Stimulation of the zona-free hamster ova penetration efficiency by human spermatozoa after 17 beta-estradiol treatment

Detection of aromatase, androgen, and estrogen receptors in bank vole spermatozoa

Spermatozoa are highly specialized cells which transport a single-copy haploid genome to the site of fertilization. Before this, spermatozoa undergo a series of biochemical and functional modifications. In recent years, the crucial role of androgens and estrogens in proper germ cell differentiation during spermatogenesis has been demonstrated. However, their implication in the biology of mature male gametes is still to be defined. Our study provides evidence for the first time that aromatase, the androgen receptor (AR), as well as the estrogen receptors α and β (ERα and ERβ), are present in bank vole spermatozoa. We demonstrated the region-specific localization of these proteins in bank vole spermatozoa using confocal microscopy. Immunoreactive aromatase was observed in the proximal head region and in both the proximal and distal tail regions, whereas steroid hormone receptors were found only in the proximal region of the sperm head. Protein expression in sperm lysates was detected by Western blot analysis. Immunohistochemical results were analyzed quantitatively. Our results show that bank vole spermatozoa are both a source of estrogens and a target for steroid hormone action. Moreover, the presence of aromatase and steroid hormone receptors in the bank vole spermatozoa indicates a potential function of these proteins during capacitation and/or the acrosome reaction.

Nongenomic steroid action: controversies, questions, and answers

Steroids may exert their action in living cells by several ways: 1). the well-known genomic pathway, involving hormone binding to cytosolic (classic) receptors and subsequent modulation of gene expression followed by protein synthesis. 2). Alternatively, pathways are operating that do not act on the genome, therefore indicating nongenomic action. Although it is comparatively easy to confirm the nongenomic nature of a particular phenomenon observed, e.g., by using inhibitors of transcription or translation, considerable controversy exists about the identity of receptors that mediate these responses. Many different approaches have been employed to answer this question, including pharmacology, knock-out animals, and numerous biochemical studies. Evidence is presented for and against both the participation of classic receptors, or proteins closely related to them, as well as for the involvement of yet poorly understood, novel membrane steroid receptors. In addition, clinical implications for a wide array of nongenomic steroid actions are outlined.

Zona-free sperm penetration assay and inducers of the acrosome reaction: a model for sperm microinjection under the zona pellucida

In order to minimize the percentage of false-negative results in the zona-free sperm penetration assay (SPA), a wide range of substances and/or physical agents capable of inducing the acrosome reaction (AR) have been incorporated in the incubation medium. These agents can also be used for treatment of severe male infertility using the technique of sperm microinjection under the zona pellucida (SMUZ). In the present review, the percentages of acrosome-reacted spermatozoa induced by several physiological, biochemical or physical agents published in the literature are compared in order to find the most efficient method(s) of inducing the AR in human sperm as a previous requirement of optimizing the technique of SMUZ. A working estimate of the level of efficiency of a given AR inducer is calculated by adding up its range score in each of three different arrangements from the highest to the lowest value of percentages of AR and differences in percentages of AR and penetration indexes between treated and control groups in SPA. The agents able to induce the AR by nonphysiological (electropermeabilization, lysophosphatidyl choline, and freezing-thawing) have better positions in this hierarchical system than those ones which require the active participation of sperm membrane receptors or second messenger systems (progesterone, zona pellucida, and stimulators of protein kinase A). Electropermeabilization appears to be the most efficient AR inducer. However, more possibilities need to be explored to enhance the relatively low percentages of acrosome-reacted spermatozoa shown by infertile men.

