EFFECTS OF INSULIN TREATMENT ON BODY FLUID VOLUMES AND PLASMA RENIN ACTIVITY IN DIABETES MELLITUS

Abstract

The effects of insulin treatment on body fluid volumes and plasma renin activity were studied in 7 normotensive non-ketotic diabetic patients. Blood and urine samples were obtained for measurements of fasting blood glucose, daily excretion of urinary glucose, hematocrit, plasma renin activity and plasma aldosterone concentration on the control days of poor metabolic control and twice a week after starting the treatment with insulin. The dosage of insulin was increased by the levels of fasting blood glucose. Body fluid volumes were also measured on the control days and on the 14th day after starting the treatment ; plasma volume and extracellular fluid volume were determined by dilution of Evans blue and sodium thiocyanate, respectively.After starting the treatment, hematocrit decreased and both plasma volume and extracellular fluid volume increased significantly, accompanied by a fall in fasting blood glucose and daily excretion of urinary glucose. Plasma renin activity decreased significantly from 3.9 = 1.6 ng/ ml/hr on the control days to 0.7 ± 0.3 ng/ml/hr on the 14th day ; however, plasma aldosterone concentration did not change. The increase in body fluid volume may be attributable to a sodium-retaining effect of insulin on the kidney and a decrease in osmotic diuresis of urinary glucose. The increase in body fluid volumes may contribute to a fall in plasma renin activity. Further studies are needed to elucidate the reason why plasma aldosterone concentration did not alter.