BNP plasma levels during acute volume expansion and chronic sodium loading in normal men

Since the isolation of porcine brain natriuretic peptide (pBNP) in 1988, many aspects of this new endocrine and paracrine system have been elucidated. However, the precise role of human BNP (hBNP) in the regulation of sodium balance and blood pressure in men is still unclarified. We investigated the impact of acute volume expansion and high sodium intake on ANP and BNP plasma levels of 21 healthy male subjects. Following acute infusion of 2000 ml 0.9% saline into a peripheral vein over 30 minutes in a lying position, ANP levels in plasma increased from 110 +/- 14 pg/ml to 199 +/- 18 pg/ml (p < 0.001), while BNP levels remained constant (26 +/- 3 pg/ml before, 28 +/- 3 pg/ml after volume expansion). In a second experiment we investigated the change of ANP and BNP plasma levels after five days of controlled sodium intake (Here blood tests were taken from the probands in an upright position). ANP levels averaged 42 +/- 5 pg/ml after low and 73 +/- 14 pg/ml after high sodium intake. Before starting the diet, the ANP fasting blood level was 56 +/- 6 pg/ml. During both diets, plasma BNP was not altered significantly, but we found a slight insignificant increase after high sodium intake. At the end of each diet we tested ANP and BNP secretion by a physical exercise in an upright position. After high salt intake, BNP plasma levels rose from 32 +/- 4 pg/ml at rest to 45 +/- 7 pg/ml (p < 0.025) after 15 minutes of exercise, while ANP rose from 73 +/- 14 pg/ml to 120 +/- 20 pg/ml (p < 0.001). These results suggest a different regulation of ANP and BNP in normal subjects. ANP secretion is modulated by volume loading and by low or high salt intake while BNP responses to physical exercise.