Atrial natriuretic peptide secretion in response to volume expansion and contraction in normal man

The plasma concentrations of ANP in response to isotonic saline-induced volume expansion and furosemide-induced volume contraction in 12 healthy men were measured by radioimmunoassay. The total ANP content was calculated by multiplying the circulating plasma volume (CPV) with the plasma ANP concentration, assuming that most of the ANP remained in the blood vessels. In addition, extracellular fluid volume (ECFV) was measured. After overnight dehydration, plasma ANP concentration significantly increased after isotonic saline was infused, but the urinary ANP concentration did not change essentially. After furosemide-induced volume concentration, plasma ANP concentrations significantly decreased, but the urinary ANP concentrations did not change essentially. As the CVP and ECFV changed, the total plasma ANP also changed. The correlation between these effects was highly significant (r = 0.84 and 0.67, N = 11, respectively). The chromatogram obtained from the plasma in the dehydrated state showed that the area of the high molecular weight ANP peak was relatively large compared with the total area of all ANP peaks. This area of the high molecular weight ANP peaks decreased after saline infusion. In the urine, only the alpha-ANP peak was noted and no high molecular weight ANP peak appeared in the chromatogram. These results indicate that amount and type of ANP secretion may change depending on circulating plasma volume.