The effect of relaxin and prostaglandin E2 on the motility of human spermatozoa**Supported by grant HD-12395 from the National Institutes of Health and by a grant from the Mellon Foundation.††Presented in part at the Forty-First Annual Meeting of The American Fertility Society, Chicago, Illinois, September 28 to October 2, 1985

Human sperm ion channel (dys)function: implications for fertilization

BACKGROUND

Intensive research on sperm ion channels has identified members of several ion channel families in both mouse and human sperm. Gene knock-out studies have unequivocally demonstrated the importance of the calcium and potassium conductances in sperm for fertility. In both species, the calcium current is carried by the highly complex cation channel of sperm (CatSper). In mouse sperm, the potassium current has been conclusively shown to be carried by a channel consisting of the pore forming subunit SLO3 and auxiliary subunit leucine-rich repeat-containing 52 (LRRC52). However, in human sperm it is controversial whether the pore forming subunit of the channel is composed of SLO3 and/or SLO1. Deciphering the role of the proton-specific Hv1 channel is more challenging as it is only expressed in human sperm. However, definitive evidence for a role in, and importance for, human fertility can only be determined through studies using clinical samples.

OBJECTIVE AND RATIONALE

This review aims to provide insight into the role of sperm ion channels in human fertilization as evidenced from recent studies of sperm from infertile men. We also summarize the key discoveries from mouse ion channel knock-out models and contrast the properties of mouse and human CatSper and potassium currents. We detail the evidence for, and consequences of, defective ion channels in human sperm and discuss hypotheses to explain how defects arise and why affected sperm have impaired fertilization potential.

SEARCH METHODS

Relevant studies were identified using PubMed and were limited to ion channels that have been characterized in mouse and human sperm. Additional notable examples from other species are included as appropriate.

OUTCOMES

There are now well-documented fundamental differences between the properties of CatSper and potassium channel currents in mouse and human sperm. However, in both species, sperm lacking either channel cannot fertilize in vivo and CatSper-null sperm also fail to fertilize at IVF. Sperm-lacking potassium currents are capable of fertilizing at IVF, albeit at a much lower rate. However, additional complex and heterogeneous ion channel dysfunction has been reported in sperm from infertile men, the causes of which are unknown. Similarly, the nature of the functional impairment of affected patient sperm remains elusive. There are no reports of studies of Hv1 in human sperm from infertile men.

WIDER IMPLICATIONS

Recent studies using sperm from infertile men have given new insight and critical evidence supporting the supposition that calcium and potassium conductances are essential for human fertility. However, it should be highlighted that many fundamental questions remain regarding the nature of molecular and functional defects in sperm with dysfunctional ion channels. The development and application of advanced technologies remains a necessity to progress basic and clinical research in this area, with the aim of providing effective screening methodologies to identify and develop treatments for affected men in order to help prevent failed ART cycles. Conversely, development of drugs that block calcium and/or potassium conductances in sperm is a plausible strategy for producing sperm-specific contraceptives.

Seminal plasma metabolites mediate the associations of multiple environmental pollutants with semen quality in Chinese men

Environmental exposure to arsenic, phthalate esters (PAEs) and perfluorinated compounds (PFCs) has been associated with human semen quality. However, the epidemiological "black-box" of these associations remains poorly uncovered. In this study, based on the association analysis between arsenic, PAE and PFC exposure and semen quality parameters (i.e., semen volume, sperm concentration, sperm count, progressive motility, total motility and normal morphology) in a Chinese male population, we explored the seminal plasma metabolic signatures that may mediate the exposure-outcome relations by using the meet-in-metabolite-analysis (MIMA) approach. As a result, a negative association was found between DMA and sperm concentration, whereas MEHP and PFHxS were positively associated with sperm count and concentration, respectively. Metabolomics analysis revealed that sixteen and twenty-two seminal plasma metabolites were related to sperm concentration and count, respectively, and they are mainly involved in fatty acid, lipid and amino acid metabolism. Moreover, it was further indicated that eicosatetraenoate, carnitines and DHA may impact the inverse association between DMA and sperm concentration, while eicosatetraenoate, carnitines, DHA, PGB2 and tocotrienol are possible mediators of the positive association between PFHxS and sperm concentration. As these metabolic biomarkers are relevant to antioxidation and fatty acid β-oxidation, we suggest that redox balance and energy generation shifts in seminal plasma are involved in the association of human semen quality with environmental DMA and PFHxS exposure.

