Robert E. Druilhet

Structure of neutral glycerides and phosphoglycerides of human kidney

Abstract 1. 1. Neutral lipids and phospholipids of human kidney have been isolated and the fatty acid composition of each determined. 2. 2. Triglycerides were fractionated into 7 bands by argentation chromatography. The major class (49%) was saturated, monoene, monoene. Stereospecific analysis revealed that both positions 1 and 2 contained an approximate ratio of 1:1 saturated to unsaturated fatty adds. 3. 3. Positional distribution of fatty acids in phosphatidylcholine, the major phospholipid component (27.2%), was determined by phospholipase A2 and pancreatic lipase hydrolysis. 4. 4. Overall results indicated similarities and differences when compared to kidney lipids of other mammalian species.

Renin as a risk factor for atherogenesis: Effects of hypercholesterolemia and two-kidney-one-clip hypertension in the rabbit

Four groups of New Zealand rabbits were used to study the effect of plasma renin activity (PRA) on atherogenesis. Control groups were fed normal rabbit chow (Group I) or chow supplemented with 0.25% cholesterol and 0.75% corn oil (Group II). The two-kidney--one-clip (2K-1C) hypertensive model was produced in 2 additional groups; Group III (normal diet) and Group IV (atherogenic diet). The latter 2 groups were subgrouped according to PRA levels. Each group was examined over a 7-month period. Group II became hyperlipidemic and developed extensive lipoidal vascular lesions. Mean arterial pressure remained normal throughout the experimental period; PRA fell below normal. Group III and Group IV rabbits developed sustained hypertension irrespective of circulating PRA. The atheromas of Group III were predominantly microscopic and fibromuscular; the extent of aortic and coronary artery involvement was independent of renin response. The most extensive and complicated atheromas were seen in the 2K-1C rabbits consuming the atherogenic diet (Group IV). The lesions were mostly lipoidal, although some were fibromuscular. These results demonstrated that cardiovascular lesions and atherogenesis were exacerbated in the 2K-1C rabbits on a high cholesterol diet; however, PRA was excluded as the cause.

Cortical and medullary lipids of normal and nephrosclerotic human kidney

Abstract 1. 1. Major lipid classes from cortical and medullary zones of normal and nephrosclerotic human kidneys have been isolated and the fatty acid composition of each determined. 2. 2. The nephrosclerotic tissue contained two times more total lipid than the normal kidney but, irrespective of kidney pathology, phospholipids were the major cortical lipids and neutral lipids were the predominant lipids in medullary zones. 3. 3. Human kidney contained large amounts of phosphatidylcholines, phosphatidylethanolamines and sphingomyelins and although these were slightly increased in the sclerotic kidney, anatomical differences in phospholipid content were not significant. 4. 4. Quantitative differences between the zones of normal kidney were found with triglycerides, diglycerides. free fatty acids and cholesterol; overall, the sclerotic tissue contained more triglycerides and small amounts of cholesterol esters with less significant regional differences. 5. 5. Palmitic, oleic and stearic acid were the major fatty acids of neutral lipids; these plus linoleic acid were prevalent in phospholipids.

Effect of human kidney lipids on human kidney renin activity.

Abstract The major lipids of human kidney tissue were isolated by solvent extraction, and the lipid composition was determined by thin-layer chromatographic techniques. The positional distribution of fatty acyl groups in ethanolamine and choline phosphatides was determined after enzymatic hydrolysis. Major phosphatides were assayed for plasmalogen content. Triglycerides were characterized by argentation chromatography. The fatty acyl composition of these lipids was also determined. The effect of intact triglycerides, phospholipids, 1- and 2-monoacyl phosphatides and ether lipids on renin activity in vitro was determined by incubations with 3-[U 14 C]valyl tetradecapeptide renin substrate. Kidney triglycerides, 1-monoacyl and 2-monoacyl phosphatidylethanolamines and phosphatidylcholines significantly inhibited renin activity. The renin-inhibitory effect of these lipids was comparable to inhibition by hog kidney phospholipid inhibitor. The intact phospholipids and cholesterol potentiated human kidney renin activity. Phosphatidylserines and synthetic glyceryl ether lipids have no significant effect. These results indicate that lipid-induced inhibition of human renin activity does not require the ethanolamine moiety, acyl group unsaturation, or the presence of a hydroxyl group at the 2-position. Additionally, no specific structure-activity relationships can describe lipid-renin interactions.

