1. Renal function and morphology were studied before and after 60 min of renal ischaemia and contralateral nephrectomy in five groups of rabbits. The animals were pretreated with superoxide dismutase, catalase, allopurinol or mannitol. One group was not pretreated and served as a control. 2. A moderate transient increase in serum creatinine concentration was observed in the control rabbits, while a significantly less pronounced increase was noted after pretreatment with superoxide dismutase, catalase and mannitol. 3. Pretreatment with allopurinol did not significantly reduce the postoperative increase in serum creatinine and sodium excretion, but the urine osmolality returned to normal more rapidly than in the control group. 4. The appearance under the light microscope of kidney tissue taken from surviving rabbits was found to be normal irrespective of pretreatment. Severe tubular necrosis was observed in the kidneys from rabbits that died during the observation period.

1. The intrarenal erythrocyte distribution, total renal blood flow and renal vascular resistance were studied before and during recirculation after 60 min of warm ischaemia in three groups of rabbits. One group was pretreated with superoxide dismutase, another with catalase and the third group was not pretreated at all. 2. In non-pretreated ischaemic kidneys there was a significant trapping of labelled erythrocytes in the outer stripe of the medulla. This trapping was not seen in non-ischaemic control kidneys and was completely prevented by pretreatment with either superoxide dismutase or catalase. 3. In non-pretreated ischaemic kidneys there was a transient increase in total renal blood flow during the first 5 min of recirculation, after which it returned to preischaemic values. After pretreatment with catalase the postischaemic increase in blood flow was more pronounced but again the blood flow returned to preischaemic values within 30 min. Pretreatment with superoxide dismutase resulted in a rapid postischaemic increase in blood flow which remained high throughout the 30 min period studied. 4. The renal vascular resistance decreased initially during recirculation after ischaemia in both pretreated and non-pretreated kidneys. In the latter it returned to pre-ischaemic values within 10 min whereas a slower increase was observed after catalase pretreatment. After pretreatment with superoxide dismutase the resistance remained low during the 30 min recorded.

1. Stimulation with noise (100 dBA) for 10 min caused a significant increase in diastolic and mean arterial pressure in normotensive subjects with and without a positive family history of hypertension. 2. The blood pressure response in the group with a positive family history of hypertension was due to a significant increase in total peripheral resistance (9%, P < 0.05); no such change was seen in the group without heredity for hypertension. 3. Systolic blood pressure, heart rate, stroke volume and cardiac output did not change significantly during exposure to noise. 4. There was no difference between the groups in mean intracellular sodium concentration measured in erythrocytes.