Comparative study on the use of human follicular fluid or egg yolk medium to enhance the performance of human sperm in the zona-free hamster oocyte penetration assay

A prospective study was conducted on 61 unselected semen samples from infertile patients to compare the efficacy of human follicular fluid (hFF) or TEST-egg yolk medium treatment in enhancing sperm performance in the zona-free hamster oocyte penetration (HOP) test. Both hFF and TEST-egg yolk enhanced penetration scores significantly in the HOP test in comparison with the control swim-up sperm preparation. The TEST-egg yolk medium treatment, however, exhibited the highest penetration scores, and there were higher percentages of preparations passing the 10 or 20% penetration rate cut-off point with sperm exposed to the TEST-egg yolk medium than those exposed to hFF. These results indicate that modification of the original HOP-test protocol by incorporation of TEST-egg yolk medium gives a greatly increased penetration rate when compared to the addition of hFF in such a system.

Techniques for improving the accuracy and efficiency of the sperm penetration assay

Six different techniques were evaluated for improving the accuracy and efficiency of the sperm penetration assay (SPA). Flushing and puncture of the oviduct were found to result in similar recovery of eggs from the oviduct, percentage of penetrated eggs, and penetrations per egg. However, the time required to flush the oviduct tended to be longer than for the puncture technique. Exposure of eggs to a 5% formalin solution prior to mounting resulted in fewer ruptured eggs, greater recovery of eggs, and a reduced time to mount and read the eggs compared to eggs not exposed to formalin. The percentage of penetrated eggs and penetrations per egg were similar for formalin exposed and nonexposed eggs. Significantly fewer penetrated eggs and penetrations per egg were noted when eggs were read as fresh mounts compared to eggs that were fixed and stained prior to evaluation. A significantly longer time was also required to read the freshly mounted eggs compared with the stained eggs. The results of these studies indicate that to maximize the accuracy and efficiency of the SPA, cumulus masses should be removed from the oviducts by puncture, eggs should be placed in a 5% formalin solution before mounting on slides, and eggs should be fixed and stained prior to evaluating for penetrations.

Factors affecting penetration of zona-free hamster ova

The sperm penetration assay is an expensive, time-consuming test to assess male fertility in vitro. Although some investigators are enthusiastic in its application, others feel that it is not sensitive or specific enough to be used as part of the routine infertility evaluation. Indeed, this bioassay is not a faithful reproduction of in vivo conditions. However, if the SPA is abnormal, it is unlikely that sperm will fertilize a human ovum in vivo. Conversely, a normal SPA does not guarantee successful in vivo fertilization. No bioassay can be absolute in its predictive value, but false-negative results must be kept to a minimum for this bioassay to be of any clinical significance. Each laboratory performing the SPA should optimize the assay for sensitivity, reproducibility, and minimization of false-negative results and then establish normal and abnormal ranges of its own. If the limitations of the SPA are kept in mind, and if we employ it very selectively, it may still be useful.

Evaluation of computerized analysis of sperm movement characteristics and differential sperm tail swelling patterns in predicting human sperm in vitro fertilizing capacity

Multivariate discriminant analysis was used to evaluate the usefulness of computer image analysis of sperm movement characteristics and differential patterns of sperm tail swelling after hypoosmotic treatment for predicting the human sperm in vitro fertilizing capacity assessed by the zona-free hamster egg penetration assay. Fifty-five semen samples, mostly normospermic, from untreated infertility clinic patients were analyzed. The % normal sperm morphology, linearity of seminal sperm movement, seminal sperm head beat frequency, mean and maximum amplitudes of lateral head displacement, and hypoosmotic sperm tail swelling patterns c, d and f were selected by multivariate discriminant analysis to be capable of discriminating the samples exhibiting the presence or the absence of sperm in vitro fertilizing capacity. The % total sperm tail swelling did not give additional information about in vitro fertilizing capacity. These preliminary data suggest that computer image analysis of sperm movement characteristics and differential evaluation of hypoosmotic sperm tail swelling might be useful for the prediction of human sperm fertility. Further prospective studies are necessary to validate their predictive functions.

