Influence of canine cumulus oophorus on homologous sperm motility

Storage and release of spermatozoa from the pre-uterine tube reservoir

In mammals, after coitus a small number of spermatozoa enter the uterine tube and following attachment to uterine tube epithelium are arrested in a non-capacitated state until peri-ovulatory signalling induces their detachment. Whilst awaiting release low numbers of spermatozoa continually detach from the epithelium and the uterine tube reservoir risks depletion. There is evidence of attachment of spermatozoa to uterine epithelium in several species which might form a potential pre-uterine tube reservoir. In this study we demonstrate that: (1) dog spermatozoa attach to uterine epithelium and maintain flagellar activity, (2) in non-capacitating conditions spermatozoa progressively detach with a variety of motility characteristics, (3) attachment is not influenced by epithelial changes occurring around ovulation, (4) attachment to uterine epithelium slows capacitation, (5) capacitated spermatozoa have reduced ability to attach to uterine epithelium, (6) under capacitating conditions increased numbers of spermatozoa detach and exhibit transitional and hyperactive motility which differ to those seen in non-capacitating conditions, (7) detachment of spermatozoa and motility changes can be induced by post-ovulation but not pre-ovulation uterine tube flush fluid and by components of follicular fluid and solubilised zona pellucida, (8) prolonged culture does not change the nature of the progressive detachment seen in non-capacitating conditions nor the potential for increased detachment in capacitating conditions. We postulate that in some species binding of spermatozoa to uterine epithelium is an important component of the transport of spermatozoa. Before ovulation low numbers of spermatozoa continually detach, including those which are non-capacitated with fast forward progressive motility allowing the re-population of the uterine tube, whilst around the time of ovulation, signalling from as-yet unknown factors associated with follicular fluid, oocytes and uterine tube secretion promotes the detachment of large numbers of capacitated spermatozoa with hyperactive motility that may contribute to the fertilising pool.

Effects of Hyaluronic Acid on Ca²⁺ Influx, Lactate Dehydrogenase Activity, and Cyclic AMP Synthesis in Canine Ejaculated Sperm during <i>In Vitro</i> Capacitation

The effects of hyaluronic acid, which comprises the cumulus intercellular matrix, on Ca(2+) influx, lactate dehydrogenase (LDH) activity, and cyclic AMP synthesis in canine sperm during capacitation was investigated. Ejaculated sperm were collected from 10 Beagle dogs and the sperm were incubated for 4 hr in Eagle's MEM containing 10 microg/ml of hyaluronic acid. The percentages of actively motile sperm, hyperactivated sperm (HA-sperm), acrosome-reacted sperm (AR-sperm), and sperm labeled with fluoresceinated Ca(2+) indicator (Ca(2+)-labeled sperm) were evaluated to assess Ca(2+) influx into the sperm. LDH activity and cAMP concentration were measured in homogenized sperm. The mean percentages of motile sperm, HA-sperm, and Ca(2+)-labeled sperm in the MEM containing hyaluronic acid were higher than in the control medium (P<0.05, 0.05, and 0.01, respectively), but there was no difference between the percentages of AR-sperm. Mean LDH activity and mean cAMP concentration were also significantly higher than the control values (P<0.05). The percentages of HA-sperm correlated with those of Ca(2+)-labeled sperm (r(2)=0.810). The results indicate that hyaluronic acid increases Ca(2+) influx, LDH activity, and cAMP synthesis in canine ejaculated sperm during capacitation in vitro.

Disappearance of the PHA-E Lectin Binding Site on the Surface of Ejaculated Sperm and Sperm Capacitation in the Dog

Ejaculated semen and cross sections of the cauda epididymides collected from 3 normal dogs were smeared or stamped on glass slides, and the sperm on the slides were stained with 7 different FITC-lectins (Con A, DBA, GS-1, PHA-E, PSA, UEA-1, WGA) to examine the relation between sperm-binding glycoprotein derived from the canine prostate and sperm capacitation. The only lectin that stained the ejaculated sperm but not the cauda epididymal sperm was PHA-E. The sperm ejaculated by 5 other dogs were incubated for 4 hr in fluid flushed from the uterine horns or oviducts of estrous bitches, and then the percentages of actively motile sperm and hyperactivated sperm (HA-sperm) were determined. The percentages of PHA-E-labeled sperm and sperm labeled with fluoresceinated Ca indicator to assess the influx of Ca into the sperm were also evaluated. The mean percentages of actively motile sperm, HA-sperm, and Ca-labeled sperm after 4 hr of incubation in the uterine flush fluid and oviductal flush fluid were significantly higher than in control medium (P<0.05, 0.01), but the mean percentages of PHA-E-labeled sperm were lower (both P<0.01). The percentages of PHA-E-unlabeled sperm correlated with the percentages of both HA-sperm and Ca-labeled sperm (r(2)=0.787 and 0.812, respectively). The results indicate that loss of the glycoprotein secreted by the canine prostate on the sperm surface induces the influx of Ca into the sperm, and then hyperactivation of the sperm.