Effect of calcium on membrane potential behavior in a rat pituitary cell line (GH3).

The effects of intracellular calcium buffering and increasing bath Ca2+ on spontaneous membrane depolarizations expressed by the clonal rat pituitary cell line GH3 were examined by use of the whole-cell patch-clamp technique. Increasing intracellular calcium buffering capacity caused the duration of spontaneous depolarizations to increase without altering other parameters of membrane potential activity. Increasing bath Ca2+ caused a decrease in duration. These results suggest that the duration of spontaneous membrane depolarization in GH3 cells is regulated by the accumulation of free intracellular Ca2+. The behavior of spontaneous depolarizations measured with the perforated-patch variation of whole-cell patch-clamp techniques closely resembled that obtained in standard whole-cell patch-clamp measurements with an intracellular calcium buffer of 200 microM EGTA with free Ca2+ adjusted to 100 nM.