Impact of acute and chronic sodium loading on atrial natriuretic peptide and renin in man

The relationship between the renin-angiotensin system and the atrial natriuretic peptide and its contributions to the control of sodium balance is not clarified. We therefore studied plasma renin concentration (PRC) and plasma levels of atrial natriuretic peptide (ANP) in normal subjects during acute and chronic salt loading. Acute intravascular volume expansion by iv infusion of 2000 ml of normal saline resulted in sharp rise in plasma ANP from 122 +/- 24 to 405 +/- 141 pg/ml (p less than 0.05). This increase was only transient with plasma ANP returning to control levels after 240 min. In contrast, reduction in plasma renin concentration was less pronounced, however it was persistent for up to 240 min paralleled by a reduction in plasma protein. Reciprocal changes in ANP plasma levels and PRC were observed during dietary modification in sodium intake. At the end of low sodium diet over 4 days, supine plasma ANP averaged 49 +/- 7 pg/ml and levels increased to 128 +/- 38 pg/ml after 6 days of high sodium intake in 11 healthy subjects (p less than 0.05). In contrast, PRC values averaged 69.8 +/- 19.8 microU/ml and 14.4 +/- 6.5 microU/ml during low and high sodium diet respectively (p less than 0.01). The inverse relation between PRC and ANP was seen after prolonged dietary sodium loading over 15 days in 8 additional subjects.(ABSTRACT TRUNCATED AT 250 WORDS)