Sperm motility and lipid composition in internally fertilizing ocellate river stingray Potamotrygon motoro

All extant groups of Elasmobranches have internal fertilization and the structure of the male reproductive organs is very specific: sperm passes from the internal organs via the cloaca, but the male copulating organ (clasper) is distant from the cloaca. This suggests that sperm can contact the surrounding medium before fertilization. Because of this involvement with the environment, external signaling in sperm motility activation could occur in these species even though their fertilization mode is internal. In this case, spermatozoa of Elasmobranches should hypothetically possess a specific structure and membrane lipid composition which supports physiological functions of the sperm associated with environmental tonicity changes occurring at fertilization. Additionally, sperm motility properties in these taxa are poorly understood. The current study examined sperm lipid composition and motility under different environmental conditions for the ocellate river stingray, Potamotrygon motoro, an endemic South America freshwater species. Sperm samples were collected from six mature males during the natural spawning period. Sperm motility was examined in seminal fluid and fresh water by light video microscopy. Helical flagellar motion was observed in seminal fluid and resulted in spermatozoon progression; however, when diluted in fresh water, spermatozoa were immotile and had compromised structure. Lipid class and fatty acid (FA) composition of spermatozoa was analyzed by thin layer and gas chromatography. Spermatozoa FAs consisted of 33 ± 1% saturated FAs, 28 ± 1% monounsaturated FAs (MUFAs), and 41 ± 1% polyunsaturated FAs (PUFAs), and a high content of n-6 FAs (32 ± 2%) was measured. These results allowed us to conclude that sperm transfer from P. motoro male into female should occur without coming into contact with the hypotonic environment so as to preserve potent motility. In addition, this unusual reproductive strategy is associated with specific spermatozoa structure and lipid composition. Low level of docosahexaenoic acid and relatively low PUFA/MUFA ratio probably account for the relatively low fluidity of freshwater stingray membrane and can be the main reason for its low tolerance to hypotonicity.

Beneficial effects of relaxin on motility characteristics of stored boar spermatozoa

BACKGROUND

Relaxin is detected in seminal plasma of many species and its association with sperm motility may be beneficial in some aspects of assisted reproduction. Here, we immunolocalized relaxin receptors and investigated the effects of exogenous relaxin on motility characteristics, viability, and cAMP content of boar spermatozoa after storage.

METHODS

Commercial doses of boar semen were obtained on the collection day (Day 0) and kept in shipping containers at room temperature for up to 4 days (Day 4). On Day 0, spermatozoa were fixed for immunofluorescence detection of relaxin receptors RXFP1 and RXFP2 (Experiment 1). Semen aliquots were taken from the same dose at Day 0, Day 1, and Day 2 (Experiment 2a), and Day 2 and Day 4 (Experiment 2b) for analyses. Alive spermatozoa were purified and incubated (1 h-37°C) with 0, 50, or 100 ng relaxin/ml (Experiment 2a) and 0, 100, or 500 ng relaxin/ml (Experiment 2b). Afterward, aliquots of each treatment group were subjected to motility (Experiments 2), viability (Experiment 3) analyses, and cAMP quantification (Experiment 4). Data (3-4 independent replicates) were statistically analyzed (ANOVA followed by pairwise comparisons) and p values less or equal to 0.05 was set for significant difference.

