Atrial natriuretic peptide and water and electrolyte transport in the human jejunum.

Abstract

The effects of atrial natriuretic peptide were investigated on water and electrolyte transport in the human jejunum. Six healthy male volunteers (aged 21-33 years) were studied using a triple lumen perfusion technique. A plasma like electrolyte solution containing polyethylene glycol (5 g/l) as a non-absorbable marker was perfused into the jejunum at 10 ml/min, and net water and electrolyte transport and transepithelial potential difference were measured. Subjects were studied single blind on two occasions with either intravenous atrial natriuretic peptide (6 pmollminlkg for 90 minutes) or placebo (saline), both after controlled sodium intake over three days. Plasma atrial natriuretic peptide concentrations rose from (mean (SD)) 10-3 (3.6) pmol/l to a peak of 96-0 (61.8) Atrial natriuretic peptide is a hormone which has been found in a variety of species.' The 126-amino acid propeptide is synthesised and stored in atrial myocytes. The most important biologically active natriuretic peptide released into the circulation is a atrial natriuretic peptide, the 99-126 fraction at the C-terminal end. In humans acute volume load with saline, high sodium intake, or conditions with increased extracellular volume such as chronic heart and renal failure, result in increased plasma atrial natriuretic peptide concentrations.2 Intravenously infused synthetic human a atrial natriuretic peptide in normal subjects induces diuresis, natriuresis, and haemoconcentration,`can lower blood pressure,5 and inhibits renin and aldosterone secretion.6 Given these effects, it seems likely that atrial natriuretic peptide has a physiological role in the regulation of sodium balance and extracellular volume. Atrial natriuretic peptide receptors are found in various organs including the jejunum of the rat. 78 The effect of this hormone on small intestinal transport has not been extensively studied and the available data in animals`" and humans'2 are controversial. Our aim was therefore to investigate whether human atrial natriuretic peptide, infused intravenously in doses simulating pathophysiological blood concentrations, has an effect on water and electrolyte transport in the human jejunum using the triple lumen perfusion technique. MethodsSix normal male volunteers aged 21-33 years (mean 24 years) were studied. Informed written consent was obtained from all subjects and the study protocol was approved by the Otago Hospital Board Ethics Committee. STUDY PROTOCOLEach subject was studied on two separate occasions at least one week apart, once with intravenous atrial natriuretic peptide and once with placebo. The subjects were on a specially composed diet with fixed sodium and potassium intakes of 150 and 70 mmol/day respectively for three days before each study. They were not admitted to hospital for this period. On the third day of the diet a 24 hour urine collection was made to measure electrolyte excretion and creatinine clearance. One subject did not complete the 24 hour collection on one occasion and all his urine baseline data fo...

Atrial natriuretic factor (ANF) does not affect ion transport in human intestine but does in porcine intestine

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