Renin as a risk factor for atherogenesis. Part 2. Effects of hypercholesterolemia and hyporeninemia in the rabbit.

Four groups of New Zealand rabbits were used to study the effect of suppressed plasma renin activity (PRA) on atherogenesis. Control groups were fed normal rabbit chow (Group I) or normal chow supplemented with 0.25% cholesterol--0.75% corn oil (Group III). Group II animals were fed normal chow and received periodic injections of 11-desoxycorticosterone (DOC)pivalate and 0.5% saline to drink, while Group IV animals were treated similarly except that they were also fed the atherogenic diet. Blood pressure and blood chemistry measurements were performed monthly over a 7-month period. The blood pressure was unaffected by either the diet or the DOC-saline treatment, however, the PRA was greatly reduced in the animals receiving DOC-saline (Groups II and IV). Similarly, plasma aldosterone was significantly (P less than 0.05) reduced in the DOC-saline-treated animals. No atheromata were observed in the animals consuming the regular diet, regardless of DOC-saline treatment. All of the animals fed the atherogenic diet showed extensive aortic atheromata. However, there was no difference in the lesion index between the animals with normal PRA levels (Group III) and those with suppressed PRA levels (Group IV). Likewise, microscopic evaluation of the aorta, coronary arteries, and renal arteries failed to show a consistent difference in the vascular involvement between animals of Groups III and IV. We therefore conclude that the suppression of PRA does not have a protective effect on atherogenesis in the cholesterol-fed normotensive rabbit.

Capoten-induced juxtaglomerular hyperplasia in rabbits.

The effects of the converting enzyme (CE) inhibitor, captopril, on blood pressure, plasma aldosterone, plasma renin activity (PRA), and kidney morphology were studied. Captopril, at a near maximum daily recommended human dose of approximately 5.0 mg/kg, was administered to rabbits over a period of six months. Mean arterial pressure, CE activity, and aldosterone levels were significantly reduced; PRA and renal renin activity were increased. Microscopic examination of the kidney showed marked hyperplasia of the juxtaglomerular apparatus in all of the treated animals.

Renin as a risk factor for atherogenesis. Part 3. Effects of hypercholesterolemia, hyporeninemia and one-kidney-one clip hypertension in the rabbit.

Abstract The purpose of this study was to test the hypothesis that plasma renin activity (PRA) is a risk factor for cardiovascular disease. Four groups of New Zealand rabbits were used to study the effects of PRA and hypertension on atherogenesis. Control groups were fed normal rabbit chow (Group I), or normal chow supplemented with 0.25% cholesterol (Group III) Group II animals were fed normal chow, had a clip placed around the left renal artery and were contralaterally nephrectomized (one-kidney-one-clip, 1K-1C). The renal arteries and kidneys of Group IV animals, which were fed a cholesterol diet, were manipulated similarly. Blood pressure and blood chemistry measurements were performed periodically over a 7-month period. The blood pressure was unaffected by either diet; however, PRA and aldosterone levels were greatly reduced in the 1 K-1 C groups (Groups II and IV). No atheroma were observed in any of the animals consuming the normal diet (Groups I and II) despite sharply elevated blood pressure in the Group II animals. Medial hypertrophy of small muscular arteries was observed in several Group II animals. All of the animals fed the atherogenic diet showed extensive aortic atheromata. There was, however, a significantly smaller lesion index for the normotensive cholesterol-fed animals (Group III) than those with increased blood pressure (Group IV). Likewise, microscopic evaluation of the aorta, coronary arteries, renal arteries, and kidneys mirrored this difference in the vascular involvement between the animals of Groups III and IV. We conclude that neither relatively high nor low PRA levels affect the development of atherosclerosis or other cardiovascular lesions. However, hypertension with a concomitantly high cholesterol diet acts synergistically in exacerbating atherogenesis.