RESULTS

Both RXFP1 and RXFP2 receptors were immunolocalized on the entire spermatozoon. Relaxin concentration of 100 ng/ml significantly improved the proportions of motile, progressive, and rapid spermatozoa up to Day 2. Only 500 ng relaxin/ml provided beneficial effects on Day 4. The viability of spermatozoa was not affected by relaxin (100 ng/ml) during storage, but the extent of mitochondria membrane damages was significantly decreased. Furthermore, relaxin did not affect the cAMP contents of spermatozoa during storage, in our conditions.

CONCLUSIONS

Relaxin could be a valuable motility booster of stored- or aged-spermatozoa for assisted reproduction techniques. However, the related-intracellular signaling cascades of relaxin in boar spermatozoa remain undetermined.

Docosahexaenoic acid supplementation fully restores fertility and spermatogenesis in male delta-6 desaturase-null mice

Delta-6 desaturase-null mice ((-/-)) are unable to synthesize highly unsaturated fatty acids (HUFAs): arachidonic acid (AA), docosahexaenoic acid (DHA), and n6-docosapentaenoic acid (DPAn6). The (-/-) males exhibit infertility and arrest of spermatogenesis at late spermiogenesis. To determine which HUFA is essential for spermiogenesis, a diet supplemented with either 0.2% (w/w) AA or DHA was fed to wild-type ((+/+)) and (-/-) males at weaning until 16 weeks of age (n = 3-5). A breeding success rate of DHA-supplemented (-/-) was comparable to (+/+). DHA-fed (-/-) showed normal sperm counts and spermiogenesis. Dietary AA was less effective in restoring fertility, sperm count, and spermiogenesis than DHA. Testis fatty acid analysis showed restored DHA in DHA-fed (-/-), but DPAn6 remained depleted. In AA-fed (-/-), AA was restored at the (+/+) level, and 22:4n6, an AA elongated product, accumulated in testis. Cholesta-3,5-diene was present in testis of (+/+) and DHA-fed (-/-), whereas it diminished in (-/-) and AA-fed (-/-), suggesting impaired sterol metabolism in these groups. Expression of spermiogenesis marker genes was largely normal in all groups. In conclusion, DHA was capable of restoring all observed impairment in male reproduction, whereas 22:4n6 formed from dietary AA may act as an inferior substitute for DHA.

Relaxin and related peptides in male reproduction

The relaxin hormone is renowned for its function in pregnancy, parturition and other aspects of female reproduction. At the same time, the role of relaxin in male reproduction is still debated. Relaxin is prominently expressed in prostate and its receptors are found in several male reproductive organs; however, the data indicative of its contribution to differentiation and functioning of prostate or testis are contradictory. Prostate relaxin is a main source of this peptide in the seminal plasma. The relaxin effects on sperm motility and fertilization have been reported. The expression of other relaxin related peptides, such as INSL5 and INSL6 was described in testis; yet, currently there are no experimental data to pinpoint their biological functions. The other member of relaxin peptide family, insulin-like 3 peptide (INSL3), is a major player in male development. The INSL3 peptide is expressed in testicular fetal and adult Leydig cells and is directly responsible for the process of abdominal testicular descent (migration of the testes towards the scrotum during male development). Genetic targeting of the Insl3 gene or INSL3 GPCR receptor Lgr8/Rxfp2 causes high intra-abdominal cryptorchidism due to a differentiation failure of testicular ligaments, the gubernacula. Several mutations of these two genes rendering nonfunctional proteins have been described in human patients with testicular maldescent. Thus, in this chapter we review the data related to the expression and function of relaxin and related peptides in male reproduction.

