Only pharmacological doses of atrial natriuretic peptide affect intestinal ion transport in non-volume expanded rats.

Abstract

Pharmacological doses of atrial natriuretic peptide were infused into rats to study its effect on intestinal transport. Saline control or two concentrations ofrat a atrial natriuretic peptide (0.06 or 1-0 nmollminlkg) were administered intravenously (1 ml) over one hour. Jejunal net transport of water and electrolytes was measured with a plasma-like luminal electrolyte solution using a 'closed loop' technique. Distal colonic potential difference and arterial blood pressure were monitored continuously. Blood samples for analysis of plasma atrial natriuretic peptide concentrations were taken at the end of the experiments. Plasma concentrations were increased (mean (SD) (2.1 (0.5) and 24.0 (1.1) nmol/l respectively) compared with the controls (0.023 (0.016) nmol/l). Blood pressure dropped by 30% (p<005) in both groups of rats receiving atrial natriuretic peptide but remained unchanged when control saline was infused. Jejunal net absorption was reduced (p<0.01) only in animals receiving the higher concentration ofpeptide (H20 from 173 (33) to 64 (69) ,ul.h-lhcm-, Na from 25.7 (5.3) to 10.9 (8.9) ,umol.h-1.cm-2). Distal colonic potential difference was not affected by atrial natriuretic peptide. In conclusion massive doses of atrial natriuretic peptide are required to produce any change in intestinal salt and water transport in normal, non-volume expanded rats; these effects could be a nonspecific or 'toxic' response.

Whey protein hydrolysates enhance water absorption in the perfused small intestine of anesthetized rats

“…It has been reported that the expansion of blood volume inhibits water absorption in the jejunum via atrial natriuretic peptide secreted in response to atrial stretching. 21,22) At equal weights and osmolalities, WPH was more effective than AA in promoting water absorption (Fig. 4A).…”