Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.23.15 (renin)
 35,795 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Long considered a single clinical entity, essential hypertension is now recognized as a heterogeneous spectrum of pathophysiologic disturbances, based on extensive clinical, pharmacologic and biochemical evidence. Two distinctly different mechanisms for long-term vasoconstriction can be identified and quantified in the spectrum of patients with essential hypertension, although the causes of this group of disorders are still obscure. The first vasoconstrictor mechanism is renin-angiotensin mediated and involves an increase in vascular smooth muscle cytosolic free calcium mobilized from intracellular sites. The degree of activity of this mechanism can be assessed by plasma renin level and/or by the hypotensive response to circulating anti-renin-system drugs (such as CEI inhibitors and beta blockers). The second vasoconstrictor mechanism, on the other hand, is renin-independent. It appears to require antecedent renal sodium retention and to be related to abnormal membrane influx of calcium. A low plasma renin level identifies this kind of vasoconstriction, which is also characterized by a low serum ionized calcium. Low-renin vasoconstriction is correctable by sodium depletion or by calcium channel or alpha adrenergic blockade. Depending on the state of sodium balance, these two vasoconstrictor mechanisms contribute reciprocally to maintenance of arteriolar tone in models of experimental hypertension, normotensive and hypertensive people, and in the vasoconstriction of edematous states, such as congestive heart failure. One of the two mechanisms also sustains diastolic hypertension in the experimental and clinical forms of renovascular hypertension and primary aldosteronism. Thus, both experimentally and clinically, at the polar extremes of the range of plasma renin values, one of the two mechanisms predominates: it is possible that, in the medium range of renin values, both mechanisms contribute to vasoconstriction. In our proposed unifying, analytic model, arteriolar vasoconstriction is associated with increased intracellular calcium and decreased magnesium levels in vascular smooth muscle. In the vasoconstriction consequent to sodium-volume expansion, cytosolic calcium is increased by an increased membrane influx. In renin-mediated vasoconstriction, receptor-operated channels mobilize cytosolic calcium instead from intracellular stores. These interrelationships provide a basis for stratifying hypertensive patients pathophysiologically and for applying simpler, more specific, and more rational therapies. Thus, the array of modern pharmacologic agents can often be rationally directed at one or the other, or both, of these two vasoconstrictor mechanisms.
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PMID:Recognizing and treating two types of long-term vasoconstriction in hypertension. 305 33

Two different mechanisms for long-term vasoconstriction that sustain diastolic hypertension in the experimental and clinical forms of primary aldosteronism and renovascular hypertension can also be identified and quantified among patients with essential hypertension. The first is renin-independent, requires antecedent sodium retention, and appears related to abnormal membrane transport of calcium. This vasoconstriction is identified by low plasma renin and ionized calcium values and is correctable by sodium depletion or calcium channel or alpha-blockade. The second is renin-mediated but also involves an increase in cytosolic calcium. This mechanism is quantifiable by the plasma renin level and by the hypotensive response to an anti-renin-system drug (CEI inhibitor, saralasin, beta-blocker). At the very extremes of the range of plasma renin values encountered in hypertensive patients, one of the two mechanisms predominates, whereas in the medium range of renin values either or both mechanisms can be operative.
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PMID:Pathophysiology of diastolic hypertension. 307 77

To evaluate the hypothesis that sodium depletion produces a chronic increase in renal nerve activity, arterial and renal venous plasma norepinephrine (NE) concentrations were measured in conscious dogs subjected to various degrees of sodium depletion. After 9 days of sodium depletion (LS), there was a net loss of 69 +/- 10 meq sodium, and mean arterial pressure (MAP) was reduced from 94 +/- 5 to 88 +/- 4 mmHg. At this time plasma renin activity (PRA) was increased from a control level (sodium intake = 45 meq/day) of 0.34 +/- 0.08 to 1.47 +/- 0.26 ng angiotensin I (ANG I).ml-1.h-1 in association with an approximately sixfold increase in the PRA gradient across the kidneys. Subsequently, when captopril was infused during an additional 7 days of sodium deprivation [(LS + converting enzyme inhibitor CEI)], there was further sodium depletion (31 +/- 11 meq) and hypotension (MAP = 65 +/- 6 mmHg) and PRA and the renal PRA gradient increased even further. In marked contrast, there were no significant changes in either arterial plasma NE concentration (control = 102 +/- 5 pg/ml) or the renal arteriovenous gradient of plasma NE concentration during either LS or LS + CEI. These experiments show a distinct disparity between changes in the PRA and the plasma NE concentration gradient across the kidneys during LS and fail to support the contention that increased renal nerve activity is an important long-term adaptive response to sodium depletion.
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PMID:Disparity between renal venous norepinephrine and renin responses to sodium depletion. 328 92

