ADH levels during salt depletion in dogs.

Two groups of trained dogs were subjected to sodium chloride depletion and plasma ADH concentration, renin activity, plasma sodium, plasma osmolality, blood volume, hematocrit and body weight were measured. I n one group of animals, sodium depletion was created by restricting intake to 5 mEq/24 h. Despite a statistically significant decrease in body wcight and blood volume and a corresponding increase in plasma renin activity, plasma ADH concentration was not seen to change significantly from control valnes. Similar findings were seen in a second group of dogs which were given a diuretic in addition to dietary sodium restriction. In these animals the decrease in blood volume and rise in plasma renin activity were proportionately greater. Plasma ADH concentration was not observed to change si,pificantly in this group of animals either. Both groups of animals developed significant hyponatremia during the experiment. It is concluded that in these dogs, the secretion of ADH was not suppressed and consequently hyponatremin developed. It is suggested that endogenous angiotensin was responsible for the continued secretion of ADH at control levels. K e y words: ADH, renin-angiotensin, hyponatremia, salt depletion, blood volume, diuretic. There is no information available regarding plasma concentrations of antidiuretic hormone during sodium chloride depletion. Despite this, many of the alterations in the body fluids attending sodium depletion have been explained on the basis of variations in SDH secretion. An animal in negative sodium balance might be expected to show alterations in ADH levels as volume is lost along u1t.h Na. This report deals with the results of our experiments in which plasma ADH was measured in trained dogs during sodium deprivation.