Concentrations of volume-regulatory hormones after acute exercise in physically conditioned males

Plasma renin activity and plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP) and aldosterone (Aldo) were determined in six physically conditioned male volunteers and five unconditioned volunteers who served as controls. All volunteers were subjected to acute exercise for 15 min or until exhaustion. In the conditioned volunteers, the plasma concentrations of all hormones did not change when compared with pre-exercise values measured immediately after and 60 min after exercise. Similarly, plasma renin activity (PRA) after exercise was unchanged when compared with pre-exercise levels. In contrast, the unconditioned volunteers showed elevation of the plasma concentrations of AVP, and Aldo. PRA also increased in the unconditioned volunteers, but plasma ANP concentrations were not significantly different from base-line pre-exercise levels. These data suggest a decrease in central volume with exercise in the unconditioned individuals, which probably does not occur in the conditioned individual because of adaptive mechanisms. The data also suggest that in the physically conditioned individual, significant atrial distention with resultant release of atrial natriuretic peptide does not occur, or alternatively, that significant atrial distention in these subjects fails to produce the expected release of atrial natriuretic peptide. In the unconditioned individual, the postulated decrease in effective central volume following exercise would not be expected to trigger any rise in ANP.