Effects of saline loading during head down tilt on ANP and cyclic GMP levels and on urinary fluid excretion

Abstract In the present study the renal and humoral effects of acute saline infusions were investigated in six healthy male volunteers before, during and after a ten day period of −6° head-down-tilt (HDT). During the whole 23-day study period the subjects received a standardized diet including 40 ml water and 125 mg NaCl per kg body weight per day. After the infusion of 0.9% saline (22 ml/kg within 20 minutes) plasma atrial natriuretic peptide (ANP) levels were only slightly increased (not significant) at the end of the infusion, while plasma cyclic GMP levels were significantly increased by about 40% (p These data suggest that HDT does not induce major alterations in the regulation of an acute saline infusion and plasma ANP does not play a major role in the diuretic/natriuretic effects of volume loading.