Stimulation of motility and energy metabolism of spermatozoa from asthenozoospermic patients by 17 beta-estradiol

Spermatozoa from nine asthenozoospermic patients were incubated for 3 h in Krebs Phosphate Ringer (KRP), supplemented or not with 17 beta-estradiol. 17 beta-estradiol increased the mean velocity and maintained the percentage of motility during the first 2 h of incubation. Oxydative metabolism and intracellular ATP concentrations were enhanced, too, whereas glycolysis remained unchanged.

Diagnostic value of sperm function tests and routine semen analyses in fertile and infertile men

The results of routine semen analyses, the zona-free hamster oocyte penetration test, the hypoosmotic swelling test, and semen adenosine triphosphate levels were studied in 66 fertile and 130 infertile men. Multivariate discriminant analysis demonstrated that routine semen parameters including semen volume, sperm count, percent sperm motility, and percent normal spermatozoa in combination could predict the fertility of these patients with 70.4% accuracy. Of the three sperm function tests evaluated, the zona-free hamster oocyte penetration test and the hypoosmotic swelling test were selected by the multivariate discriminant analysis as variables capable of providing significant information on the fertility status of the patients. However, the addition of the results of these two tests to the routine semen analysis did not significantly improve the predictability of fertility. The overall correct prediction rate was 77.6% after incorporation of the results of these two sperm function tests. In this group of subjects, the presently available sperm function tests did not predict the fertility status of a patient with a high degree of accuracy.

Multivariate discriminant analysis of the relationship between the hypo-osmotic swelling test and the in-vitro fertilizing capacity of human sperm

Multivariate discriminant analysis was used to evaluate the usefulness of routine semen parameters and the hypo-osmotic swelling test (HOST) as predictors of the in-vitro fertilizing capacity of human sperm as assessed by the zona-free hamster egg penetration assay (HEPA). Eighty-eight semen samples from untreated patients attending an infertility clinic were analysed. Semen samples were classified into the following three groups before statistical analysis: group 1--positive sperm penetration (greater than or equal to 10%, n = 39); group 2--borderline penetration rates for HEPA (greater than 0% but less than 10%, n = 39) and group 3--negative sperm penetration (0%, n = 10). The percentage of sperm with normal morphology and sperm count were found to be significant in discriminating between semen samples exhibiting different in-vitro fertilizing capacity. These two discriminating variables in combination gave an overall correct classification rate of 45.5%. The multivariate discriminant analysis was also performed after excluding the data of group 2 semen samples (n = 39), which exhibited borderline sperm penetration rates. As a result, three discriminating variables including semen volume, sperm count and the percentage of sperm with normal morphology were selected. These three variables in combination could accurately predict whether a semen sample would exhibit positive sperm penetration (group 1) or negative sperm penetration (group 3) with an overall accuracy of 75.5%. The percentage of swollen sperm after hypo-osmotic treatment was not related to the HEPA result, as determined by linear correlation and multiple regression analyses, and did not give additional information about the in-vitro fertilizing capacity of sperm as evaluated by multivariate discriminant analysis.

TEST-egg yolk buffer storage increases the capacity of human sperm to penetrate hamster eggs in vitro

A total of 85 semen samples from infertility clinic patients were examined to study the effect of storage at 4 degrees C in TES-Tris (TEST)-egg yolk buffer for 24 h on the penetrating capacity of sperm in the zona-free hamster egg penetration assay (HEPA). The mean sperm penetration rate and the fertilization index increased significantly after storage in TEST-egg yolk buffer. Only five out of the 85 samples (5.9%) failed to show any improvement in sperm penetration rate after cold storage. The sperm penetration rate before cold storage showed no significant correlations with routine semen characteristics, semen ATP concentration or the functional integrity of sperm membranes as measured by the hypo-osmotic swelling technique. Significant but low correlations were observed between sperm penetration rate after cold storage and the following semen parameters: sperm count, % motility, total number of motile sperm, % normal sperm morphology, total number of normal sperm, semen ATP concentration and sperm penetration rate before cold storage. Partial correlation analysis revealed that the positive correlation between semen ATP concentration and sperm penetration rate after cold storage was not a direct relationship but was due to the correlation with sperm count. The combination of sperm penetration rate before cold storage, sperm count and % normal sperm morphology accounted for 26.2% of the variation in sperm penetration rate after cold storage by stepwise multiple regression analysis, while sperm penetration rate before cold storage alone explained 13.5% of the variation. The results indicate that TEST-egg yolk buffer treatment can enhance sperm penetration rate in vitro and may be useful in the treatment of impaired sperm fertility.(ABSTRACT TRUNCATED AT 250 WORDS)

