Characterization of intracellular Ca(2+) increase in response to progesterone and cyclic nucleotides in mouse spermatozoa.
Rises in intracellular Ca(2+) concentration ([Ca(2+)](i)) caused by progesterone, an inducer of the acrosome reaction, or by cyclic nucleotides, possible second messengers, were investigated by Ca(2+) imaging of the head of individual mouse sperm. Progesterone induced a [Ca(2+)](i) rise in a dose-dependent manner (4-40 microM), primarily in the postacrosomal region. For 20-microM progesterone, Ca(2+) responses occurred in 42% of sperm, separated into two types: transient type (60% of responding cells; duration, 1-1.5 min; mean amplitude, 335 nM) and prolonged type (40%; >3 min; 730 nM). Prolonged responses required higher doses of progesterone, and their occurrence was enhanced significantly by preincubation for 2-4 h as compared with transient responses. 8-Bromo-cGMP (0.3-3 mM) induced a [Ca(2+)](i) rise more effectively than did 8-bromo-cAMP. For 1-mM 8-bromo-cGMP, 90% of cells exhibited transient Ca(2+) responses (approximately 1 min; 220 nM), independently of the preincubation time. In Ca(2+)-free medium, most sperm showed no Ca(2+) response to progesterone and 8-bromo-cGMP. Pimozide, a Ca(2+) channel blocker, completely blocked prolonged responses and partially inhibited transient responses. These results suggest that progesterone activates at least two distinct Ca(2+) influx pathways, with fast or slow inactivation kinetics, and some sperm show both types of response. A cyclic nucleotide-mediated process could participate in the progesterone-induced [Ca(2+)](i) rise.
Kobori
H
H
Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.
Miyazaki
S
S
Kuwabara
Y
Y
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D020101:Acrosome Reaction / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D010868:Pimozide / Q000494:pharmacology; D011374:Progesterone / Q000502:physiology*; D013075:Sperm Capacitation; D013094:Spermatozoa / Q000187:drug effects* / Q000378:metabolism*
D002121:Calcium Channel Blockers; D010868:Pimozide; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D011374:Progesterone; D000242:Cyclic AMP; D006152:Cyclic GMP; D002118:Calcium