Abstract
This study investigated whether a cyclic adenosine 3',5'-monophosphate (cAMP) analogue, cBiMPS, could induce hyperactivated motility in frozen-thawed Japanese Black bull spermatozoa and compared the ability of spermatozoa to undergo hyperactivation between fertile and subfertile bulls. Frozen-thawed spermatozoa from 3 fertile and 2 subfertile bulls were washed, suspended in BO-Hepes medium and incubated in the presence of 0.1 mM cBiMPS for up to 4 h. At 1-h intervals, the spermatozoa were examined for hyperactivated motility. The proportions of spermatozoa showing a circular swimming pattern with asymmetrical flagellar beating and those showing whiplash beating of flagella to the total number of motile spermatozoa were expressed as C% and W%, respectively. The motile spermatozoa % was barely affected by treatment with cBiMPS or the fertility status of the sperm donor, although it gradually decreased in all sperm samples during the 4-h incubation. In the fertile bulls, the C% was 0% at 0 h of incubation but rapidly increased during the 1-h incubation with cBiMPS. It then decreased slightly towards 4 h concomitantly with a gradual increase in W% towards 4 h. In the subfertile bulls, however, the cBiMPS-induced increase of C% was delayed for 1-3 h, although the incubation time-related changes in mean W% were similar between the fertile and subfertile bulls. In the vehicle controls for cBiMPS, the C% and W% were 0% throughout incubation for all the samples examined. The results suggest that hyperactivation of the flagellum can be induced by the cAMP analogue, cBiMPS, in frozen-thawed Japanese Black bull spermatozoa and that induction of hyperactivation may serve as a useful tool for detection of functional abnormality of spermatozoa from subfertile Japanese Black bulls.