Effect of relaxin on in vitro fertilization of porcine oocytes

Porcine relaxin is a peptide hormone belonging to the insulin super family that has a variety of biological functions. The present experiment was designed to investigate the effects of relaxin on sperm function and on in vitro fertilization (IVF) of porcine oocytes. Porcine spermatozoa were washed, swum-up, and incubated for 1-4 h in mTALP medium supplemented with 0, 20 or 50 ng/ml porcine relaxin. Motility was determined by observing the type of forward movement of the spermatozoa, and acrosome status was evaluated by applying the triple staining technique. Immature oocytes were aspirated from antral follicles and matured in IVM medium (modified NCSU-37). Matured oocytes were co-cultured with spermatozoa in IVF medium (mTALP) supplemented with 0, 5, 10, 15 or 20 ng/ml relaxin. After 6 h of sperm-oocyte co-incubation, putative zygotes were cultured for 18 h in oocyte culture medium NCSU-37 and then assessed for the rates of monospermy, polyspermy, and male pronucleus formation after acetic orcein staining. Relaxin improved (P<0.05) sperm motility and increased the percentage of acrosome-reacted live spermatozoa during 1-4 h of incubation, although viability was not significantly improved. Significantly (P<0.05) the highest percentage of monospermic (31.7%) and lowest percentage of polyspermic (16.5%) fertilization was achieved from the sperm-oocyte co-culture group treated with 20 ng/ml relaxin as compared to other groups. The percentage of male pronucleus formation was significantly (P<0.05) greater in the 20 ng/ml relaxin-treated sperm-oocyte co-culture group than in the other groups. These results indicate that supplementation with relaxin is capable of improving sperm function and fertilization of porcine oocytes in vitro.

In vitro effects of arecoline on sperm motility and cyclooxygenase-2 expression

Semen samples were obtained from 30 volunteers who had never consumed betel quid. Swim-up spermatozoa from the 30 seminal samples of non-betel quid chewers and also non-smokers, usually not exposed to passive smoking, were treated in vitro with arecoline at different concentrations to evaluate the action of these drugs on sperm motility. Highly motile sperms were collected and divided into 5 equal fractions. Four fractions were supplemented with various concentrations of arecoline and one as control. The study was carried out at time 0 and +1, +2, +3 and +4 hr of incubation. Sperm cells were also extracted and blotted with COX-2 antibody after arecoline treatment after 4 hr incubation. The sperm motility parameters, i.e., motility, average path velocity, curvilinear velocity, straight-line velocity and linearity, were significantly decreased after arecoline treatment. In vitro, arecoline induces the COX-2 expression of sperm cells in a dose-dependent manner. This is the first report to demonstrate that arecoline may mediate COX-2 expression in human sperms, resulting in inflammation response. This situation may act on the structure responsible for the flagellar motion and cause the reduction of sperm motility.

Serum relaxin concentrations and reproduction in male bonnethead sharks, Sphyrna tiburo

Relaxin is a 6-kd polypeptide hormone that is responsible for regulating several reproductive processes in female vertebrates, but its role in male reproduction remains unclear. To aid in clarifying this role, the objective of the present study was to investigate changes in endogenous relaxin levels associated with reproductive events in male elasmobranchs, which represent one of only three vertebrate groups known to possess this hormone. Serum relaxin concentrations were measured in 27 immature and 66 mature male bonnethead sharks (Sphyrna tiburo), a species with a well-characterized, seasonal reproductive cycle. Temporal changes in serum relaxin concentrations of immature male S. tiburo were not observed. In contrast, a temporal cycle in serum relaxin concentrations of mature male S. tiburo was observed in individuals from two sampling locations. Significant increases (P<0.05) in serum relaxin concentrations of mature male S. tiburo from both collection sites occurred during late spermatogenesis and the mating period, two critical stages of the reproductive cycle. The results from this study suggest that relaxin may play an important role in regulating semen quality, or other aspects of reproduction in male sharks. This is the first study to demonstrate a temporal pattern in endogenous serum Rlx concentrations associated with reproductive events in feral vertebrates. As such, it strengthens earlier hypotheses that suggested a role for this hormone in regulating male vertebrate fertility and copulatory success.

