1. Angiotensin II 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 angiotensin II 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 II dosage was appreciable compared with that caused by high doses of ouabain.
4. Neurotransmitter blockade did not alter the low- and high-dose angiotensin II effects. In other sequential dose studies, valine5-angiotensin II and isoleucine5-angiotensin II 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 II effects.
6. These effects of angiotensin II might have physiological significance in relation to arterial smooth muscle and to electrolyte homeostasis.
