Abstract
Polymyxin B (PMB) has been reported to beneficial for boar semen storage by neutralizing endotoxin while PMB has also been shown to directly affect signalling molecules in somatic cells. This study aimed to examine the direct effect of PMB on boar spermatozoa. Ejaculated boar spermatozoa stored with BTS extender at 17°C were washed, incubated with various concentrations of PMB (0–100 µM) for 20 min, examined subjectively for percentages of total and progressive motillity, vigour grade (0–4) and agglutination score (0–4) and stained by propidium iodide for viability. In separate experiments, spermatozoa were preincubated with PMB (0–0.5 µM) for 10 min, stimulated for acrosomal exocytosis with calcium and calcium ionophore A23187 and fixed with glutaraldehyde at 5, 10 and 15 min. Per cent total motility and viability were not significantly different between 0 and 50 µM PMB with gradual decline at higher concentrations while progressive motility was significantly reduced at 25 µM or higher concentrations of PMB. Vigour grade was decreased at 75 µM or higher concentrations but agglutination scores were not affected. Preincubation with PMB resulted in a dose-dependent increase in per cent acrosomal exocytosis by 0.01–0.05 µM PMB at 10 min and by 0.05–0.5 µM at 15 min. These results show that PMB has direct effect on boar sperm motility, viability and acrosomal exocytosis.
