Effects of cold on renal sodium and potassium excretion were estimated in 11 subjects aged 21 years, who had a family history of hypertension from either one or both parents, and in 12 subjects matched for age, sex and body surface without any family history of hypertension. After three days of controlled diet containing 230 mmol sodium and 87 mmol potassium, renal excretion of sodium and potassium was measured hourly in each subject during water diuresis and expressed in relation to excretion of creatinine. These variables were estimated hourly for 12 h over two days at a room temperature of 26 °C. Three hours of the second day were spent in bathing suit at a room temperature of 15 °C. During cold exposure sodium excretion increased in normal subjects whilst it decreased significantly in subjects genetically predisposed to hypertension, even during the recovery phase. Under the same experimental conditions potassium excretion increased in both groups during and after cold exposure. At a temperature of 15°C arterial blood pressure increased similarly in both groups whilst heart rate did not change. These results indicate that young males with a genetic predisposition to hypertension show an abnormality in the renal handling of sodium which is revealed by the stress of cold.
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