1. The effects of an intravenous infusion of angiotensin on plasma electrolytes were examined in normal, adrenalectomized and nephrectomized groups of rabbits and in normal man. Rabbits were given 1 μg kg−1 min−1 and human subjects 0.008–0.030 μg kg−1 min−1 of angiotensin.
2. In normal rabbits, angiotensin increased arterial and venous plasma K within 2 min by 0.8 and 0.4 mmol l−1 respectively, some hyperkalaemia persisting for 30–60 min. After 60 min arterial plasma Na decreased by 3.8 mmol l−1 and Cl by 2.4 mmol l−1. Arterial blood pH increased 0.04 units after 15 min, and arterial plasma Mg and Ca rose slightly after 2 min. Pressor response was 20–28 mmHg.
3. In adrenalectomized and nephrectomized rabbits, arterial plasma K rose within 2 min by 2.6 and 3.8 mmol l−1 respectively. Arterial plasma Na fell after 60 min in both groups, and also after 2 min in nephrectomized animals. Venous plasma K and Na showed similar although less marked changes. Changes in plasma Mg, Ca and blood pH were not significant. Pressor response in both groups exceeded that in normal rabbits.
4. In man, a sustained rise of 0.2–0.3 mmol 1-1 occurred in arterial plasma K during angiotensin infusion. Arterial blood pH rose 0.01 units after 15 min. Pressor response was 12–15 mmHg.
5. It was concluded that plasma electrolyte levels may change during angiotensin administration in rabbits and man, and that these changes may influence interpretation of physiological actions of angiotensin.