models have been utilized in order to explain such pathophysiological state, none of them have completely explained the mechanisms involved. In this study we performed differential hemodynamic, hepatic and renal function alteration studies after induction of acute liver damage via intragastric administration of a single dose of CCl4 to cirrhotic and non-cirrhotic rats. Cirrhotic rats with acute liver damage exhibited a significant decrease in mean arterial pressure followed by a decreased glomerular filtration rate, urinary sodium concentration and an induction of plasma renin concentration and activity. At the same time, a significant association between oliguria and mortality was observed. The renal histopathological studies revealed glomeruli with mesangial hypercellularity and thickening of capillary wall, but not tubular epithelial injury. All these alterations were not detected in the control group, i.e. by non-cirrhotic rats with acute liver damage. This study suggests that the effect of CCl4 on kidney structure and function depends on the functional state of the liver. Since this experimental model of acute liver damage in cirrhotic rats presents hemodynamics and renal function alterations similar to those observed in the hepatorenal syndrome in man, it could be utilized to study the pathogenesis of renal function alterations associated with liver damage.

Biochemical bone markers, bone mineral content, and bone mineral density in rats with experimental nephrotic syndrome

The human nephrotic syndrome (NS) is accompanied by important alterations of mineral and bone metabolism. The purpose of the present study was to examine bone metabolism in rats with experimental NS and normal creatinine clearance, and to evaluate the reversibility of this alteration. NS was induced by three injections of puromycin aminonucleoside (PAN) on days 0, 21, and 35 (10, 5, and 5 mg/100 g body weight, respectively). The biochemical markers of bone formation (osteocalcin and alkaline phosphatase) and bone resorption (hydroxyproline and pyridinoline), bone mineral content (BMC), and bone mineral density (BMD), determined by dual-energy x-ray absorptiometry (DEXA), were studied on days 0, 7, 14, 28, 42, 56, 84, and 112. Proteinuria was present throughout the study. Hypoproteinemia was seen on days 7, 28, 42, and 56, returning to control values on days 84 and 112. In serum, osteocalcin (OC) concentration increased (p < 0.001), and alkaline phosphatase (ALP) decreased (p = 0.002). In urine, hydroxyproline increased (p < 0.001), but urinary pyridinoline was not different from the control group throughout the study. Increased serum parathyroid hormone concentration and decreased levels of 25-hydroxy and 1,25-dihydroxyvitamin D were found from day 7. During the intense proteinuria, bone resorption predominates and decreased BMC and BMD ensues in PAN-nephrotic rats. PAN-nephrotic rats showed low BMC and BMD compared to control group (p < 0.001). At the end of the study, when proteinuria persisted but total serum protein returned to control values, the biochemical bone markers, BMC, and BMD returned to normal. In conclusion, PAN-nephrotic rats had reversible bone alterations that were related to the magnitude of proteinuria and the concentration of total serum protein.

Plasma angiotensin in binephrectomised mice

Plasma renin-angiotensin parameters were measured before and 24h after binephrectomy (BNx) in male Swiss (Ren-1, Ren-2) and BALB/c (Ren-1) female mice (representing the extremes of differences in tissue renin expression), together with in vivo inhibition of residual renin. Plasma Ang II increased from 18.9 +/- 7.3 to 48.1 +/- 16.9 pg/ml after BNx in conscious Swiss mice (+/- sd, p < 0.001, n = 11&12), renin activity (PRA) increased 2.76 times, angiotensinogen (aogen) increased 4.57 times and renin concentration (PRC) fell by 65%. In BALB/c, Ang II+Ang III decreased slightly (56.6 +/- 11 to 37.7 +/- 14.7, p < 0.05, n = 5&6), PRA was unchanged, aogen increased 12 times and PRC fell by 93%. Plasma ACE decreased by 26% and 28% respectively. Aogen did not increase further when post BNx plasma renin was inhibited with antirenin in vivo during 20h. Thus plasma angiotensin is maintained or considerably increased following BNx in mice and the change is consistent with first-order kinetics with respect to renin and aogen in the circulation. Whether the strain carries one or two renin genes, high renal and extrarenal renin production combined with a low plasma aogen phenotype yields resting angiotensin levels similar to other mammals. A kinetic regulation of aogen levels is proposed in mice wherein Ang II production is limited by low substrate concentration thereby ensuring normotension in the face of abundant extrarenal renin secretion.

