Influence of angiotensin 11, ouabain and hydrostatic pressure on inulin and electrolyte concentration of fluid perfusing pig carotid arteries

1. Angiotensin I1 was infused into isolated, perfused pig carotid arteries. The perfusate leaving the arteries was sampled into an Auto-analyzer system which continuously monitored its composition. Arterial pressure was recorded. 2. Low, subpressor doses of ygiotensin I1 raised the perfusate potassium concentration, whereas high doses, which produced contraction, lowered perfusate potassium and sodium concentrations. Inulin and chloride concentrations did not change. 3. The elevation of perfusate potassium with low angiotensin I1 dosage was appreciable compared with that caused by high doses of ouabain. 4. Neurotransmitter blockade did not alter the lowand high-dose angiotensin I1 effects. In other sequential dose studies, valine5-angiotensin I1 and isoleucine5-angiotensin I1 did not differ in their effects on perfusate composition or arterial contraction. 5. Mechanically increased hydrostatic pressure lowered perfusate sodium concentration, so that increased arterial pressure might have contributed to this aspect of high-dose angiotensin I1 effects. 6. These effects of angiotensin I1 might have physiological significance in relation to arterial smooth muscle and to electrolyte homeostasis.