Isotonic volume reduction associated with cAMP stimulation of 36Cl efflux from jejunal crypt epithelial cells

To determine the effect of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) on the isotonic volume of jejunal crypt epithelial cells, we isolated these cells by sequential perfusion using a hyperosmolar Ca(2+)-free solution and measured cell volume electronically. 8-BrcAMP caused rapid shrinkage to a reduced but stable cell volume; this isotonic volume reduction was prevented by either a Cl(-)-channel blocker, anthracene-9-carboxylate (A-9C), or Ba2+, a K(+)-channel blocker. 8-BrcAMP substantially increased the rate of A-9C-sensitive 36Cl efflux from crypt cells; this increased rate of efflux was not influenced by Ba2+ but was abolished by alterations in membrane potential. Following 8-BrcAMP-stimulated isotonic volume reduction, addition of either Ba2+ or A-9C caused the crypt cells to reswell. In contrast, 8-BrcAMP added to enterocytes isolated from the villus compartment did not result in A-9C-sensitive volume reduction or in an increased rate of 36Cl efflux. Our data demonstrate that epithelial cells isolated from jejunal crypt compartments respond directly to cAMP with a rapid volume reduction that is paralleled by an increase in 36Cl efflux through a conductive pathway. Unlike other Cl- secretory epithelial cells, the intestinal crypt cell does not appear to regulate its volume in an isotonic medium after cAMP-induced shrinkage.