title: Replacement of calcium for strontium in hamster sperm incubation media: effect on sperm function.
abstract: Calcium (Ca(2+)) is an absolute requirement for a decisive sperm function event: the acrosome reaction (AR). Physiologically, sperm capacitation is a prerequisite for this specialized exocytosis and both events are intimately related. In an effort to separate capacitation from AR, we have been using a modified sperm incubation medium where Ca(2+) is replaced by Strontium (Sr(2+)). The aim of this report is to analyze with more detail the difference between sperm incubated with Ca(2+) or Sr(2+) in several events. We found that sperm undergo the capacitation-related changes in the chlortetracycline (CTC) pattern and tyrosine phosphorylation, and also bind to the zona pellucida (ZP) when using Sr(2+)-instead of Ca(2+)-containing media. However, the spontaneous AR typical of hamster sperm does not take place in Sr(2+)-medium, even if sperm are previously capacitated with Ca(2+). Nevertheless, Sr(2+) was able to sustain AR when cells were treated with thapsigargin or depolarized with K(+) in Na(+)-depleted medium. Considering that the absence of Na(+) increased spontaneous AR in Sr(2+)-medium, we tested whether Na(+)-transport systems could be involved in the inability of Sr(2+)-incubated sperm to undergo AR. We found that when sperm incubated in Sr(2+)-medium are treated with amiloride to inhibit epithelial Na(+) channel (ENaC), they are able to undergo spontaneous AR. The same result was obtained when analyzing AR on the ZP. On the contrary, addition of ouabain (a Na(+)/K(+)-ATPase inhibitor) or DIDS (a Na(+)/HCO3(-) co-transporter inhibitor) showed no effect. These results suggest that, differing from what happens in Ca(2+)-incubated sperm, cells incubated in Sr(2+)-modified medium would have an active ENaC.
authors.affiliation: Instituto de Biología y Medicina Experimental (IByME) - CONICET, Buenos Aires, Argentina.
authors.forename: Sandra
authors.initials: S
authors.lastname: Bachmann
authors.forename: Renata J
authors.initials: RJ
authors.lastname: Menéndez-Helman
authors.forename: Karina
authors.initials: K
authors.lastname: Zitta
authors.forename: Eva V
authors.initials: EV
authors.lastname: Wertheimer
authors.forename: Patricia V
authors.initials: PV
authors.lastname: Miranda
mesh_terms: D000177:Acrosome / Q000502:physiology; D020101:Acrosome Reaction / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002751:Chlortetracycline / Q000494:pharmacology; D006224:Cricetinae; D003470:Culture Media / Q000737:chemistry*; D005260:Female; D006801:Humans; D008297:Male; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013075:Sperm Capacitation / Q000502:physiology*; D013094:Spermatozoa / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013324:Strontium / Q000378:metabolism*; D015044:Zona Pellucida / Q000378:metabolism
chemical_list: D003470:Culture Media; D011500:Protein Synthesis Inhibitors; D002118:Calcium; D002751:Chlortetracycline; D013324:Strontium