Effect of BSA on Ca²⁺ influx in mast cells stimulated by ovalbumin

To examine the effect of bovine serum albumin (BSA) on the cell surface of mast cells, we measured ⁴⁵Ca influx in mast cells from actively sensitized rats, and in cells passively sensitized in vitro with IgE-containing serum before or after BSA purification. Mast cells from actively sensitized rats showed a marked increase in ⁴⁵Ca uptake after stimulation by ovalbumin. The uptake of ⁴⁵Ca by mast cells passively sensitized before separation through BSA was also increased in response to ovalbumin. Variation in ⁴⁵Ca uptake increased in the cells sensitized after separation. We did not observe a significant increase in ⁴⁵Ca uptake in mast cells incubated with inactivated or normal serum compared to that of unstimulated cells.