Renal venous output of kinins in patients with hypertension and unilateral renal artery stenosis

Loss of prolyl carboxypeptidase in two-kidney, one-clip goldblatt hypertensive mice

It is well documented that angiotensin (Ang) II contributes to kidney disease progression. The protease prolyl carboxypeptidase (PRCP) is highly expressed in the kidney and may be renoprotective by degrading Ang II to Ang-(1-7). The aim of the study was to investigate whether renal PRCP protein expression and activity are altered in two-kidney, one-clip (2K1C) Goldblatt hypertensive mice. Left renal artery was constricted by using 0.12 mm silver clips. Blood pressure was measured using telemetry over the eleven weeks of study period and revealed an immediate increase in 2K1C animals during the first week of clip placement which was followed by a gradual decrease to baseline blood pressure. Similarly, urinary albumin excretion was significantly increased one week after 2K1C and returned to baseline levels during the following weeks. At 2 weeks and at the end of the study, renal pathologies were exacerbated in the 2K1C model as revealed by a significant increase in mesangial expansion and renal fibrosis. Renal PRCP expression and activity were significantly reduced in clipped kidneys. Immunofluorescence revealed the loss of renal tubular PRCP but not glomerular PRCP. In contrast, expression of prolyl endopeptidase, another enzyme capable of converting Ang II into Ang-(1-7), was not affected, while angiotensin converting enzyme was elevated in unclipped kidneys and renin was increased in clipped kidneys. Results suggest that PRCP is suppressed in 2K1C and that this downregulation may attenuate renoprotective effects via impaired Ang II degradation by PRCP.

Effect of upright tilting on kinins as compared to renin activity in the renal venous blood from patients with essential hypertension

The effect of tilting on the release of renal kallikrein as compared to renin was studied by the determination of kinin concentration and plasma renin activity (PRA) in the renal veins in supine position and after 15 min of 45 degrees upright tilting in 10 patients with essential hypertension. Kinin concentration decreased from 0.62 +/- 0.05 microgram/1 (mean +/- S.E.M.) in supine position to 0.51 +/- 0.05 after tilting (p less than 0.01), while PRA increased from 2.84 +/- 0.39 microgram/1/3 h tpo 4.87 +/- 0.66 (p less than 0.001). These results indicate that tilting diminishes the release of renal kallikrein. It is suggested that decreased intrarenal generation of kinins may be of importance for the reduction of diuresis and natriuresis induced by tilting.

The effect of the converting enzyme inhibitor SQ 20.881 on kinins, renin-angiotensin-aldosterone and catecholamines in relation to blood pressure in hypertensive patients

Nine sodium replete hypertensive patients with normal or high plasma renin activity (PRA) were given SQ 20.881, 1 mg/kg intravenously BP fell significantly within 20 min and reached its lowest level after 60 min. Blood kinins showed a minor but significant decrease after 60 and 105 min. Plasma angiotensin II was markedly reduced after 15 and 60 min. PRA was significantly increased after 15-105 min. Plasma aldosterone was reduced at 60 min in eight patients and slightly increased in one. Plasma noradrenaline increased after 15 min, whereas adrenaline decreased after 60 min. These results indicate that the reduction of BP following inhibition of converting enzyme by SQ 20.881, 1 mg/kg, is not related to reduced degradation of kinins but rather to decreased formation of angiotensin II. Angiotensin II appears to be of importance for the maintenance of BP in sodium replete hypertensive patients with normal or high PRA.

The renal kallikrein-kinin system in human and in experimental hypertension

The kallikrein-kinin system in the kidney is localized in the distal nephron, where it appears to be linked to processes that control water and electrolyte excretion. Some evidence exists that the effect of the renal kallikrein-kinin system is partially mediated by the release of prostaglandins. It has not yet been determined whether endogenous kinins affect the function of the nephron directly or indirectly by changes in renal blood flow distribution. Further, a number of studies in animals and humans indicates that kallikrein excretion is decreased in most types of hypertension, with the exception of hypertension caused by an excess of mineralocorticoids (where kallikrein is increased). In rats susceptible to the hypertensive effect of salt, kallikrein is conspicuously decreased. In renal diseases, urinary kallikrein excretion is also decreased. Finally, it still needs to be determined whether or not low kallikrein excretion is a pathogenetic factor in hypertension and renal diseases.