Antidiuresis Produced by Injection of Renin into the Third Cerebral Ventricle of the Dog

Abstract

The purpose of this study was to determine whether centrally administered renin stimulated vasopressin secretion. Vasopressin was not measured directly, but, instead, changes in urinary water excretion in anesthesized dogs undergoing a water excretion in anesthetized dogs undergoing a water diuresis were used as an index of changes in vasopressin secretion. Intraventricular injection of hog renin in a dose of 0.1 Goldblatt unit produced a marked decrease in urine flow which was associated with a decrease in free water clearance and an increase in urinary osmolatiy with no change in osmolar clearance. Sodium excretion increased significantly but there was no change in potassium excretion. These effects, which closely resemble those resulting from an increase in vasopressin secretion, were prevented by hypophysectomy. The antidiuretic effect clearly resulted from an action of renin in the central nervous system since renin had no effect on urine flow or osmolality when administered intravenously. Intraventricular administration of saralasin acetate, a specific antagonist of angiotensin II, completely blocked the effects of intraventricular renin indicating that these effects were mediated via the formation of angiotensin II. The data therefore indicate that there is an interaction between injected renin, brain angiotensinogen, and converting enzyme resulting in the formation of angiotensin II which stimulates the secretion of vasopressin. Additional studies are required to determine whether the brain renin-angiotensin system plays a physiological role in the regulation of a vasopressin secretion.

Endogenous Angiotensin Stimulation of Vasopressin in the Newborn Lamb

“…The mean basal plasma AVP level in the nephrectomized lambs (6.6 +3. 4 ,uU/ml) was higher than in the control lambs; it is unclear whether this represents increased secretion or decreased clearance of AVP. The water and salt diuresis (Table VI) There was no correlation between the fall in blood pressure and the AVP responses (Tables II, IV).…”

“…The mean base-line plasma AVP concentration, 2.1±0. 4 ,U/ml, increased to 10.8±2.0 at 35 min, and 13.8±2.1 ,uU/ml at 65 min after infusion, and fell to 8.7±1.5 AU/ ml at 125 min after infusion. These mean values at 35-125 min were significantly higher than the baseline concentration (each P < 0.01).…”

“…Plasma AVP and aldosterone concentrations increased from respective mean values of 2.1+0. 4 ,uU/ml and 12.8±2.5 ng/dl to 9.8±2.0 ,uU/ml (P < 0.01) and 23.0±7.7 ng/dl (P < 0.05) at 35 min and 13.8±2.1 ,uU/ml and 23.0 +4. 4 ng/dl at 65 min after furosemide (each P < 0.01).…”

“…4 ,uU/ml and 12.8±2.5 ng/dl to 9.8±2.0 ,uU/ml (P < 0.01) and 23.0±7.7 ng/dl (P < 0.05) at 35 min and 13.8±2.1 ,uU/ml and 23.0 +4. 4 ng/dl at 65 min after furosemide (each P < 0.01). There was an insignificant AVP response in the 10 lambs treated with angiotensin inhibitor: from a mean base line of 4.7±0.9 to 8.3+±2.0 ,uU/ml at 35 min, and 7.4 ±2.0 ,.U/ml at 65 min after furosemide.…”

“…INTRODUCTION Intravenous administration of pressor amounts of angiotensin II in the conscious dog (1,2) or intracarotid infusion in the anesthetized dog (3) provokes an increase in plasma vasopressin (AVP)' concentration. Ventriculo-cistemal applications of renin or angiotensin also can increase plasma AVP (2)(3)(4)(5). Recently, it has been shown that centrally administered renin evokes marked dipsogenic and pressor effects mediated via formation of angiotensin II within the central nervous system (6,7).…”