Fig. 6. Comparison of the potencies of thapsigargin and bis-phenol in their effects on [Ca²⁺]_i oscillations in human spermatozoa, Ca²⁺ store ATPase activity and mobilisation of stored Ca²⁺. (A) Dose-dependence of the percentage inhibition by thapsigargin of ATP-dependent Ca²⁺ uptake by rat cerebellar microsomes () and arrest of progesterone-induced [Ca²⁺]_i oscillations in human spermatozoa (). Results are the mean±s.e.m. percentage of cells continuing to oscillate after application of thapsigargin; three to six experiments were performed. (B) Dose-dependence (expressed as a percentage of the maximum) of thapsigargin-induced elevation of [Ca²⁺]_i in intact HL-60 cells () (Demaurex et al., 1992) and adrenal glomerulosa cells () (Ely et al., 1991) and dose-dependence of the percentage of oscillating cells in which thapsigargin caused arrest (). (C) Dose-dependence of effects of inhibition by bis-phenol of ATP-dependent Ca²⁺ uptake by rat cerebellar microsomes (), Ca²⁺ ATPase activity in pig cerebellar microsomes (whole, ; or in the presence of 1 µM thapsigargin, ) and arrest by bis-phenol of progesterone-induced [Ca²⁺]_i oscillations in human spermatozoa (; mean±s.e.m. percentage of cells continuing to oscillate after application of bis-phenol). (D) Dose-dependence of the mobilisation of Ca²⁺ by bis-phenol in HL-60 cells (in EGTA-buffered Ca²⁺-free saline; ) (Brown et al., 1994) and arrest of progesterone-induced [Ca²⁺]_i oscillations in human spermatozoa by bis-phenol ().