Seminal immunoreactive relaxin in domestic animals and its relationship to sperm motility as a possible index for predicting the fertilizing ability of sires

Although immunoassayable relaxin has been detected in human and boar seminal plasma, there is no evidence suggesting the existence of immunoreactive relaxin in the seminal plasma of other domestic animals. The first objective of this study was to determine whether immunoreactive relaxin was present in the seminal plasma of bulls, rams and he-goats. In addition, the correlation of immunoreactive relaxin with sperm motility as an index for predicting the fertilizing ability of bull sires was investigated. Semen with normal sperm motility was collected from bulls, rams and he-goats, and the relaxin immunoreactivity of the semen samples was measured using a time-resolved fluoroimmunoassay (TR-FIA) for porcine relaxin that we developed. The presence of relaxin immunoreactivity was demonstrated in seminal plasma from bulls, rams and he-goats. The level of immunoreactive relaxin in seminal plasma was the highest in bulls followed by humans, rams, boars and he-goats in that order, when relaxin levels in boar and human semen having normal sperm motility were also assayed under the same conditions. When the correlation between the seminal plasma level of immunoreactive relaxin and sperm motility was examined in bull semen samples as an index for predicting fertilizing ability, it was found that the relaxin level was significantly correlated with the percentage of spermatozoa showing the most intensive motility (r = 0.64, p < 0.05). These results indicate that immunoreactive relaxin is widely found in the seminal plasma of domestic animals and that measuring the relaxin concentration of seminal plasma may be useful to identify subfertile sires or predict the fertility potential of individual sires.

Growth hormone or insulin-like growth factor-I extends longevity of equine spermatozoa in vitro

Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are both present in blood plasma and IGF-I has been measured in epididymal fluid and seminal plasma. This study was designed to investigate the direct effects of GH or IGF-I on the motility of mature equine spermatozoa in vitro. We compared the effects of one concentration (100 ng/ml) of recombinant bovine GH (rbGH) and recombinant human IGF-I (rhIGF-I) on motility and motion characteristics of equine spermatozoa over a 24 h period. Motility was maintained longer in spermatozoa treated with either rbGH or rhIGF-I during a 24 h period at room temperature (P < 0.05). Spermatozoa motion characteristics at time 0, 1, 2, 4, 6, 12 and 24 h for both rbGH and rhlGF-I were not significantly different from the respective controls. This study has shown that GH and IGF-I are effective in promoting the in vitro longevity of spermatozoa.

Immunoreactive relaxin in seminal plasma of fertile boars and its correlation with sperm motility characteristics determined by computer-assisted digital image analysis

Ejaculates from 10 mature fertile large white Yorkshire boars were used to examine the correlation between immunoreactive relaxin levels in seminal plasma and sperm motility characteristics. Seminal plasma levels of immunoreactive relaxin were measured by a time-resolved fluoroimmunoassay (TR-FIA). Motility characteristics were assessed using a CellSoft computer-assisted digital image analysis system. The mean +/- SD level of immunoreactive relaxin in seminal plasma was 2.61 +/- 0.62 ng/mL. When the correlation between seminal plasma levels of immunoreactive relaxin and parameters of sperm movement was examined, it was found that relaxin levels were significantly correlated with the percentage of motile spermatozoa (r=0.687, p < 0.05), curvilinear velocity (r=0.745, p < 0.05), straight line velocity (r=0.651, p < 0.05), mean amplitude of lateral head displacement (mean ALH) (r=0.844, p < 0.01) and the maximum amplitude of lateral head displacement (max ALH) (r=0.830, p < 0.01), but not with linearity, beat-cross frequency, or percentage of circular cells. Among these parameters, seminal plasma levels of immunoreactive relaxin showed the strongest correlation with the ALH parameter related to fertilizing ability. These results indicate that immunoreactive relaxin in boar semen may be necessary not only for normal sperm motility but also for normal fertility, suggesting that determination of the profile of immunoreactive relaxin in ejaculates may have value as a potential marker for predicting sperm fertilizing ability of boars.