A possible mechanism of action of 17 beta-estradiol in stimulation of fertilization in vitro

The effects of 17 beta-estradiol (E2) on sperm-egg interactions in the mouse were investigated. It was shown that E2 induces adhesiveness of the sperm head, expressed as sperm-sperm and sperm-egg binding. Since the concentration dependence of this process was similar to that observed for stimulation of in vitro fertilization by E2, it is suggested that induction of adhesiveness or initiation of processes that cause adhesiveness of the sperm head are of biological significance as preparatory steps for fertilization. Finally, the content of E2 in mouse eggs was determined and found to be 0.2 pg/egg, equally distributed between the oocyte together with the zona pellucida and the follicular cells with their associated intercellular matrix. The intra-ovum concentration is estimated as 10(-6) M.

Seminal plasma transferrin and seminiferous tubular dysfunction

Seminal plasma transferrin levels were assayed in 158 random semen samples collected from normospermic, oligospermic, and azoospermic men, and their relationships with seminal characteristics, sperm fertilizing capacity as assessed by the zona-free hamster ova penetration assay, and serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were evaluated. The concentrations of seminal plasma transferrin in azoospermic, oligospermic and postvasectomy samples were significantly lower than those in normospermic samples. Seminal plasma transferrin concentrations were similar in azoospermia due to obstruction of the reproductive tract or damage to the germinal epithelium. No significant difference in seminal plasma transferrin concentrations was observed in the groups of subjects with normal and elevated FSH or normal and elevated LH. A positive correlation was observed between seminal plasma transferrin concentration and sperm density and between total semen transferrin content and the total number of sperm in the ejaculate. There were no significant correlations between seminal plasma transferrin concentration and sperm motility, percent normal sperm, sperm fertilizing capacity, and serum FSH or LH concentration. The results indicate that seminal plasma transferrin is not a useful marker for Sertoli cell or seminiferous tubular dysfunction. In addition, it is doubtful that measurement of seminal plasma transferrin will yield additional information regarding the fertility potential of semen samples.

Oocyte penetration and acrosome reactions of human spermatozoa. I: Influence of incubation time and medium composition

Washed sperm suspensions were evaluated for their ability to penetrate zona-free hamster oocytes and to exhibit an acrosome reaction in vitro. The percentage of acrosome reactions (AR%) was found to increase with incubation time and increased bovine serum albumin (BSA) concentration. We also found, however, that a remarkably high number of live, unreacted spermatozoa persisted during prolonged incubation in sperm samples obtained from some fertile men. After 22 hrs incubation, the motility of the spermatozoa was higher when the medium was supplemented with 10% human cord serum instead of 3.0% BSA. Penetration rates in hamster oocytes were not significantly different with 10% serum or 3.0% BSA as medium-supplementation. The addition of human instead of bovine serum albumin did not apparently affect the oocyte penetration rate of the spermatozoa.

