Variation of calcium current during the cell growth cycle in mouse hybridoma lines secreting immunoglobulins

Ca currents of the cell membrane were recorded during a four-day culture period using the whole-cell variation of the patch electrode voltage clamp on a mouse myeloma cell line (S194, non-secreting) and on two mouse hybridoma cell lines (MAb2-1 which secretes immunoglobulin G (IgG) and MAb7B which secretes immunoglobulin M (IgM]. The density of Ca current increased during the four-day culture period after cells were transferred into fresh medium. The average value of the maximum inward current per cell reached 57 +/- 15 pA (mean +/- S.D.) by the fourth day in hybridomas secreting immunoglobulins. The density of Ca current in hybridomas secreting IgG and IgM was greater than that in non-secreting myeloma throughout the four days of the culture cycle. The cell density showed a sigmoidal increase during the culture period and the rate of increase in the density showed no significant correlation with the density of Ca current. The immunoglobulin level in the medium increased over the culture period, as did the estimated immunoglobulin secretion per cell per day. The time course of the increase of estimated individual cell secretion resembles that of the increase of density of Ca current.