CALCIUM AND POTASSIUM CURRENTS IN PORCINE GRANULOSA-CELLS MAINTAINED IN FOLLICULAR OR MONOLAYER TISSUE-CULTURE

We studied membrane currents in granulosa cells (GC), immediately afte r collection or after variable culture time in the everted-follicle wa ll or in the monolayer. GC in both systems express an inward calcium c urrent (I(Ca)) with T-type kinetics and voltage dependence. GC in the everted-follicle culture express an outward potassium current (I(K)) k inetics, which remains unchanged during three days in culture. I(K) ha s delayed-rectifier kinetics, but is insensitive to TEA, 4-AP and apam ine. GC in monolayer culture develop a new, inactivating delayed-recti fier potassium current (I(nK)), which progressively dominates as cells advance from day one to day three in culture. A similar I(nK) was rec orded in large luteal cells. A possible link between luteinization and the appearance of I(nK) is hypothesized.