title: Lack of voltage-dependent calcium channel opening during the calcium influx induced by progesterone in human sperm. Effect of calcium channel deactivation and inactivation.
abstract: Progesterone induces calcium influx and acrosomal exocytosis in human sperm. Pharmacologic evidence suggests that voltage-dependent calcium channels (VDCCs) are involved. In this study, membrane potential (Vm) and intracellular calcium concentration ([Ca(2+)](i)) were monitored simultaneously to assess the effect of VDCC gating on the calcium influx triggered by progesterone. Holding the Vm to values that maintained VDCCs in a deactivated (-71 mV) closed state inhibited the calcium influx induced by progesterone by approximately 40%. At this Vm, the acrosomal reaction induced by progesterone, but not by A23187, was inhibited. However, when the Vm was held at -15 mV (which maintains VDCCs in an inactivated closed state), the progesterone-induced calcium influx was stimulated. Furthermore, the progesterone and voltage-dependent calcium influxes were additive. These findings indicate that progesterone does not produce VDCC gating in human sperm.
authors.affiliation: Departamento de Farmacología, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad Universitaria, México, D.F., México.
authors.forename: Alberto Martín
authors.initials: AM
authors.lastname: Guzmán-Grenfell
authors.forename: Marco T
authors.initials: MT
authors.lastname: González-Martínez
mesh_terms: D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology; D000293:Adolescent; D000328:Adult; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D011374:Progesterone / Q000494:pharmacology*; D013094:Spermatozoa / Q000187:drug effects* / Q000502:physiology*; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D007476:Ionophores; D014634:Valinomycin; D011374:Progesterone; D002118:Calcium