Transport of spermatozoa in the reproductive tracts of mares

A scintigraphic method was developed to study sperm migration in the reproductive tracts of mares. Mares (n=5) and stallions (n=2) were used to test various steps of the procedure and three other mares and a stallion were used to study sperm transportation. A radiolabelling solution was prepared from 99mTc (Technetium-99m) and hexamethyl propylene amine oxime. The highest labelling of spermatozoa (57-72%) was obtained by incubation of the spermatozoa with the radiolabelling solution for 20 min at 20 degrees C. Radioactivity outside the spermatozoa was removed by centrifugation and by two subsequent washings with skimmed milk extender. The labelled spermatozoa were inseminated into the uterine bodies of detomidine-sedated mares undergoing oestrus and scintigraphic images were obtained for 4.5 h after insemination. Both dynamic (two pictures s(-1), 2 min multiple scans, 64 x 64 matrix) and static scans (20 s, 64 x 64 matrix) were used to image the mares. The attenuation of gamma radiation in the vagina and uterus was determined for each mare. Radioactive spermatozoa were found in the tips of the uterine horns for the first time at about 8-20 min after insemination. The frequency of uterine contractions varied considerably among mares and ranged from five to 65 contractions during the first 30 min after insemination. Within 1 h after insemination most of the sperm activity was in the uterus. At 2.5 h after insemination, most of the spermatozoa had left the uterus and were either in the vagina or had escaped into the vulva and been discharged. At 4.5 h after insemination there was hardly any sperm activity in the uterus and a small amount of activity only in the vagina; most spermatozoa had been eliminated from the mares.