Effects of pentoxifylline on sperm motility in normogonadotropic asthenozoospermic men

Forty-seven normogonadotropic men with idiopatic asthenozoospermic were divided at random: group I (N = 22) received placebo and group II (N = 25) received 1200 mg of pentoxifylline/day during 6 months. Semen analysis was performed basal and at 3 and 6 months of the study period. No statistical changes in serum hormone concentration were found, nor in volume, sperm counts, viability, and morphology before and after treatment. Sperm motility increased following pentoxifylline treatment after 3 and 6 months from 25.5 (21.0-30.0) to 35.5 (31.5-39.0) (p < .00001) and to 42.0 (38.0-46.0) (p < .00001), respectively. Although in the placebo control cases some changes were observed in the sperm motility, they were less significant. Furthermore, progressive motility only in grade A increased with pentoxifylline from 2.5 (0.0-6.0) to 12.0 (6.0-19.5) (p < .001) at 3 months and to 22.5 (17.0-26.0) at 6 months (p < .00001). In conclusion, pentoxifylline had an additional effect rather than placebo and was useful treatment in these cases of male factor infertility.

Intracellular signal transduction mechanisms of rat epididymal spermatozoa and their relationship to motility and metabolism

The role of intracellular signal transduction mechanisms in regulating the motility and metabolism of rat spermatozoa in undiluted caudal epididymal fluid (CEF) was examined. Samples of CEF containing immotile spermatozoa were exposed to drugs and other agents that either stimulate signal transduction pathways or mimic the action of their second messengers. Under these conditions, sperm motility in 25-30 nl of CEF was stimulated by calcium ions (Ca2+), N2,2'-O-dibutyrylguanosine 3':5'-cyclic monophosphate (dibutyryl cGMP), cyclic adenosine 3':5'-monophosphate (cAMP), N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (dibutyryl cAMP), 8-bromoadenosine 3':5'-cyclic monophosphate (8-bromo cAMP), caffeine, theophylline and bicarbonate ions (HCO3-). Other agents such as magnesium ions (Mg2+), veratridine, phospholipase C (PLC), ionophore A23187, 1,2-dioctenoyl-sn-glycerol (DAG), phorbol 12-myristate 13-acetate, phospholipase A2 (PLA2), arachidonic acid, and melittin did not significantly influence motility. In the presence of radiolabelled energy substrates, untreated (immotile) spermatozoa in samples of CEF utilised D-[U-14C]glucose and [1-14C]acetate as exogenous energy sources for oxidative metabolism. No detectable 14C-lactate was produced, and none of the drugs altered the rate of glycolytic or oxidative metabolism. The findings suggest that the motility of rat caudal epididymal spermatozoa is regulated by Ca2+ and the guanylate cyclase and adenylate cyclase pathways, but not through the PLC and PLA2 pathways. Also, their metabolism of exogenous substrate was uncoupled from the induction of motility, and their oxidative capacity exceeded the rate of flux of glucose-carbon through the glycolytic pathway.

Use of theophylline to enhance sperm function

Poor sperm motility is an important factor in male infertility. Preliminary results in our laboratory on a group of 19 men (10 suspected infertile men and 9 fertile donors) showed stimulation of sperm fertilizing ability after sperm washing with theophylline as demonstrated by zona free hamster egg penetration test. The egg penetration rate for the control spermatozoa samples from subfertile men was 16%. Incubation with theophylline (10 mM) increased the penetration rate to 46%, whereas semen incubation with theophylline (20 mM) increased the penetration rate to 51%. A similar twofold increase in egg penetration was observed in the semen of fertile men incubated with theophylline of similar concentrations. Subfertile patients with ejaculate volumes of less than or equal to 1 ml or total motile sperm count of less than or equal to 10 x 10(6)/mL or increased semen viscosity did not exhibit beneficial effects with theophylline washing as measured by hamster egg penetration test score. The increase in percentage of penetrated eggs with theophylline use in both fertile and subfertile men was significant at 10 mM concentration (p less than .001) and 20 mM (p less than .001) when compared to control (untreated) samples. No significant difference in penetration rate was seen between 10 and 20 mM theophylline concentrations. It appears that theophylline may be useful in improving the fertilizing capacity of selected human semen samples with poor motility and poor penetration ability under artificial insemination conditions.

