AJP - Gastrointestinal and Liver Physiology, Vol 255, Issue 1 18-G26, Copyright © 1988 by American Physiological Society

ARTICLES

Norepinephrine induces Na+-H+ and Cl -HCO3 exchange in Amphiuma intestine: locus and response to amiloride

J. F. White and C. F. Hinton
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322.

Catecholamines stimulate Na+-dependent acid secretion by Amphiuma small intestine. Studies were undertaken to localize the response within the mucosa and characterize the effect on Na+ and Cl- transport. Stripped segments of jejunum were mounted in tissue chambers that permitted isolation of villus or intervillus epithelium. In Cl-free medium, norepinephrine (NE) stimulated the transepithelial voltage (Vms) in both villus and intervillus epithelium, whereas galactose and valine elevated Vms predominately in the villus. Paired segments of whole mucosa were maintained under short circuit while the rate of acid secretion (JH) was measured by titration of the unbuffered serosal medium and unidirectional fluxes of Na+ were measured by 22Na. NE significantly stimulated net Na+ absorption (JNanet), short circuit current (Isc), and JH. Amiloride reduced JH and Isc in NE-stimulated tissues and blocked the stimulation of JNanet by NE. The NE-induced current was nearly completely and reversibly inhibited by replacement of luminal medium HCO3- or CO2. NE significantly stimulated net Cl- absorption without changing Isc or JH. It is concluded that cells throughout the mucosa respond to catecholamines with enhanced Na+ and Cl- absorption, possibly through induction or stimulation of Na+-H+ and Cl- -HCO3- exchange.