FIGURE 4.

U-73122 but not U-73343 inhibits the Epo-stimulated rise in [Ca²⁺]_i in primary human erythroblasts and HEK cells. A, day 10 BFU-E-derived cells. BFU-E-derived erythroblasts were removed from methyl-cellulose culture on day 10 and loaded with Fura Red. Where indicated, some cells were pretreated with the active PLC inhibitor U-73122 or the inactive inhibitor U-73343 during Fura Red loading. B, HEK 293T cells transfected with TRPC3 and Epo-R. Transfected HEK 293T cells were pretreated with the active PLC inhibitor U-73122, the inactive inhibitor U-73343, or medium during Fura Red loading. For all experimental groups, base-line [Ca²⁺]_i and the peak percentage increase in [Ca²⁺]_i above base line were calculated for each cell following monitoring at 2-min intervals for 20 min with digital video imaging. Mean ± S.E. of the peak percentage increase for each experimental condition is shown. 7–28 individual cells were studied for each condition in two experiments. **, a significant difference in [Ca²⁺]_i compared with cells treated with Epo (p < 0.0001).