1. The forearm blood flow responses to hypoxia obtained from ten subjects (ages 26–37 years) before and after propranolol showed no relation with either plasma osmolality or plasma concentrations of K + , Na + , Ca 2+ , P i and Cl − . The average oral dose of 3.3 mg of propanolol/kg body weight decreased the overall mean flow response to hypoxia by 42.2% ( P < 0.025). This reflects some β-adrenoceptor involvement. The residual vasodilatation observed after β-blockade by propranolol could be attributed to activation of cholinergic vasodilator fibres by hypoxic stress. 2. The mean heart rate during acute hypoxia before and after propranolol administration was 95 and 89 beats/min respectively. The residual tachycardia could be due to reduction of vagal tone during the hypoxic stress. 3. The response of arterial blood pressure to the hypoxic stress before and after propranolol administration, on the other hand, was found to be negligible in most subjects. This lack of response during emotional stress is in agreement with previous findings. In the present circumstances the possible increase in baroreceptor activity is probably masked by the general peripheral vasodilatation.

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.