Primary culture of salamander intestinal epithelial cells from nests: whole cell Na+ currents induced by valine

Abstract

Methods are described for isolating the cell nests, subepithelial clusters of germinative cells, from salamander intestinal mucosa and for growing the nests in culture into polarized monolayers of intestinal epithelial cells. Cells were viable in culture for up to 3 wk. The capacity of the monolayer cells to engage in membrane transport was evaluated using the patch-clamp technique in the whole cell mode. L-Valine (25 mM) induced an inward current in small intestinal cells of 25.8 +/- 5.7 pA and depolarized the cell membrane 14.5 +/- 1.6 mV. L-Alanine and L-phenylalanine were similarly effective, whereas D-valine was ineffective. The Km of the transporter for valine was 90 mM. Replacement of bath Na with tris(hydroxymethyl)aminomethane eliminated the inward current induced by valine. The basal (solute-independent) inward current was also reduced by Na+ replacement. Glucose did not induce a Na+ current. In contrast to the effect of valine on small intestinal cells, large intestinal cells were unresponsive to valine. It is concluded that the cultured small intestinal cells possess Na-amino acid but not Na-sugar cotransport. This profile of behavior is characteristic of undifferentiated small intestinal cells. Primary cultures of salamander small intestinal cells should be useful for studying enterocyte function and the developmental biology of the small intestinal mucosa.