Fig. 2.
NO mobilises stored Ca2+ in sperm. (A) Spermine NONOate causes a slowly-developing rise in [Ca2+]i in human sperm. Responses of 4 separate cells are shown. Red trace shows example of cell generating [Ca2+]i oscillations. (B) In low-Ca2+ medium ([Ca2+]o≤5 μM) the response to NONOate was similar, but oscillations were rarely seen. Responses of 7 cells shown. (C) Pseudocolour image series showing NONOate-induced rise in [Ca2+]i in the sperm neck/midpiece. Numbers show minutes since application of 100 μM spermine NONOate. (D) Mean normalised increase in fluorescence 10 minutes after application of 100 μM spermine NONOate to cells bathed in sEBSS (271 cells; 3 experiments) and low-Ca2+ sEBSS (214 cells; 3 experiments). (E) A rapid decrease in [Ca2+]i followed washout of NONOate, followed by slow recovery. Upon re-introduction of NONOate many cells generated oscillations in the neck/midpiece region. Responses of 5 individual cells shown. Lower panel shows pseudocolour images series of a single [Ca2+]i oscillation (numbers show time in seconds).