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.