Spermatozoal fertilizing capacity in polyzoospermia: a preliminary study

Men with the spermatological symptom of polyzoospermia (greater than 250 X 10(6) sperm/ml) have been reported to seldom impregnate their wives. It was the aim of this study to investigate the spermatozoal fertilizing capacity in polyzoospermia by the human sperm and zona-free hamster ova penetration bioassay. General semen characteristics and in vitro spermatozoal fertilizing capacity were studied in 12 polyzoospermic male partners of couples of infertile marriages. The results were compared with those from a control group of normospermic fertile men (n = 22). No significant differences in sperm motility, normal morphology and in vitro spermatozoal fertilizing capacity were found between the two groups. The polyzoospermic men we studied did not appear to have any defect with the spermatozoal fertilizing capacity, as assessed by the heterologous sperm--ova penetration bioassay. The apparent impairment of fertility and higher abortion rate in couples with polyzoospermic male partners, as described in the literature, may be related to chromosomal aberrations and/or other unknown functional defect of the spermatozoa.

Seminal plasma beta-human chorionic gonadotropin (beta-HCG): relationships with seminal characteristics and spermatozoal fertilizing capacity

Seminal plasma beta-human chorionic gonadotropin (beta-HCG) levels were determined in 254 semen samples collected from fertile and suspected subfertile men, and their relationships with seminal characteristics and spermatozoal fertilizing capacity were evaluated. Radioimmunoassayable beta-HCG, as defined by greater than 5 mIU/ml concentration, was demonstrated in only 44.5% of all the samples studied. beta-HCG concentrations were similar in normospermic, oligospermic and azoospermic samples. There were no significant differences in beta-HCG concentration between high-motility and low-motility samples, between normal-morphology and abnormal-morphology samples, and between high-fertilizing capacity and low-fertilizing capacity samples. No significant correlations between the concentrations of beta-HCG and individual parameters of semen analysis and spermatozoal fertilizing capacity among the various groups of samples were observed. The physiological role of seminal plasma beta-HCG is presently uncertain and the relationship of its determination to male fertility requires further investigation.

The relationship between the human sperm hypoosmotic swelling test, routine semen analysis, and the human sperm zona-free hamster ovum penetration assay

The functional integrity of sperm membranes of 270 semen samples collected from fertile men and the male partners in couples with infertile marriages was assessed by the hypoosmotic swelling test and the results correlated with routine semen analysis and the human sperm zona-free hamster ovum penetration assay. Semen samples with abnormal semen parameters had lower values of percentage of swollen sperm after hypoosmotic treatment in comparison with those with normal semen parameters. A weak positive correlation was observed between sperm swelling and sperm morphologic features (r = 0.32, P less than 0.05) and between sperm swelling and sperm motility (r = 0.22, P less than 0.05). Insignificant correlation was observed between sperm swelling and in vitro sperm fertilizing capacity, as assessed by the zona-free hamster ovum penetration assay. The results indicate that the sperm swelling test and the zona-free hamster ovum penetration assay are evaluating different functional qualities of sperm that are apparently not associated with each other.

Molecules that initiate or help stimulate the acrosome reaction by their interaction with the mammalian sperm surface

This review deals with exogenous molecules that stimulate the acrosome reaction (AR) of mammalian sperm in vitro, presumably by acting at the sperm surface. Such molecules may exert their effect(s) by stimulating capacitation and/or by stimulation or initiation of the AR, and they are probably present at one of three putative in vivo sites (also discussed here) for the AR of a fertilizing sperm: the oviductal fluid, the cumulus oophorus matrix, and the zona pellucida. The molecules discussed include serum albumin, hydrolytic enzymes (particularly proteases); hormones including biogenic amines, estradiol, and arachidonic acid metabolites; sulfur-containing beta-amino acids; glycosaminoglycans such as hyaluronic acid; and a zona pellucida glycoprotein. Possible mechanisms to explain the effects of these molecules are also discussed. Several conclusions and suggestions are offered in this review: There is more than one site for the AR of a fertilizing sperm in vitro, depending on experimental conditions and species, but the site(s) at which the AR of a fertilizing sperm occur(s) in vivo is/are still a matter of disagreement; there are a number of molecules that can stimulate or initiate the AR in vitro, and such molecular duplication may also exist in vivo to ensure fertility; and synergistic interaction between some of those exogenous molecules may occur in the stimulation of capacitation and the stimulation or initiation of the AR.