Effect of dietary antioxidants on puromycin aminonucleoside nephrotic syndrome

Several studies indicate the pathophysiological importance of reactive oxygen species in rats with nephrotic syndrome induced by puromycin aminonucleoside, an experimental model of the human minimal change disease. The role of reactive oxygen species in these rats was further evaluated, examining the effect of dietary deficiency and supplementation of antioxidants (vitamin E and selenium) on biochemical and renal ultrastructural alterations induced by puromycin aminonucleoside. Male Wistar rats, weaned at 3 weeks, were placed on diets normal, deficient or supplemented in vitamin E and selenium for 4 weeks. At the end of this period, rats were divided in two groups: control (sacrificed without any further treatment) and nephrotic (injected with puromycin aminonucleoside and sacrificed 7 and 22 days later). In control rats, the dietary deficiency or supplementation of antioxidants resulted in no significative differences in renal function, proteinuria or kidney ultrastructure. However, kidney lipoperoxidation, kidney glutathione peroxidase activity and circulating levels of vitamin E changed according to the amount of antioxidants in the diet. Seven days after the injection of puromycin aminonucleoside, rats fed normal, deficient or supplemented diets, developed nephrotic syndrome. However, proteinuria, hypoproteinemia, renal dysfunction and ultrastructural alterations were higher in rats fed a deficient diet. In contrast, proteinuria and kidney ultrastructural alterations were lower in rats fed a supplemented diet. Kidney lipoperoxidation and glutathione peroxidase activity increased on day 7 in rats fed a normal or a deficient diet, but not in rats fed a supplemented diet. This study shows that nephrotic syndrome induced by puromycin aminonucleoside in rats is modified by dietary antioxidants (vitamin E and selenium). Dietary supplementation ameliorates it and dietary deficiency exacerbates it.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin I converting enzyme activity in adriamycin induced nephrosis in rats

Activity of the dipeptidyl hydrolase angiotensin converting enzyme (ACE) has been observed to be altered by treatment with adriamycin (ADR). We used an animal model of ADR nephrotoxicity to study the effects on ACE in serum, urine and tissues on days 5, 10, 15, 20, 25 and 30 after ADR administration. Both glomerular and tubular injury occurred as evidenced by heavy proteinuria, albuminuria and increased urine N-acetyl glucosaminidase (NAG) excretion. Serum ACE was significantly elevated on days 20, 25 and 30. Of great interest was the excretion of ACE in urine of treated rats which ran parallel with the total protein excretion above the barely detectable levels found in controls. ACE activity increased in kidney, adrenal gland and liver on days 15, 20, 25 and 30. Heart and brain ACE levels increased on days 25 and 30. Increased ACE activity in aorta and lungs occurred on days 20, 25 and 30. ACE activity decreased in kidney, aorta, heart and brain on days 5 and 10. These observations strongly suggest a contribution of various tissues to elevate the serum ACE level. Urinary ACE may be of potential use as an index for renal glomerular and tubular damage.

Effect of a short-term captopril treatment on serum and tissue angiotensin I-converting enzyme activity from four mammalian species. Differences using diamide in the in vitro assay

1. Angiotensin I-converting enzyme (ACE) activity was determined in serum and nine tissues from control and captopril-treated rats, mice, guinea pigs and rabbits. 2. ACE activity was determined with and without sample pretreatment with diamide (total and basal activity, respectively). 3. A very different pattern of response to captopril was observed among the different species. 4. There was no relationship between serum ACE activity and the response to captopril. 5. There were important differences in the determinations of total or basal ACE activities. 6. Endogenous ACE inhibitors were found in some tissues from mouse and rabbit.

Electrophoretic analysis of serum and urinary proteins in rats with aminonucleoside-induced nephrotic syndrome

Albumin; and alpha 1-, alpha 2-, beta-, and gamma-globulins were estimated by cellulose acetate electrophoresis in the serum and urine from rats with nephrotic syndrome (NS), 2, 4, 6, 8, 10, 12, 16, 20, and 30 days after a single injection of puromycin aminonucleoside (PAN). It was found that: (a) total serum protein level decreased on days 4-16, and total urine protein excretion rose on days 6-16; (b) serum albumin level fell on days 4-16, and urine albumin excretion increased on days 6-16; (c) serum alpha 1-globulin level rose on days 8-30, and urine alpha 1-globulin excretion increased on days 8-16; (d) serum alpha 2-globulin level remained essentially unchanged, and urine alpha 2-globulin excretion rose on days 4-10; (e) serum beta-globulin level decreased on days 4-20, and urine beta-globulin excretion increased on days 6-16, (f) serum gamma-globulin level diminished on days 6, 8, and 12, and urine gamma-globulin excretion rose on days 6-10. All serum protein fractions were excreted in the urine of nephrotic rats; these findings suggest that proteinuria is nonselective. The differences observed in the serum protein profiles, even when all protein fractions were lost in the urine, suggest an independent regulation of each protein fraction in PAN-nephrotic rats. In addition, the electrophoretic profile of serum proteins in PAN-nephrotic rats is different from previously reported patterns in human nephrosis and in rats with an acute-phase response.

