Increase in plasma atrial natriuretic factor and right atrial area during endogenous and exogenous volume loading in healthy volunteers: effect on plasma renin activity, aldosterone and antidiuretic hormone.

The mechanisms of atrial natriuretic factor (ANF) release and the effects of ANF on plasma renin activity (PRA), plasma aldosterone and plasma antidiuretic hormone were investigated in two groups of normal subjects. One group was studied before and after endogenous volume loading produced by 30 min of head-down tilt. The other group was studied before and after an exogenous volume load in the form of 1 litre of isotonic saline infused over 30 min. Measurements made included right atrial area by two-dimensional echocardiography, PRA, plasma aldosterone, plasma antidiuretic hormone and plasma levels of ANF. There was a significant correlation between the increase in atrial area and plasma ANF concentrations after endogenous and exogenous volume loading. Levels of PRA and plasma aldosterone were suppressed significantly after exogenous volume loading but not after endogenous volume loading. The concentration of plasma antidiuretic hormone was not affected by either procedure. Short-term changes in right atrial pressure appear to regulate the plasma levels of ANF in normal people.