THE UNCOUPLING EFFECT OF DIACYLGLYCEROL ON GAP JUNCTIONAL COMMUNICATION OF MAMMALIAN HEART-CELLS IS INDEPENDENT OF PROTEIN-KINASE-C

Possible regulatory effects on cell-to-cell communication of a synthet ic diacylglycerol, an activator of protein kinase C (PKC), were examin ed in pairs of synchronously beating ventricular myocytes of neonatal rats in primary culture. Junctional communication was estimated by mea suring either the rate constant of dye diffusion, with the fluorescenc e recovery after photobleaching technique, or the cell-to-cell electri cal conductance with a double whole-cell voltage clamp. The addition o f a freshly prepared emulsion of 1-oleoyl-2-acetyl-sn-glycerol (OAG, 1 00 mu g/ml), either in the bath or in the solution filling the patch p ipet, was seen to interrupt intercellular communication within approxi mately 8 to 10 min. This effect is neither mimicked by stimulation of PKC by a phorbol ester, nor prevented by PKC inhibitors, making it unl ikely that, in these cells, PKC activation could induce intercellular uncoupling. During OAG exposures, the intracellular calcium concentrat ion was very modestly increased (by a factor 1.5 to 2), which does not suffice to account for uncoupling. GAG might trigger interruption of cell-to-cell communication by a mechanism analogous to that of other l ipophilic molecules (such as aliphatic alcohols or long chain unsatura ted fatty acids) which interfere with gap junctions. (C) 1994 Academic Press, Inc.