Evidence against acetone-soluble renin inhibitors in normal human plasma.

SUMMARY The presence of acetone-soluble renin inhibitors in normal plasma bas been proposed to explain the variation of plasma renin reactivity (PRR) in samples from normotensive and hypertensive subjects. In our experience, acetone extraction decreased PRR in relation to unextracted control values, an observation which is not consistent with the circulating lipid-renin inhibitor hypothesis. Exposure to acetone at −40°C for 1 minute invariably denatured some endogenous angiotenslnogen. The PRR in extracted and unextracted plasma was positively correlated with the concentration of available angiotensinogen, r = 0.955 (p < 0.05), and r = 0.964 (p < 0.01), respectively, but the addition of exogenous substrate did not uniformly increase PRR in acetone-treated plasma above control values. These data argue against the use of acetone extraction to demonstrate the existence of circulating lipid-renin inhibitors. Acetone removed 14% to 25% of the normal plasma lipids and although the extract contained most of the major lipid classes, neutral lipids were the most abundant (73% by weight). The presence of acetone-soluble phospholipids appeared to increase angiotensln I formation in the partially purified renin-angiotensinogen system, but phospholipids interfered with the radiolmmunoassay and resulted in an overestimation of angiotensln I. Plasma neutral lipids decreased in vitro renin activity by 13% (p < 0.025) but this degree of inhibition suggests that lipid-renin interactions may have minimal in vivo physiological significance. In contrast to previous reports, we found the correlation between PRR and endogenous angiotensinogen in normotensive and hypertensive plasmas to be statistically significant (r = 0.643, p < 0.01). Inactivated human angiotensinogen was also shown to be an inhibitor of renin in vitro. This effect could have possibly influenced PRR values that were determined by others in the presence of inactivated angiotensinogen.

Action of a human plasma fraction on tetradecapeptide, angiotensin I and angiotensin II.

A protein fraction designated PF70 was isolated from human plasma and partially purified on Sephadex G-100. PF70 proteins, molecular weight 37, 000 to 41, 500, formed angiotensin I (AI) and angiotensin II (AII) from 14C-tetradecapeptide renin substrate (TDP) at 37 C. Hydrolysis was maximal at pH 6.9 but there was no change in the relative quantity of AI and AII formed at different pH values. Data indicate that AI was formed first and at a faster rate than AII, but typical converting enzyme activity was not detected. Radiolabeled AII was converted to Des-Asp1-angiotensin II (angiotensin III); [3H]AI was degraded to a single tritiated product, possibly the nonapeptide. These aspartyl hydrolase reactions were apparently inhibited by TDP and were not involved in AI or AII generation from TDP. It is concluded that these enzymic activities represent two or more enzymes that are associated with the renin-angiotensin system.

MULTIPLE KIDNEY RENINS ASSOCIATED WITH MALIGNANT HYPERTENSION

Publisher Summary This chapter discusses the occurrence of multiple renin forms or renin-like enzymes in the kidneys of a patient with malignant hypertension and compare the results with similar proteins isolated from cadaveric kidney tissue. The insignificant amount of renin activity observed with large-molecular-weight cadaveric tissue proteins and the relatively high renin activity seen with similar molecular weight fractions from the patients renal tissue suggest that the activity of these renin-like proteins were in part responsible for the unique clinical feature of the patient. The chapter illustrates renin-like activity of several molecular weight fractions isolated from the patients kidneys and cadaveric kidneys. Severe arterionephrosclerosis have induced the synthesis of these renin forms and precipitated polydypsia and malignant hypertension.