Effects of cryoprotectant treatments on bovine sperm function and osmolyte content.

The hypothesis that addition and removal of cryoprotectants to and from spermatozoa would initiate regulatory volume decrease, and lead to osmolyte loss and reduced sperm function, was tested. Common cryoprotectants, in the absence of freezing and thawing, affected bovine ejaculated spermatozoa by lowering their total and progressive motility in medium, reducing their migration through surrogate cervical mucus, damaging sperm head membranes and inducing sperm tail coiling. Sperm function was slightly better maintained after cryoprotectants were added and removed in multiple small steps rather than in a single step. The intracellular content of the polyol osmolytes, D-sorbitol and myo-inositol, exceeded that of the zwitterion osmolytes, L-carnitine and L-glutamate. Certain cryoprotectants reduced intracellular L-carnitine and L-glutamate concentration but not that of myo-inositol or D-sorbitol. Multistep treatments with some cryoprotectants had advantages over one-step treatments in mucus penetration depending on the original amount of intracellular carnitine and glutamate in the spermatozoa. Overall, sperm quality was best maintained by multistep treatment with glycerol and propanediols that were associated with decreased intracellular glutamate concentration. Bovine spermatozoa seem to use glutamate to regulate cryoprotectant-induced cell swelling.

Multistep and single-step treatment of human spermatozoa with cryoprotectants.

OBJECTIVE: To compare the impact of multi- and single-step addition of cryoprotectants on human spermatozoa. DESIGN: Human semen was subjected to cryoprotective agents (CPAs) in both one-step and multistep protocols before removal of the CPAs by multi-step and single-step methods. SETTING: Infertility clinic. PATIENT(S): Healthy normozoospermic volunteers. INTERVENTION(S): Single- and multistep addition and removal of a range of CPAs. MAIN OUTCOME MEASURE(S): Analysis of tail morphology and total and progressive motility, as well as kinematic parameters, in medium and sperm penetration into artificial mucus. RESULT(S): While no CPA drastically affected sperm vitality, some were more deleterious than others. Propane-1,3-diol was the least damaging to sperm function, whereas glycerol and ethyl(hydroxymethyl)propane were particularly disruptive. For all CPAs, multistep addition and removal of CPAs proved less damaging to sperm function than the single-step protocol. CONCLUSION(S): Optimal CPAs may be those that minimize osmotic stresses to spermatozoa during prefreeze and post-thaw procedures.

Norethisterone enanthate has neither a direct effect on the testis nor on the epididymis: a study in adult male cynomolgus monkeys (Macaca fascicularis).

OBJECTIVE: Norethisterone enanthate (NETE) is evaluated in trials of hormonal male contraception. It has been speculated that progestins may exert their contraceptive effects not only by suppressing gonadotropins but also by direct effects on male organs. NETE was given to monkeys in which endogenous gonadotropin secretion was suppressed by a gonadotropin releasing hormone (GnRH) antagonist, and replaced by human follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG). If NETE has a direct effect on spermatogenesis and/or epididymal function, some changes in testicular histology, sperm motility and/or morphology should occur soon after exposure to NETE. METHODS: Fifteen adult intact male monkeys were grouped and treated for a 38-day period. Group I received GnRH antagonist, FSH, hCG and NETE while group II received a regime identical to group I without NETE and group III received only NETE and vehicle. Ejaculates, body weight, testicular biopsies and volume, and hormones were evaluated. RESULTS: There was a similar pattern of serum FSH and testosterone in groups I and II. Testicular volume and the proportion of tubuli exhibiting spermatids was significantly decreased in group III. There were no significant differences between group I and group II in any parameters measured. The forward progression of sperm was not affected by NETE treatment. The consistently low percentages of grade c sperm indicated no sign of hyperactivation. No changes in the gross morphology of the acrosome were detected. CONCLUSIONS: Short-term NETE treatment has neither a direct effect on the testis nor on the epididymis in this nonhuman primate model and its contraceptive effects appear to be exerted exclusively through gonadotropin suppression.