A remarkable increase in the pHi sensitivity of voltage-dependent calcium channels occurs in human sperm incubated in capacitating conditions.
Human sperm are endowed with voltage-dependent calcium channels (VDCC) that produce increases in [Ca2+]i in response to depolarization with KCl. These channels are stimulated during "capacitation", a complex biochemical process, accompanied by a slight pHi alkalization, that sperm must accomplish to acquire the ability to fertilize the egg. The stimulation can be explained in part by the fact that in non-capacitated sperm, calcium influx through VDCC is stimulated by pHi alkalization in the range of pHi observed during capacitation. In this work, we explored the effect of pHi on VDCC in capacitated sperm loaded with fura ff. Strikingly, the pHi sensitivity of VDCC increased approximately 7-fold when sperm was capacitated, as compared with non-capacitated sperm. This finding suggests that the pHi sensitivity of VDCC can be modulated during capacitation so that a combined effect of pHi alkalization and biochemical regulation enhances calcium influx through these channels.
Neri-Vidaurri
Paloma del Carmen
Pdel C
Departamento de Farmacología, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad Universitaria, CP 04510, Apartado Postal 70-297 México, DF, México.
Torres-Flores
Víctor
V
González-Martínez
Marco T
MT
D000293:Adolescent; D000328:Adult; D000468:Alkalies / Q000494:pharmacology*; D000643:Ammonium Chloride / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects* / Q000502:physiology; D005456:Fluorescent Dyes / Q000032:analysis; D016257:Fura-2 / Q000031:analogs & derivatives / Q000032:analysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport / Q000187:drug effects; D008297:Male; D013075:Sperm Capacitation / Q000502:physiology*; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*
D000468:Alkalies; D015220:Calcium Channels; D005456:Fluorescent Dyes; D000643:Ammonium Chloride; C087512:fura F; D002118:Calcium; D016257:Fura-2