Effect of Sp-cAMP on sperm motility in patients with unexplained infertility

Sperm motility is one of the most important semen parameters affecting the fertility of an individual. Sp-cAMP, a thiophosphate analogue of c-AMP, is a phosphodiesterase inhibitor controlling the intracellular c-AMP levels which in turn influences sperm motility. The results in our laboratory on a group of suspected subfertile men and fertile donors showed significant enhancement of sperm motility after incubation of washed sperm with various doses of Sp-cAMP.

The influence of relaxin on motility of human sperm in vitro

Sperm of healthy men were incubated in an IVF medium with relaxin at concentrations of 3, 30, 300 and 3000 ng ml-1. Immediately after addition of relaxin and 60 and 120 min later motility, progressive motility, mean path velocity, mean progressive velocity, mean linearity and mean lateral head displacement were measured with the Hamilton-Thorn motility analyser. Neither immediately after relaxin addition, nor after 60 or 120 min, was an improvement of sperm motility observed at any concentration.

Active immunization with relaxin does not influence objectively determined sperm motility characteristics in rabbits

Two groups of 5 rabbits were actively immunized with porcine relaxin or sham immunized. Serial analysis of sperm motion characteristics using the computer assisted Hamilton-Thorn Motility Analyzer over a period of 22 weeks did not reveal any significant antibody titers in serum and seminal plasma. In consideration of the present findings and after critical review of the literature it is concluded that an influence of relaxin on sperm motility is unlikely.

Comparison of motility stimulants for cryopreserved human semen

Caffeine, pentoxifylline, 2-deoxyadenosine, cyclic adenosine monophosphate (cAMP), relaxin, adenosine, kallikrein, and calcium were compared for their ability to stimulate motility of cryopreserved sperm. Caffeine, pentoxifylline, and 2-deoxyadenosine significantly increased the percentage of motile sperm at 15, 30, 45, and 60 minutes after administration. Sperm velocity was significantly increased by caffeine at 0, 15, 30, and 45 minutes, and by pentoxifylline at 0, 45, and 60 minutes. Consistent stimulation was not observed for other chemicals. Caffeine, pentoxifylline, and 2-deoxyadenosine were then examined for their ability to provide motility stimulation after removal with washing. With the exception of caffeine, percent motility and velocity for stimulated and untreated sperm were similar after washing. A significant reduction in motility was observed at 48 hours after washing for caffeine. The percentage of hamster oocytes penetrated at 24 hours after washing was significantly reduced for caffeine, 2-deoxyadenosine, and pentoxifylline combined with 2-deoxyadenosine. Pentoxifylline-treated sperm showed no reduction in fertilizing capacity. These results indicate that, of the chemicals examined, pentoxifylline is superior for motility stimulation of cryopreserved sperm.

Effects of relaxin on the fertilization capacity of human spermatozoa

Relaxin, a polypeptide hormone found in human seminal plasma, exerted favorable effects on the function of spermatozoa. This study was designed to investigate the effect of this hormone on the fertilization capacity of human spermatozoa from 10 oligospermic men (group A), 11 asthenospermic men (group B), 10 normospermic infertile men (group C), and 10 men with verified fertility (group D). We compared the effects of purified porcine relaxin at different concentrations (0, 50, and 150 ng/ml). Parameters include motility, hypoosmolar swelling test, and zona-free hamster egg penetration test. In group A and group B, relaxin increased the results of the hamster egg penetration test and motility. In group C, results of the hamster egg penetration test and motility improved only at the concentration of 50 ng/ml. In group D, relaxin increased the results of the hamster egg penetration test only at a concentration of 150 ng/ml. Results of the hypoosmolar swelling test were not consistently altered in any study group. Relaxin appears to enhance the fertilization capacity and motility of human spermatozoa in oligospermic and asthenospermic subjects.