1. The role of angiotensin as a modulator of proximal glomerulotubular (GT) balance was investigated in anaesthetized rats by examining the relationship between glomerular filtration rate (GFR) and absolute proximal reabsorption (APR) during removal of endogenous angiotensin II (AII) and III (AIII) with enalaprilat (CEI) and then during their subsequent replacement by intravenous infusions. 2. Enalaprilat lowered mean arterial blood pressure (MABP) and increased renal blood flow (RBF), GFR, urine flow rate and sodium excretion. Filtration fraction (FF) was not altered. Absolute proximal reabsorption, derived from fractional lithium clearance, increased by only 48% of the change expected for 'perfect' GT balance. 3. Angiotensin II replacement corrected MABP, GFR and plasma renin level, but reduced RBF and increased FF; APR was decreased and GT balance was restored. Urine flow and sodium excretion remained above control values with AII. 4. Replacement with AIII did not correct the hypotension but completely reversed the renal and renin responses to enalaprilat and restored GT balance without affecting FF. 5. It was concluded that the relation between proximal reabsorption and GFR is considerably modified by the intrarenal angiotensin concentration. The findings are best explained by a direct stimulation of proximal tubular sodium transport by angiotensin at the concentrations existing in anaesthetized rats.
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PMID:Effects of angiotensins II and III on glomerulotubular balance in rats. 331 34

Ten years of experience with three different converting enzyme inhibitors (CEI; teprotide, captopril and enalapril) in over 300 hypertensive patients reveals that CEI act largely to block renin-angiotensin mediated vasoconstriction. Thus, their effectiveness or lack of it is predicted by the baseline plasma renin measurement. Accordingly, responses to these pharmacological agents can be used to identify and quantify renin-mediated vasoconstriction in the spectrum of hypertensive diseases. The converse is also generally true. Patients failing to respond to CEI exhibit low renin values and their increased peripheral resistance appears related to other mechanisms, possibly involving a subtle increase in total body sodium. Thus, low renin states such as low-renin essential hypertension, primary aldosteronism, and anephric man exhibit little or no response to CEI. The relationship between the renin system activity and effectiveness of CEI reflects a specific interference with a particular pathogenic mechanism which is further supported by the fact that two other types of renin system inhibitors (beta-blockers and saralasin) are similarly effective or ineffective according to the operant renin profile also by studies in patients with congestive heart failure without hypertension in whom the same relationships can be demonstrated. Like hypertensives, heart failure patients exhibit a broad spectrum of renin activity values, and their pretreatment renin levels predict the responses to CEI. We have also found that plasma renin values in heart failure are dependent on sodium intake. When salt is administered, renin falls and patients then become unresponsive to CEI.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Converting enzyme inhibition to identify and treat renin-mediated or sodium-volume related forms of increased peripheral resistance in hypertension and in congestive heart failure. 608 35

In six inbred dogs with neonatally-induced coarctation hypertension, and in seven littermate controls, acute responses of proximal arterial pressure and plasma renin activity (PRA) to converting enzyme inhibitor (CEI; SQ 20,881, 0.5 mg/kg i.v.) were serially examined. Studies were performed at 2, 6, and 12 months post-aortic banding under sodium-replete and -deplete conditions. Both in normotensive controls and in coarcted dogs, depressor responses (pre- minus post-CEI values) were positively correlated, not only with initial (pre-CEI) PRA, but also independently with initial blood pressure. Although absolute depressor responses in coarcted dogs exceeded those of the control group, there were no significant group differences when, by analysis of covariance, depressor responses were adjusted for the physiologic influence of initial pressure. Similarly, depressor responses expressed as a percent of initial pressure were comparable in coarcted and control groups. Initial PRA and PRA response to CEI in coarcted dogs were also comparable to control dogs; the PRA response correlated with initial PRA in both groups. CEI did not significantly diminish the magnitude of blood-pressure difference between coarcted and control dogs. Thus, in neonatally-induced coarctation hypertension, under both sodium replete- and -deplete conditions: 1) acute depressor and PRA responses to CEI are modulated by the same factors that influence responses of normotensive controls; 2) larger absolute depressor responses to CEI appear to be a physiologic function of higher initial pressure; and 3) blood pressure excess over littermate controls is largely sustained by CEI-resistant factors, potentially including the known volume excess in coarcted dogs.
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PMID:Acute responses to arterial pressure and plasma renin activity to converting enzyme inhibition (SQ 20,881) in serially studied dogs with neonatally-induced coarctation hypertension. 617 44

