Effects of hypertonic saline infusion and water drinking on atrial peptide

This study was undertaken to define the changes in plasma levels of atrial natriuretic peptide (ANP) induced by hypertonic saline infusion followed by spontaneous water drinking and to determine whether these changes in ANP are correlated with changes in right atrial pressure (RAP) and plasma levels of vasopressin (AVP). Conscious dogs (n = 5) were infused with hypertonic saline (6%) at a rate of 1.4 ml/min for 4 h. Water was withheld for the first 2 h and administered ad libitum for the final 2 h. Hypertonic saline infusion induced increases (P less than 0.05) in plasma osmolality (posM), pAVP, mean arterial pressure (MAP), and RAP (1.9 +/- 0.6 to 3.1 +/- 0.7 mmHg). These changes were accompanied by an increase of pANP (68 +/- 14 to 120 +/- 33 pg/ml, P less than 0.05). Spontaneous water drinking (1,410 +/- 127 ml) returned posM and pAVP to control levels and produced a further and significant increment in RAP (150%) and pANP (100%). During the water-drinking phase MAP was not further altered, and hematocrit decreased by 11.1% (P less than 0.05). A positive linear correlation (P less than 0.001) was found between increases in RAP and pANP. The administration of an AVP vasopressor antagonist in a similar protocol, and before hypertonic saline infusion, inhibited the increase of MAP, but it did not alter the changes of posM, hematocrit, RAP, nor pANP. These results suggest that changes in the release of ANP during increases in posM and after spontaneous water drinking are predominantly controlled by changes in RAP.(ABSTRACT TRUNCATED AT 250 WORDS)