CHARACTERIZATION OF GAP-JUNCTIONS BETWEEN PAIRS OF LEYDIG-CELLS FROM MOUSE TESTIS

Leydig cells are coupled in vivo by numerous gap junctions. In vivo an d in vitro cells were immunolabeled by connexin 43 (Cx43) but not by C x26 or Cx32 antibodies; immunoblotting confirmed specificity of Cx43 l abeling. Pairs of Leydig cells dissociated from mouse testis were stud ied by dual whole cell voltage clamp, and a high incidence of dye (n = 20) and electrical coupling in = 60; >90%) was found. Coupling coeffi cients were near 1 and junctional conductance (g(j)) averaged 7.2 +/- 1.2 nS (SE, n = 40). Large transjunctional voltage (V-j) decreased g(j ); currents decayed exponentially with time constants of seconds that decreased at greater V-j. The residual conductance at large V-j was at least similar to 40% of the initial conductance. Exposure of cell pai rs to saline solutions saturated with CO2 (n = 15) or containing 2 mM halothane (n = 15) or 3.5 mM heptanol (n = 15) rapidly and reversibly reduced g(j). In eight cell pairs, gating of single junctional channel s was observed during halothane-induced reduction in g(j). Most gating events at V-j < 40 mV were fit by a Gaussian distribution with a mean of similar to 100 pS, With V-j > 40 mV, smaller transitions of simila r to 30 pS were also recorded, and the frequency and duration of the s imilar to 100-pS transitions decreased. Also, similar to 70-pS transit ions between 30- and 100-pS conductances were observed in the absence of 70-pS transitions to or from the baseline, indicating that the 30-p S conductance was a substate induced by large V-j.