Increased plasma prorenin but not renin after bilateral ureteral ligation in dogs

Relationship between parathyroid hormone and renin-angiotensin-aldosterone system in hemodialysis patients with secondary hyperparathyroidism

INTRODUCTION

Hyperparathyroidism (HPT) is associated with mortality and cardiovascular disease (CVD) in dialysis patients. However, its mechanism is still unclear. It is suspected that parathyroid hormone (PTH) is associated with the renin-angiotensin-aldosterone system (RAAS) as a possible mechanism. Thus, we examined their hormonal interaction in hemodialysis patients with secondary HPT.

MATERIALS AND METHODS

Seventeen hemodialysis patients with HPT were included. All patients underwent total parathyroidectomy (PTx). Serum intact PTH (iPTH), calcium and phosphate levels, plasma renin activity (PRA), and plasma aldosterone levels (ALD) were measured pre- and post-PTx.

RESULTS

Pre-serum iPTH tended to be correlated with pre-PRA and were significantly correlated with pre-ALD (pre-PRA: r = 0.44, p = 0.07, pre-ALD: r = 0.49, p < 0.05). With the reduction in serum iPTH after PTx, PRA and ALD significantly decreased after PTx. Additionally, the change in serum iPTH tended to be correlated with the changes in PRA and ALD (PRA; r = 0.46, p = 0.05, ALD; r = 0.45, p = 0.06).

CONCLUSION

Our results suggest that PTH could be interrelated with RAAS in hemodialysis patients with secondary HPT.

Active renin, prorenin, and renin gene expression after reduced renal perfusion pressure in term ovine fetuses

We studied the pattern of plasma active renin concentration (ARC), prorenin concentration (PRC), renal renin concentration, and the renin mRNA levels in ovine fetuses subjected for 24 h to reduced renal perfusion pressure (RPP). The results obtained in five animals (133.8 +/- 1.4 days of gestation) in which RPP was reduced by 10 mmHg were compared with those in seven control fetuses (130.3 +/- 0. 8 days of gestation) without pressure reduction. Plasma samples were obtained before and at intervals of 24 h after initiating reduced RPP. The plasma ARC increased within 60 min of reduced RPP, reaching a maximum (13.0 +/- 4.7 vs. 115.7 +/- 23.8, P < 0.01) at 3 h. The ARC then declined toward control values. In contrast, plasma PRC did not increase consistently until 4 h into reduced RPP, with maximal levels at 24 h (8.2 +/- 2.4 vs. 87.7 +/- 21.9, P = 0.016). Within the kidney PRC, but not ARC, increased significantly, by 2.5-fold. Reduced RPP also increased renal renin mRNA levels (P = 0.004). We conclude that a chronic reduction in RPP in the near-term ovine fetus increases renal PRC and is associated with increased plasma prorenin levels. The data suggest that the conversion of prorenin to active renin is an important regulation point of the renin ANG system during development.

Circulating levels of active, total and inactive renin (prorenin), angiotensin I and angiotensinogen in carbon tetrachloride-treated rats

1. Plasma renin activity (PRA), plasma angiotensin I concentration (ANG I), plasma angiotensinogen concentration (PAC) and the plasma levels of active, total and inactive renin (prorenin) were measured in rats with carbon tetrachloride (CCl4)-induced acute renal failure. Rats were treated with a single oral dose of CCl4 (2.5 mL/kg) and killed 1, 2, 3 and 7 days later. 2. On days 1-3 PRA, ANG I and PAC decreased and increased on day 7. Active renin fell on days 2 and 3, total renin (trypsin treatment) augmented on day 1 and diminished on day 3, prorenin and per cent prorenin increased on days 1 and 2. Angiotensin I concentration paralleled PRA and PAC. The CCl4-induced decrease in PRA was secondary to the fall in active renin and in PAC. Total renin augmented as a consequence of the elevation of prorenin. Renal function, evaluated by serum urea, serum creatinine and creatinine clearance, decreased on days 1 and 2 when PRA was low and plasma prorenin was high. 3. These data do not support the involvement of the circulating active renin-angiotensin system (RAS) in the pathophysiology of acute renal failure induced by CCl4, however, increased prorenin levels were associated with the decrease in renal function.

Prorenin in diabetes mellitus

A rise in plasma prorenin often precedes the onset of vascular injury in patients with diabetes mellitus. Plasma prorenin measurements may be useful for predicting which patients will develop vascular injury and for monitoring the progression of the disease. A hypothesis is presented that accounts for these relationships and for the cosecretion of prorenin and renin into the circulation.

Lewis K. Dahl Memorial Lecture. The renin system and four lines fo hypertension research. Nephron heterogeneity, the calcium connection, the prorenin vasodilator limb, and plasma renin and heart attack

As the major regulator of arterial blood pressure and sodium balance, the renin axis supports normotension or hypertension via angiotensin-mediated vasoconstriction and angiotensin plus aldosterone-induced renal sodium retention. In this endocrine servo control, renal renin is released by hypotension or salt depletion; conversely, with hypertension or volume excess, plasma renin activity falls to zero. Accordingly, any renal renin secretion is abnormal in the face of arterial hypertension. Human hypertensive disorders comprise a spectrum of abnormal vasoconstriction-volume products (renin-sodium profiles). Excess plasma renin activity for the sodium balance is created by nephron heterogeneity in which a subpopulation of ischemic nephrons hypersecretes renin and retains sodium. This excess renin impairs adaptive natriuresis of neighboring normal nephrons. Research defining the pivotal role of vascular cytosolic calcium for transducing sodium or renin-mediated vasoconstriction explains the selective value of calcium antagonists for correcting the sodium-volume-mediated, and beta-blockers or angiotensin converting enzyme inhibitors for correcting renin-mediated, arteriolar vasoconstriction. The renin precursor prorenin appears to be physiologically active, causing selective vasodilation that offsets renin-mediated vasoconstriction. Overactivity of prorenin may be involved in the hyperperfusion vascular injuries of diabetes mellitus and toxemias. Prorenin underactivity may facilitate renin-mediated ischemic vascular injury. In essential hypertension, undue plasma renin activity is powerfully and independently associated with heart attack risk. Conversely, patients with low renin activity are protected from heart attack despite higher blood pressures and greater age. Also, renin or angiotensin administration consistently causes vascular injury in the heart, brain, and kidneys of animals. These data suggest new potentials for the prevention of cardiovascular sequelae (heart attack and stroke) by using explicit strategies to curtail plasma renin activity.

Acute hemodynamic and endocrinological effects of partial fetal bladder obstruction

The pathophysiology of fetal urinary obstruction has not been elucidated. Using a unique, reproducible and easily reversible animal preparation, we studied the acute hemodynamic and endocrinological responses to partial fetal bladder obstruction in 16 ovine fetuses at 115 days of gestation (term 147 days). After partial obstruction blood pressure and renal weight increased significantly for at least 72 hours. Renal blood flow trended upwards, particularly from 24 to 72 hours, although this change was not statistically significant. Plasma renin activity was significantly increased during the first 24 hours after obstruction but it returned to baseline thereafter. Plasma cortisol or catecholamine concentrations remained unchanged. The time course and pattern of hemodynamic changes in this fetal sheep preparation of partial urinary obstruction differ significantly from those reported in other preparations.