THE ROLE OF POSTURE ON THE CHANGES IN PLASMA ATRIAL-NATRIURETIC-FACTOR AND ARGININE VASOPRESSIN LEVELS DURING IMMERSION

In seven healthy male volunteers we investigated changes in plasma atrial natriuretic factor ([ANF]), arginine vasopressin ([AVP]) and plasma volume (PV) during supine immersion. Twenty minutes head-out water immersion in a supine position in a thermo-neutral water bath attenuated the increase in PV induced by 20 min in a supine position in air, but increased the mean plasma [ANF] from 32.0 pg · ml-1, SEM 5.1 to 53.3 pg · m-1, SEM 3.6 and decreased the mean plasma [AVP] from 1.4 pg · ml -1, SEM 0.1 to 0.9 pg · ml-1, SEM 0.04. Simultaneously, diuresis and natriuresis increased markedly. During a 20-min control period in the supine posture without immersion, PV, plasma [ANF] and [AVP] remained unaffected while diuresis and natriuresis did not increase to the same extent. These data suggest that an increase in the central blood volume induced by a weak external hydrostatic pressure during supine immersion triggered the changes in plasma [ANF] and [AVP] and that the increase was probably due to a shift of blood volume from peripheral to central vessels. The changes in plasma [ANF] contributed to the changes in natriuresis. © 1990 Springer-Verlag.