ROLE OF SUBSTANCE-P IN WATER HOMEOSTASIS

The effect of the naturally occurring peptide substance P on release of antidiuretic hormone (ADH) was studied in anesthetized dogs. Intravenous infusions of substance P in doses of 0.5, 5.0, and 50 ng/kg/min increased plasma concentrations of ADH in a dose-related fashion. At the two low doses, this increase occured in the absence of changes in urine volume, sodium excretion, free water clearance, and urinary cyclic AMP excretion. In addition, when substance P was administered in a concentration of 0.5 ng/kg/min, plasma levels of ADH were increased even though blood pressure did not change, suggesting that substance P may release antidiuretic hormone by a direct mechanism. Intrarenal infusions at a rate of 0.5 and 5 ng/kg/min caused dose-related decreases in free water clearance and significant increases in urinary cyclic AMP excretion. These data suggest that substabce P may play an important role in the regulation of water balance. © 1979.