Effect of caltrin protein on rat sperm physiology

MIRANDA, SD; NOVELLA, ML; MALDERA, JA; CUASNICÚ, PS; CORONEL, CE

Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

Caltrin (calcium transport inhibitor), the small and basic protein from seminal vesicle secretion binds to the head of rat epididymal sperm covering specifically the acrosomal region, and inhibits extracellular calcium uptake (Coronel et al., JBC 265:6854, 1992). We also demonstrated that rat caltrin inhibits the activity of trypsin and acrosomal proteases as well as the discharge of acrosomal enzymes probably by inhibition of spontaneous acrosomal exocytosis (Winnica et al., Biol Reprod 63:42, 2000). To obtain more information about the functional role of caltrin on sperm physiology, we examined the effect of this protein on rat sperm capacitation and acrosomal exocytosis (AE) by analyzing protein tyrosine phosphorylation and acrosomal hyaluronidase release of epididymal spermatozoa incubated under capacitation conditions. Percentages of acrosome reacted sperm were also evaluated. The presence of caltrin in the incubation medium did not modify the pattern of sperm protein tyrosine phosphorylation but inhibited hyaluronidase release and reduced the percentage of AE. Viability and motility were not affected by the protein. Data suggest that rat caltrin prevents acrosomal exocytosis withoutaffecting the mechanisms of sperm capacitation that involve protein tyrosine phosphorylation.