Cross-sectional study of semen parameters in a large group of normal Chinese men

Testicular size, semen characteristics and serum reproductive hormone levels were studied in 1239 normal Chinese men. The mean testicular size of 17 ml in this group of subjects was similar to other reports in Orientals but was smaller than that reported in Caucasians. Semen volume, and the sperm count, motility and morphology were comparable to those described for Caucasian subjects. The cervical mucus penetration test (Kremer's test) and the zona-free hamster egg penetration test were also studied in some of the subjects. Age showed a positive correlation with the serum levels of FSH and LH, which were highly correlated with each other. Sperm concentration and the total sperm count were positively correlated with testicular volume, the length of abstinence, the % of sperm with an oval head, and the zona-free hamster egg penetration test, but were negatively correlated with serum FSH. Sperm motility was negatively correlated with the duration of abstinence but was positively correlated with the % normal sperm. The results constitute a normal data base from Chinese men for comparison with studies in male infertility and fertility regulation.

Clomiphene citrate does not improve spermatozoal fertilizing capacity in idiopathic oligospermia

Clomiphene citrate (CC) was given to 24 men with idiopathic oligospermia at a daily dose of 25 mg (10 subjects) or 50 mg (14 subjects). Sperm concentration increased slightly after CC treatment in both groups. Sperm motility and morphology remained unchanged. Spermatozoal fertilizing capacity as assessed by the zona-free hamster ova penetration test showed no significant change throughout the treatment period. Two pregnancies occurred in the partners of the subjects treated with 50 mg CC/day, but none occurred in the other group. We conclude that oral administration of CC does not improve fertilizing capacity of sperm as measured by the zona-free hamster ova penetration test in idiopathic oligospermia.

Effect of clomiphene citrate on human spermatozoal motility and fertilizing capacity in vitro

The effect of clomiphene citrate (CC) at various concentrations (0.005, 0.05, 0.5, 5, and 50 micrograms/ml) on the in vitro motility and fertilizing capacity of human spermatozoa was studied. Spermatozoa collected from 14 normal men were washed in modified Krebs-Ringer solution (Biggers, Whitten and Whittingham [BWW] medium) and incubated with CC for 5 hours, the period required for spermatozoal capacitation. The percent motilities of spermatozoa were recorded at 0 and 5 hours during incubation with CC. After incubation, the spermatozoa were washed with BWW medium to remove CC before insemination of the zona-free hamster ova. CC caused a significant dose-dependent decrease in the penetration of denuded hamster ova in comparison with the control (P less than 0.05). Significant depressive effect on spermatozoal motility was observed with CC at 0.05 micrograms/ml or higher concentrations (P less than 0.05). These results indicate that (1) CC decreases human spermatozoal fertilizing capacity in vitro and (2) the inhibitory effect on fertilizing capacity could be due to the sperm-immobilizing activity of CC.

Effect of reserpine on fertilizing capacity of human spermatozoa

The effect of reserpine at various concentrations (2 X 10(-6), 2 X 10(-7), 2 X 10(-8), 2 X 10(-9) and 2 X 10(-10) M) on the in vitro fertilizing capacity of human spermatozoa was studied. Spermatozoa collected from presumably fertile men were washed in BWW medium and incubated with different concentrations of reserpine for 5 hr before insemination of the zona-free hamster ova. The spermatozoal penetration of the zona-free hamster ova was scored 6 hr later and the results were analyzed statistically. Reserpine, at all the concentrations tested, caused a significant dose-dependent decrease in the penetration of the denuded hamster ova in comparison to the control (p less than 0.05). The percent motility of spermatozoa decreased as a function of time during the preincubation period to initiate spermatozoal capacitation but there were no significant differences in the values between the control and the reserpine - treated spermatozoa (p greater than 0.05). These findings indicate that reserpine can affect the fertilizing capacity of human spermatozoa in vitro and provide an additional evidence to suggest the prospective use of reserpine as a vaginal contraceptive.

