title: Potassium increases intracellular calcium simulating progesterone action in human sperm.
abstract: Progesterone (P) and zona pellucida are known to induce acrosome reaction in human sperm by increasing cytosolic calcium. High concentrations of potassium ions (K+) improve the rate of acrosome reaction in human sperm in vitro. This article determined whether the effect of K+ on the acrosome in human sperm is mediated by increasing intracellular calcium ([Ca2+]i). The effect of K+ on [Ca2+]i was examined by using Fura 2 as the fluorescent indicator. The effect of K+ and P on [Ca2+]i in sperm and the involvement of ion channels was compared. Motile sperm were collected by the swim-up method from semen of healthy volunteers and capacitated overnight in BWW containing 0.5% BSA. Incubation of capacitated sperm with different concentrations of potassium chloride (1.25-20 mM) resulted in dose-dependent increase in [Ca2+]i similar to that observed with P. The increase in [Ca2+]i by K+ and P was blocked by the addition of EGTA, a Ca2+ chelator. K+-induced change in [Ca2+] was not altered by the addition of dihydropyridine derivatives. The combined treatment of K+ (20 mM) and P (0.75 microg/mL) caused an additive effect on the increase in [Ca2+]i. It would appear that human sperm plasma membrane possess different Ca2+ channels responsive to P and K+.
authors.affiliation: Department of Ob/Gyn, Nassau County Medical Center, East Meadow, New York 11554, USA. skumar@ncmc.edu
authors.forename: S
authors.initials: S
authors.lastname: Kumar
authors.forename: Y K
authors.initials: YK
authors.lastname: Ying
authors.forename: P
authors.initials: P
authors.lastname: Hong
authors.forename: V T
authors.initials: VT
authors.lastname: Maddaiah
mesh_terms: D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D011188:Potassium / Q000502:physiology*; D011374:Progesterone / Q000378:metabolism; D013075:Sperm Capacitation; D013094:Spermatozoa / Q000378:metabolism*; D015044:Zona Pellucida / Q000502:physiology
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D011374:Progesterone; D011188:Potassium; D002118:Calcium