1978 Volume 54 Issue 8 Pages 957-965
To clarify the function of the renin-angiotensin system in diabetes mellitus with or without complications, the responsiveness of plasma renin activity (PRA) to the administration of furosemide was investigated in 32 patients with diabetes mellitus and in 35 age-matched normal subjects. Ten of these diabetic patients had no detectable complications, and the remaining 22 had one or more of the complications of hypertension, nephropathy and neuropathy.
The complicated diabetic patients had a longer history of diabetes mellitus and a greater increase in fasting blood sugar, as compared with the uncomplicated diabetic patients. Eighty mg of furosemide was orally administrated in the early morning.
Blood for the PRA assay was drawn before and 4 hours after the administration of furosemide, and urine was collected for 4 hours after the administration. PRA was measured by the Skinner method.
The mean baseline PRA in uncomplicated diabetic patients was 1.3±0.3 ng/ml/h, not significantly different from that (1.2±0.1) in normal subjects. On the other hand, the mean baseline PRA in complicated diabetic patients was 0.7±0.1 ng/ml/h, significantly lower than in the normal subjects and the uncomplicated diabetic patients. The means of urine volume and sodium excretion after the furosemide administration were unchanged in uncomplicated diabetic patients and significantly lower in complicated diabetic patients, as compared with the normal subjects. The mean PRA after the furosemide administration in uncomplicated diabetic patients was 3.5±0.7 ng/ml/h, not significantly different from that (3.8±0.5) in normal subjects, while the value in complicated diabetic patients was 1.5±0.2 ng/ml/h, significantly lower than in uncomplicated diabetic patients. When the responses of PRA, urine volume and sodium excretion to the furosemide administration were studied in relation to each complication, the hypertensive group had low levels of baseline PRA, decreased responses of PRA, water diuresis and natriuresis to furosemide administration as compared with the nonhypertensive group. The group with neuropathy also had similar findings, as compared with the group without neuropathy. The group with nephropathy had insignificant decreases in the furosemide-induced diuresis and natriuresis, as compared with the group without nephropathy.
These results suggest that the renin-angiotensin system may function normally in uncomplicated diabetes mellitus but not in complicated diabetes mellitus, and that the blunted responsiveness of the renin-angiotensin system to the furosemide administration in complicated diabetes mellitus may be related to an altered renin release in the juxtaglomerular apparatus and the impairment of diuretic and natriuretic functions in the renal tubules secondary to chronic diabetes mellitus.
