Effect of SLF or IL-3 with Ca²⁺ influx blockers on P815 mastocytoma cells. P815 cells were incubated with either SLF (500 ng/mL; ▪) or IL-3 (25% WEHI-3 conditioned medium; □) with Ca²⁺ channel blockers econazole, ketotifen, or Ni²⁺. In all cases, the proportion of dead cells was determined after 18 hours in culture by counting cells that could or could not exclude Trypan blue. Error bars represent the standard error determined from triplicate measurements.