DOES PLASMA ANP PARTICIPATE IN NATRIURESIS INDUCED BY ALPHA-MSH

alpha-Melanocyte-stimulating hormone (alpha-MSH; 0.6 and 3 nmol) micro injected into the anteroventral region of the third ventricle (AV3V) i nduced a significant increase in diuresis without modifying natriuresi s or kaliuresis. Intraperitoneal (ip) injection of alpha-MSH (3 and 9. 6 nmol) induced a significant increase in urinary sodium, potassium an d water excretion. Intraperitoneal (3 and 4.8 nmol) oriv (3 and 9.6 nm ol) administration of alpha-MSH did not induce any significant changes in plasma atrial natriuretic peptide (ANP), suggesting that the natri uresis, kaliuresis and diuresis induced by the systemic action of alph a-MSH can be dissociated from the increase in plasma ANP, These prelim inary results suggest that alpha-MSH may be involved in a gamma-MSH-in dependent mechanism of regulation of hydromineral metabolism.