Effect of four different in vitro incubation temperatures on functional dynamics, process of capacitation and apoptosis in goat spermatozoa

Abstract

The present study was intended to divulge the insights into in vitro thermal stress induced capacitation and apoptosis like changes in Barbari buck spermatozoa. Forty eight semen ejaculates were obtained from four adult fertile Barbari bucks, diluted with TALP and further divided into four aliquots. The aliquots were incubated for 2h at four different temperatures e.g., 34, 37, 38 and 40°C. Physical seminal attributes were evaluated by employing standard fluorescent and non fluorescent techniques. Capacitation and acrosome reaction status were evaluated by chlortetracycline assay (CTC) and immunolocalization of tyrosine phosphorylated proteins as indicator of capacitation, while, apoptosis like changes were evaluated by evaluating translocation of phosphatidyl serine and inner transmembrane mitochondrial potential. The percentage of spermatozoa showing capacitation and acrosome reaction was significantly higher (P<0.05) at 38 and 40°C than other incubation temperatures. Similarly, percentage of spermatozoa showing phosphorylation of tyrosine containing proteins was higher at 38 and 40°C. Significant (P<0.05) increase in spermatozoa apoptosis was also recorded in terms of low mitochondrial transmembrane potential and high exteriorization of phosphatidyl serine at 38 and 40°C. Moreover, significant (P<0.05) reduction in spermatozoa motility, viability and intact acrosome was recorded with rise in incubation temperature beyond 38°C. Therefore, it can be concluded that, high incubation temperature induces functional alterations in buck spermatozoa in terms of apoptosis like changes, capacitation through increased phosphorylation of tyrosine containing proteins and acrosome reaction in spermatozoa, and thereby may be responsible for decrease in the quality of spermatozoa.