Functional characterization of cell-to-cell coupling in cultured rat aortic smooth muscle.
Gap junction (GJ) occurrence and function was studied in cultured rat aortic smooth muscle cells, since cell-to-cell coupling is proposed to coordinate smooth muscle function but is difficult to study in the intact tissue. Cell proliferation in vitro formed a multilayered structure 10-15 cells thick. GJs connected cells to lateral and vertical neighbors, appearing in freeze fracture as P-face particles aggregated into circular plaques but also as linear arrays. The membrane potential was 58 +/- 3 mV. From quantification of the spread of electrotonic potentials according to a two-dimensional model, the intercellular resistivity was 900-1,400 omega X cm, whereas the nonjunctional membrane resistivity was 10(4) omega X cm2. Intercellular spread of 5(6)-carboxyfluorescein (CF; mol wt 376) in aortic cultures suggests that metabolic coupling is an important consequence of GJs in smooth muscle. CF transfer was not blocked by A23187 (10(-5) M), although rat fibroblasts became uncoupled by 10(-6) M. Ultimately uncoupled by the more potent ionophore ionomycin (10(-5) M), aortic cells seem more able to maintain GJ permeability during challenge from increased intracellular Ca than cells of noncontractile origin.
D000818:Animals; D001011:Aorta / Q000166:cytology*; D000001:Calcimycin / Q000494:pharmacology; D002450:Cell Communication; D002455:Cell Division; D002477:Cells / Q000145:classification; D002478:Cells, Cultured; D004594:Electrophysiology; D004987:Ethers / Q000494:pharmacology; D007365:Intercellular Junctions / Q000648:ultrastructure; D015759:Ionomycin; D008297:Male; D008854:Microscopy, Electron; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains
D004987:Ethers; D000001:Calcimycin; D015759:Ionomycin