CAMP PROMOTES GAP JUNCTIONAL COUPLING IN T84 CELLS

The effect of intracellular adenosine 3',5'-cyclic monophosphate (cAMP ) on dye and electrical coupling was studied in T84 cells, a cell line often used as a model for epithelial cell fluid secretion. Injections of lucifer yellow (LY) into single cells within a cluster of control cells resulted in LY localization to 1.3 +/- 0.2 (mean +/- SE) cells w ithin a cluster. Twenty-six percent of control T84 cell pairs were ele ctrically coupled as assayed by the dual patch-clamp technique. Treatm ent of cells with agents that either increase intracellular cAMP and/o r activate protein kinase A (PKA) increased dye localization to 3.8 +/ - 0.6 cells and the proportion of electrically coupled cell pairs to 6 5%. No electrical coupling was observed in the presence of the Rp dias tereomer of adenosine-3',5'-cyclic monophosphothioate (Rp-cAMPS), a PK A antagonist. Excess of Rp-cAMPS prevented cell coupling elicited by 2 0 mu M of the Sp diastereomer of adenosine-3',5'-cyclic monophosphothi oate. Expression of connexin 32 mRNA, but not of connexins 26, 43, or 45, was detected by reverse transcription-polymerase chain reaction. T hese results suggest that communication between T84 cells is modulated by PKA, providing a mechanism for regulating multicellular activity, such as fluid secretion.