Progesterone accelerates the onset of capacitation in mouse sperm via T-type calcium channels

This study was undertaken to evaluate whether progesterone induces capacita tion of mouse spermatozoa. When sperm were evaluated by chlortetracycline s taining, addition of progesterone significantly increased the proportion of spermatozoa exhibiting the B pattern at 60 minutes of incubation, compared with that before incubation (23 +/- 6.2% vs. 13 +/- 2.9%. p < 0.01) and th at in hTF medium without progesterone (23 +/- 6.2% vs. 13 +/- 4.2%, p < 0.0 1). If the redistribution of proteins in sperm plasma membrane such as prot ein binding calcium ion were defined as capacitation, it could be said that progesterone promoted capacitation of mouse sperm. This progesterone-induc ed capacitation was prevented by depletion of extracellular calcium ion and addition of NiCl2, a T-type calcium channel blocker, although thapsigargin , an inhibitor of Ca2+-ATPase, did not increase the number of capacitated s perm (B pattern; progesterone vs. progesterone + depletion of calcium ion, 18 +/- 3.5% vs. 8 +/- 2.5%, p < 0.05. progesterone vs. progesterone + NiCl2 20 +/- 3.8% vs. 6 +/- 5.2%, p < 01). Furthermore, genistein, a protein tyr osine phosphorylation inhibitor. inhibited progesterone-induced capacitatio n (B pattern; progesterone vs. progesterone + genistein, 20 +/- 3.8% vs. 11 +/- 2.4%, p < 01). In conclusion, progesterone induces capacitation in mou se sperm and this capacitation may be associated with calcium influx and ty rosine phosphorylation.