Angiotensin I-converting enzyme activity in rats with carbon tetrachloride-induced acute renal failure

The angiotensin I-converting enzyme (ACE) activity was measured in urine, serum, and tissues from rats with carbon tetrachloride (CCl4)-induced acute renal failure on days 1, 2, 3, and 7 after CCl4 administration. Serum ACE increased on days 1 to 3. Heart, lung, small intestine, brain, and testis ACE decreased, whereas kidney and liver ACE remained unchanged. Urine ACE activity increased from day 1 to day 3. Our data suggest that the increase in serum ACE may be secondary to the ACE release from the damaged tissues, and that the urine ACE increase may be due to the kidney proximal tubule damage. This work supports the contention that an increase in urine ACE may be an indicator of damage to the proximal tubule.

Captopril magnifies the increase in angiotensin I-converting enzyme activity in rats with aminonucleoside nephrosis

1. Serum, tissue and urine angiotensin I-converting enzyme (ACE) activity was estimated in the following groups of rats: saline-injected rats (controls); captopril-treated (CAP) control animals (CONTROL-CAP); puromycin aminonucleoside (PAN)-induced nephrotic syndrome (NS); and CAP-treated animals with NS (NS-CAP). 2. Serum ACE activity increased in the CONTROL-CAP, NS, and NS-CAP groups. The increase in the NS-CAP group was significantly higher compared with the NS or CONTROL-CAP groups. 3. In the CONTROL-CAP group, tissue ACE decreased in brain, heart and adrenal glands, and remained unchanged in the lung, testis, kidney, small intestine and liver. In the NS group, tissue ACE activity increased in the lung and testis, decreased in the brain and heart, and remained unchanged in the small intestine, adrenal glands, kidney and liver. Tissue ACE activity increased significantly in the NS-CAP group compared with the other groups. This increase in tissue ACE may contribute to an increase in the serum ACE activity in the NS-CAP group compared with the NS group. 4. Urine ACE activity increased in the NS and NS-CAP groups, although the rise in the NS-CAP group was significantly higher. The urine ACE correlated significantly with the circulating levels of this enzyme in the NS and NS-CAP groups. The loss of ACE in the urine in the presence of an increased serum ACE activity indicates that the biosynthesis of tissue ACE and its release into the bloodstream must be elevated.

Activity of serum enzymes in puromycin aminonucleoside-induced nephrotic syndrome

Total serum protein, serum albumin, total urine protein excretion, and the serum activity of several enzymes--aldolase (ALS), cholinesterase (CHS), leucine aminopeptidase (LAP), isocitrate dehydrogenase (ICD), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (HBD), creatine kinase (CK), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT)--were estimated in rats with nephrotic syndrome (NS) at 2, 4, 6, 8, 10, 12, 16, 20, and 30 days after a single injection of puromycin aminonucleoside (PAN). It was found that: (a) total serum protein and serum albumin diminished on day 4 and returned to control values on days 20 and 30, respectively; (b) total urine protein excretion rose on day 4, reached a peak value on day 8, and then fell substantially but still remained higher than control values on day 30; (c) ALS and CHS activities increased; (d) LAP, ICD, and AST activities showed a biphasic pattern, first increasing and then decreasing; (e) ALT, LDH, HBD, CK, and ALP activities decreased; and (f) GGT activity remained unchanged. The differences in the profiles of the enzyme activities suggest their independent regulation in experimental NS induced by PAN.

Angiotensin I-converting enzyme activity in puromycin aminonucleoside-nephrotic syndrome

Puromycin aminonucleoside (PAN)-nephrotic rats have high serum angiotensin I-converting enzyme (ACE) activity. We studied ACE activity in serum, urine, and tissues from PAN-nephrotic rats on days 2, 6, 11, and 16 after PAN injection. Proteinuria and hypoproteinemia were evident on days 6 and 11. Though significantly decreased, proteinuria was still evident on day 16. Serum ACE activity increased on days 2, 6, and 11. Urinary ACE activity became evident on days 6, 11, and 16 and correlated positively with proteinuria, suggesting that the source of urine ACE is the blood serum. ACE activity increased in testis on days 2 and 6, in lungs and aorta on days 6 and 11, in adrenal glands and small intestine on day 11, and in kidney on days 11 and 16. Heart ACE activity decreased on days 2 and 6, and increased on day 16; brain ACE activity decreased on day 6 and increased on day 11. These data implicate that changes in tissue ACE content may contribute to elevate serum ACE in PAN-nephrotic rats.