Loss of Spermatozoa Coating Antigens from Boar Spermatozoa in the Female Genital Tract

Abstract

The present experiment was performed to examine the surface changes in the boar spermatozoa during transport through the female reproductive tract. The spermatozoa coating antigens (SCA) derived from seminal plasma on the surface of boar spermatozoa were observed by an indirect immunofluorescence technique using anti-boar seminal plasma rabbits sera and FITC conjugated anti-rabbit IgG sheep sera. Freshly ejaculated spermatozoa showed bright fluorescence on the acrosomal cap and weak fluorescence on the midpiece and tail, indicating the presence of SCA in these regions. Ovulation was induced in seven proestrous gilts by administration of 500iu HCG, and in 16 post-weaning sows by subcutaneous injection of 1, 000iu PMSG followed by 500iu HCG 56hr later. These gilts and sows were mated with fertile boars and autopsied 3, 6 or 24hr later. Spermatozoa were recovered from the uterine horns and utero-tubal junctions within an hour of autopsy by flushing these tracts with modified Krebs-Ringer bicarbonate solution. The ova recovered from oviducts were stained with aceto-lacmoid and examined for the evidence of fertilization. The spermatozoa recovered from the uterus 3 and 6hr after mating showed loss of SCA in 16.6% and 91.3%, respectively. Spermatozoon was not recovered from the uterus 24hr after mating. All spermatozoa recovered from the utero-tubal junction 6 and 24hr after mating showed loss of SCA. When ejaculated spermatozoa were incubated in vitro 3 and 6hr at 37°C, the immunofluorescence pattern was the same as that of fresh ejaculate. The fertilization rates of ova recovered from the oviduct 3, 6 and 24hr after mating were 5.6% 43.8% and 92.0%, respectively. These results suggest that the SCA on the surface of boar spermatozoa is removed in the genital tract of estrous gilts and sows within 6hr after mating.