Response of salt-loaded rats to abrupt withdrawal of salt

¹ Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina

This study was designed to determine whether transient salt wasting follows the abrupt withdrawal of a salt load in rats. Two groups of 30 rats were pair fed an electrolyte-free diet by gavage. One group received 2.5 mm/day of sodium chloride, the other 15 mm/day; both were given 1 mm/day of potassium. After 55 days, salt was withdrawn and the animals sacrificed at several-day intervals. In part I, specimens of aortic blood and skeletal muscles were obtained for chemical analysis, and the adrenal glands were excised for histologic study. In part II, carcass values for sodium and chloride were obtained. The results were: a) There was no evidence of impaired sodium conservation following abrupt salt withdrawal. b) Histologic study of the adrenal cortices revealed flattened glomerulosa zones in the high-salt group and a striking sequential increase in width following salt withdrawal. Evidence of a renal salt-wasting defect following the abrupt removal of a sustained salt load in rats could not be demonstrated.