Water metabolism in diabetes mellitus.
Transcellular shifts of water and changes in the physiology of water excretion are common in diabetes mellitus and its treatment. Recent evidence indicates that hyperglycemia in diabetic patients, but not in normal subjects, is characterized by elevations of circulating levels of arginine vasopressin (AVP; antidiuretic hormone, ADH). The role and importance of these observations remain to be defined since elevations of plasma AVP levels do not decrease water excretion in diabetic patients. Certain oral sulfonylureas, notably chlorpropamide and tolbutamide, are known to decrease renal free water clearance (CH2O), whereas insulin increases CH2O; the insulin and tolbutamide effects may be clinically trivial, whereas that of chlorpropamide is important. The hyponatremic effect of chlorpropamide may be exaggerated in diabetic patients by concomitant diuretic therapy. Euglycemia during chlorpropamide therapy appears to allow full expression of the action of chlorpropamide on CH2O; hyperglycemia with attendant osmotic diuresis protects chlorpropamide-treated patients against hyponatremia. Inhibition of prostaglandin synthesis with nonsteroidal anti-inflammatory agents enhances expression of the ADH effect on the kidney, but it does not appear to potentiate chlorpropamide hyponatremia. Two other oral sulfonylurea agents, tolazamide and glyburide, increase CH2O. Diazoxide is an antihypertensive thiazide which is antidiuretic as well as hyperglycemic. Thus, abnormalities of water metabolism are common in diabetes mellitus. Whether certain of these abnormalities are clinically important depends upon the presence of the osmotic diuresis of hyperglycemia and the pharmacology of diabetic management.[1]References
- Water metabolism in diabetes mellitus. Davis, F.B., Davis, P.J. Am. J. Med. (1981) [Pubmed]
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