Recovery of motile membrane-intact spermatozoa from canine epididymides stored for 8 days at 4 degrees C

The purpose of this study was to determine how long canine spermatozoa remain motile and with intact membranes when maintained within epididymides stored at 4 degrees C, and to determine whether such stored spermatozoa are able to bind to canine zonae pellucidae. Testes with attached epididymides, obtained from 32 dogs (26 purebred; six mixed breeds) at orchiectomy, were refrigerated at 4 degrees C, and spermatozoa were collected from caudae epididymides at nine time intervals ranging from 5 to 192 h. The effects on spermatozoa that had been refrigerated within epididymides for various times were determined by assaying sperm motility, integrity of plasma membranes and of acrosomes, and measuring binding of membrane-intact spermatozoa to canine zonae pellucidae. Membrane integrity was assessed using a double fluorescent dye, and acrosome integrity by staining with Pisum sativum agglutinin. For the zona-binding assay at various refrigeration time points, duplicate sets of six oocytes each, isolated from ovaries retrieved at elective ovariohysterectomy, were placed into 100 microliter droplets of sperm capacitation medium containing 5 x 10(6) spermatozoa/ml. One minute later, oocytes were rinsed vigorously by pipetting, and then incubated for 1 h at 38.5 degrees C in a humidified atmosphere of 5% CO2 in air; the number of membrane-intact spermatozoa bound to zonae were counted. There was no significant decrease in membrane integrity and acrosome integrity of spermatozoa recovered from epididymides stored at 4 degrees C within the first 48 h of refrigeration. In contrast, sperm motility decreased significantly within the first 5 h of refrigeration (P < 0.05), but then declined more gradually thereafter. Some spermatozoa recovered from epididymides that had been refrigerated for 192 h retained their capability to bind to zonae pellucidae, although the mean number of refrigerated spermatozoa (0.4) bound to zonae was less than that of fresh samples (9.0). Membrane integrity of spermatozoa recovered from epididymides refrigerated for various times was highly correlated (r = 0.88) with sperm motility. Even after storage for 192 h (8 days) at 4 degrees C, motile spermatozoa could be recovered from the epididymides, and such refrigerated spermatozoa were capable of binding to zonae. We interpreted these data to indicate that it might be possible to recover functional spermatozoa from postmortem specimens of domestic and nondomestic canids.