PROSTAGLANDINS INDUCE CALCIUM INFLUX IN HUMAN SPERMATOZOA

Progesterone, prostaglandin and follicular fluid are reported to enhan ce the acrosome reaction through the influx of extracellular calcium i nto the cytoplasm of human spermatozoa. Prostaglandins are present wit hin the male reproductive tract, and high concentrations of prostaglan dins exist in seminal fluid. In order to investigate the mechanisms by which prostaglandins enhance the acrosome reaction through calcium in flux, the intracellular calcium response induced by progesterone, pros taglandin E-1 (PGE(1)), prostaglandin E-2 (PGE(2)) and follicular flui d was measured using fura-2. PGE(1) and PGE(2) promoted calcium influx dose dependently through dihydropyridine insensitive calcium channels . Refractoriness of the elevation of intracellular Ca2+ concentration ([Ca2+](i)) to a second stimulus occurred when 60 mu g/ml PGE(1) was a dministered 100 s after the prior administration of 60 mu g/ml of PGE( 1), and similarly when 1 mu g/ml of progesterone was administered 100 s after the prior administration of 1 mu g/ml of progesterone, Refract oriness also occurred when 60 mu g/ml PGE(1) was administered after th e prior addition of 60 mu g/ml PGE(2), but did not occur between PGE(1 ) and progesterone. Pertussis toxin (PTX) did not modify the changes i n [Ca2+](i) after the addition of PGE(1) or PGE(2). In conclusion, PGE (1) and PGE(2) promoted calcium influx through PTX-insensitive calcium channels which appeared to be recognized by a common receptor differe nt from that of progesterone.