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SUMMARYMildly dehydrated conscious Merino ewes were infused with vasopressin (AVP) at 5 mu. min-' alone and simultaneously with the angiotensin II receptor blocker sarlala8-angiotensin II (saralasin) at 15 ug . min-m. AVP was slightly pressor and produced an increase in the calculated total peripheral resistance, and an increase in glomerular filtration rate, urine flow and electrolyte excretion, without a change in total renal plasma flow. These results indicate renal efferent arteriolar vasoconstriction as well as other non-renal vasoconstriction. Saralasin infusion checked the rise in total peripheral resistance (which continued to increase after saralasin withdrawal), but caused a marked increase in renal vascular resistance resulting in a decrease in renal plasma flow and to a lesser extent in glomerular filtration rate. These results suggest that saralasin was acting as an angiotensin II agonist in the kidney, but as an antagonist elsewhere. Deductions from previous experiments in the literature of the renal function of angiotensin II, based on its supposed inhibition by saralasin, may not be justified.

SUMMARYPlasma K+ was measured in Merino ewes during 50-90 min periods of hypotension induced by sodium nitroprusside, isoprenaline, verapamil or nifedipine. Doses were adjusted to produce falls in systemic blood pressure of approximately 20 mmHg. All of these drugs caused decreases in plasma K+ which could not be attributed to increased urinary excretion of K+. In all cases plasma renin activity increased during the hypotension. Plasma aldosterone concentration which was measured in some sodium nitroprusside experiments also increased during the hypotension. However, enhancement of the plasma renin activity and plasma aldosterone concentration responses by prior sodium depletion of the sheep by furosemide administration or suppression of the plasma renin activity and plasma aldosterone concentration responses by prior salt loading did not influence the magnitude of the hypotension-induced hypokalaemia.

SUMMARYGlomerular filtration rate (GFR) was assessed over a 2 h period by the clearance of inulin (Cin) and in the subsequent 2 h period by a single-injection technique using radiolabelled sodium iothalamate (Ci.0) or chromium-EDTA (CEDTA). Regression analysis yielded a significant correlation (P < 0.05) between the standard clearance technique and the single-injection method, with the relationship Ciot = -10-67 + 1.25Cin with a significant correlation coefficient of r = 0-71 (P < 0.02).