Effect of caltrin I on the progesterone-induced acrosome reaction in mouse epididymal and ejaculated sperm

CONRADO AVENDAÑO; ANAHÍ FRANCHI; LAURA C. GIOJALAS; CARLOS E. CORONEL

Villa General Belgrano, Córdoba, Argentina.

Congreso; XIV Jornadas Científicas de la Sociedad de Biología de Córdoba; 2003

Sociedad de Biología de Córdoba

It is known that clatrin I (calcium transport inhibitor) binds to the acrosomal region on the head of epididymal sperm and inhibits acrosomal proteases release and/or activity by blockage of extracellular Ca2+ uptake and spontaneous acrosome reaction (AR). To analyze if caltirn affects the activity of progesterone, a physiologic inducer of the acrosomal exocytosis, the functional state of epididymal and ejaculated sperm submitted to in vitro capacitation and induction of AR by addition of 15 µM progesterone was evaluated using the chlortetracycline fluorescence assay (CTC). Epididymal spermatozoa were capacitated sperm recovered from the female reproductive tract 2-4 h post-coitus were maintained in capacitacion medium in the absence of caltrin. In the last cells, the presence of bound caltrin was confirmed by indirect immunofluorescence. Epididymal spermatozoa showed 15.1 % spontaneous AR in absence of caltrin while 8.5 % was recorded in presence of the protein. Ejaculated spermatozoa showed 7.2% spontaneous AR. By addition of progesterone the spontaneous AR of epididymal sperm increase to 41.1 and 49.7 % in absence and presence of caltrin respectively and to 42% in ejaculated spermatozoa. Results indicate that caltrin inhibition on extracellular Ca2+ uptake reduces premature exocytosis to guarantee acrosomal integrity required for sperm-zona pellucid primary binding but does not interfere with the AR promotes action of progesterone.