Specific strychnine binding sites on acrosome-associated membranes of golden hamster spermatozoa |
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Authors: | Llanos Miguel N Ronco Ana M Aguirre María C |
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Affiliation: | Unidad de Hormonas y Receptores, INTA, Universidad de Chile, Casilla # 138-11, Santiago, Chile. mllanos@uec.inta.uchile.cl |
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Abstract: | This study demonstrates for the first time, that membrane vesicles originated from the hamster sperm head after the occurrence of the acrosome reaction, possess specific strychnine binding sites. [3H]Strychnine binding was saturable and reversible, being displaced by unlabeled strychnine (IC(50)=26.7+/-2.3 microM). Kinetic analysis revealed one binding site with K(d)=120nM and B(max)=142fmol/10(6) spermatozoa. Glycine receptor agonists beta-alanine and taurine inhibited strychnine binding by 20-30%. Surprisingly, glycine stimulated binding by about 40-50%. Results obtained in this study strongly suggest the presence of glycine receptors-with distinctive kinetic properties on the periacrosomal plasma membrane of hamster spermatozoa. Localization of this receptor fits well with its previously proposed role in acrosomal exocytosis during mammalian fertilization. |
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Keywords: | Hamster sperm Acrosome reaction Glycine receptors Strychnine binding Taurine β-alanine |
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