Intestinal iodide secretion and its dependence upon mucosal I- permeability

Abstract

Iodide secretion across different regions of rat small intestine has been investigated in vitro using the standard Wilson-Wiseman technique.Net I- secretion was observed along the entire small intestine, being significantly higher in the central region.Anaerobic conditions, ouabain (2 mM) and Na+ free Ringer solution prevented net I- secretion, whilst both theophylline (1 mM) and carbachol (0,1 mM) enhanced the observed basal intestinal I- secretion.Furthermore, Ca2+-deprived bathing solutions significantly reduced intestinal I- secretion.Epithelial I- uptake from both mucosal and serosal sides was measured by using a Ussing-type chamber technique.The initial rate of I- uptake across the mucosal membrane was significantly higher in the central region than in the proximal part of rat small intestine.No significant differences were observed in the rate of I- uptake from the serosal side.These studies suggest that mucosal I- permeability might determine the direction of net I- intestinal transport and that cytosolic Ca2+ may be a physiological regulator of intestinal I- transport.