Mechanisms of salt and water retention during pregnancy in the dog.

Changes in the sodium/potassium balance and the renin-angiotensin-aldosterone system during pregnancy were studied in dogs. About 50% of the animals showed a significant increase in aldosterone secretion (P less than .02). Plasma renin substrate (PRS) concentration was consistently elevated while plasma renin activity (PRA) was often but not always high. The administration of estradiol induced sodium retention in normal and adrenalectomized dogs though the response in adrenalectomized animals was not necessarily related to an increase in aldosterone secretion. The administration of deoxycorticosterone acetate depressed the renal excretion of potassium. This decrease seemed related to the administration of estrogens. The plasma concentrations and metabolism of deoxycorticosterone were normal during pregnancy.