Fig. 2. Effects of store Ca²⁺-ATPase inhibitors on resting [Ca²⁺]_i in individual human sperm. (A) Responses of eight cells to 1 µM thapsigargin (thaps, bar above traces). Most cells failed to respond at this dose (lines without symbols) but a small proportion (approx 5%) generated a brief increase in fluorescence lasting approximately 1 minute (). Inset shows mean response of all cells in this experiment (thapsigargin added at arrow). (B) Responses of seven cells to 10 µM thapsigargin At this concentration thapsigargin (bar above traces) caused a sustained elevation of [Ca²⁺]_i in 35% of cells, a small proportion generating an initial transient (). An example of a cell that failed to respond to 10 µM thapsigargin is shown (). Inset, mean response of all cells in this experiment (thapsigargin added at arrow). (C) Responses of six cells to 10 µM bis-phenol (bar above traces). Bis-phenol caused a clear rise in [Ca²⁺]_i in 70% of cells. Most cells generated a sustained response that was preceded by a transient elevation (,). Inset, mean response of all cells in this experiment (bis-phenol added at arrow). (D) Responses of four cells to 40 µM bis-phenol (bar above traces) in `Ca²⁺-free' sEBSS (no added Ca²⁺). In this saline bis-phenol caused a clear rise in [Ca²⁺]_i in 74% of cells. Responses resembled those in standard EBSS. Upon reintroduction of standard EBSS containing Ca²⁺ (upward arrow) all cells showed a marked rise in [Ca²⁺]_i. Inset, mean response of all cells in this experiment (bis-phenol added at arrow).