Systemic, humoral and renal responses to isotonic volume expansion (VE, 1800ml in 3 hours) were assessed in normal subjects before and during captopril administration (CEI). Captopril, which otherwise induced a decrease in pre-saline mean arterial pressure (MAP) unmasked the volume-dependence of MAP since during captopril administration MAP increased linearly during volume expansion (+18.7 +/- 3.8% at the end of VE). In addition, captopril prevented the fall in plasma aldosterone produced by VE but did not modify the natriuretic response to saline. These results demonstrate that circulating angiotensin II is not an important determinant of the natriuretic response to volume expansion in normal man. However, a role for intrarenal renin cannot be excluded.
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PMID:Effect of captopril on the systemic and renal responses to acute isotonic volume expansion in normal man. 703 74

The antihypertensive, cardioprotective, and renoprotective effects of a nonpeptide angiotensin II antagonist (AIIA, CV-11974) and an angiotensin-converting enzyme inhibitor (CEI, captopril) were compared in Dahl salt-sensitive rats. Six-week-old male rats received a high-salt diet (4% NaCl) and were divided into control, CEI, and AIIA groups. The CEI group received captopril (15 mg/kg/day) and the AIIA group received CV-11974 (0.72 mg/kg/day), an active metabolite of the AIIA TCV-116, for 4 weeks by continuous subcutaneous infusion. After 4 weeks, systolic blood pressure (SBP) was significantly lower in the treatment groups than in the control group. The heart weight/body weight ratio and urinary protein excretion were reduced in the treatment groups, and renal damage (glomerular sclerosis score) was reduced by approximately 50%. CV-11974 and captopril were comparable in reducing BP, cardiac hypertrophy, and renal damage, suggesting that the renin-angiotensin (R-A) system is involved in elevating BP and promoting cardiovascular damage, despite suppression of the R-A system in this model. The antihypertensive effect of CEI may be due primarily to inhibition of the action of angiotensin II, while other effects, e.g., potentiation of the kinin system, may be less important.
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PMID:Comparative effects of an angiotensin-converting enzyme inhibitor and an angiotensin II antagonist in Dahl rats. 788 12

The effect of 24-hour unilateral ureteral obstruction (UUO) on the expression and regulation of the renin-angiotensin system (RAS) in rats and of pretreatment with lisinopril (5 mg/kg/day) or the AT1-R inhibitor, losartan, (10 mg/kg/day) on renal hemodynamics was evaluated. Both drugs improved the post-obstructed kidney (POK) renal hemodynamics, lowered MAP, and normalized eicosanoid excretion by the POK. Cortex and medulla POK:CK ratio of relative density R mRNA was approximately 3.5 for both. Sham, POK, and CK showed renin immunoreactivity and R mRNA exclusively in juxtaglomerular position. In addition, in POK renin was expressed in mesangial cells, along greater lengths of afferent arterioles and in dilated distal tubules and loops of Henle. In situ hybridization revealed that approximately 20% more glomeruli in POK than CK overexpressed R mRNA. Blood vessels of POK consistently showed greater ACE and Ao mRNA expression than CK. Overexpression of the genes coding for members of the RAS is possibly responsible for local Ang II production which, in view of the response to CEI and AT1-R inhibitors, is at least partly responsible for the severe hemodynamic changes in UUO.
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PMID:Regulation of renin-angiotensin system in unilateral ureteral obstruction. 839 17

The renin-angiotensin-aldosterone hormonal axis is the major long-term servocontrol for regulation of both arterial blood pressure and sodium balance. It supports normotension or hypertension via angiotensin vasoconstriction and angiotensin plus aldosterone-induced renal sodium retention. Normally, in the presence of hypertension or sodium-volume excess, plasma renin activity promptly falls to zero. Accordingly, any renal secretion of renin in the face of high blood pressure is abnormal. In established essential hypertension varying degrees of abnormal plasma renin activity operate to cause or sustain the hypertension; only very low plasma renin values reflect a normal renal response. Human hypertensive disorders comprise a spectrum of abnormal plasma renin-sodium volume products. High renin, intensely vasoconstricted, hypovolemic forms (e.g., malignant, renovascular) are one extreme of the spectrum; "wet"-volume-excess low-renin forms are the other extreme (e.g., primary aldosteronism, low-renin essential hypertension). These varying, but abnormal renin-sodium products are caused by a renal lesion in which a subpopulation of ischemic nephrons hypersecretes renin and retains sodium despite systemic hypertension and sodium excess. Thus, hypertensive patients cannot suppress their renin secretion normally. The hypertension from this renal lesion is correctable by agents that reduce renin secretion or block its effect (beta blockade, CEI, renin inhibition, or angiotensin II antagonism). None of these agents lower blood pressure after binephrectomy, verifying the renal origin of renin in the cardiovascular control system. In essential hypertension, the plasma renin level appears as a continuous variable associated with greater risk of ischemic injury.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The renin system and new understanding of the complications of hypertension and their treatment. 849 72


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