Zona-free hamster egg-sperm penetration assay: I. Testing of human semen fertilizability

The zona-free hamster egg penetration test was performed on semen samples from 21 fertile donors, 57 infertile patients with normal semen parameters, and 63 infertile patients with subnormal spermiogram, as well as on 19 frozen semen samples. In the donor group 100% of the samples gave a positive range of penetration (PRP) of 20-96% with a mean penetration rate (MPR) of 53%, while 84% of the frozen samples showed a PRP of 18-44% and an MPR of 31%. Although 74% of the samples from infertile patients with normal spermiograms gave a PRP of 11-92% and an MPR of 34%, only 46% of the semen samples from the infertile patients with subnormal spermiogram showed a PRP of 21-100% but an MRP of 43%.

Lack of effect of exogenous prolactin on the fertilizing capacity of human spermatozoa in vitro

The effect of exogenous prolactin (PRL) on the fertilizing capacity of human spermatozoa in vitro was evaluated by the zona-free hamster ova penetration assay. Bovine and ovine PRL, in both physiological and pharmacological concentrations, failed to increase the penetration after 5 hr of incubation in vitro. The percent motility of spermatozoa was not influenced by PRL during the incubation period. Exogenous PRL does not affect the fertilizing capacity of human spermatozoa in vitro. The role of prolactin, normally present in seminal plasma and female reproductive tract fluid, in the human spermatozoal capacitation process merits further investigation.

Relationships of seminal plasma prolactin with spermatozoal characteristics and fertilizing capacity in vitro

Seminal plasma prolactin (PRL) levels were determined in 224 semen samples collected from fertile and suspected infertile men, and their relationships with spermatozoal characteristics and fertilizing capacity in vitro were evaluated. PRL concentrations were similar in normospermic and oligospermic samples, but were significantly lower in azoospermic samples. PRL concentrations were significantly higher in samples with high spermatozoal motility than in those with low spermatozoal motility. There were no significant differences in PRL concentrations between normal-morphology and abnormal-morphology samples, and between high-fertilizing capacity and low-fertilizing capacity samples. A low degree of positive correlation was observed between the PRL concentration and the spermatozoal motility. There were no significant correlations between the PRL levels, the other spermatozoal characteristics, and the spermatozoal fertilizing capacity in vitro. These findings indicate that the seminal plasma PRL levels are significantly depressed in azoospermic subjects and suggest that the seminal plasma PRL may play a role in the maintenance of spermatozoal motility. Whether there is a potential function of prolactin in semen on spermatozoal fertilizing capacity, however, cannot be inferred from the present study.

Effects of androgens on fertilizing capacity of human spermatozoa

The potential functions of testosterone and 5 alpha-dihydrotestosterone, the androgens normally present in human seminal plasma, on human spermatozoal physiology were evaluated by studying the effects of these two steroid hormones on the in vitro fertilizing capacity of human spermatozoa. Spermatozoa collected from presumably fertile men were washed in BWW medium and incubated with different concentrations (0, 100, 250, 500, 1000 pg/ml) of testosterone or 5 alpha-dihydrotestosterone for 5 hr before insemination of the zona-free hamster ova. Penetration of the zona-free hamster ova was scored 6 hr later and the results were analyzed statistically. Both testosterone and 5 alpha-dihydrotestosterone, at the concentrations tested, significantly decreased the in vitro penetration of the denuded hamster ova in comparison to the controls (p less than 0.05). A dose-dependent response was also observed for the 5 alpha-dihydrotestosterone tested. These findings indicate that exogenous testosterone and 5 alpha-dihydrotestosterone can inhibit the fertilizing capacity of human spermatozoa in vitro, and suggest that the androgens normally present in human seminal plasma may serve, in part, to prevent premature spermatozoal capacitation before the spermatozoa reach the site of fertilization in vivo.