Participation of membrane sulfhydryl groups in the epididymal maturation of human and rabbit spermatozoa

Effect of Oral Zinc Supplementation on the Thiol Oxido-Reductive Index and Thiol-Related Enzymes in Seminal Plasma and Spermatozoa of Iraqi Asthenospermic Patients

A thiol group plays an essential role in sperm metabolism and the antioxidative defense state. Zinc is the second most abundant element in the human body, following iron. The present study was conducted to study the effect of zinc supplementation on the characteristics of semen along with thiol and thiol-related enzymes in semen of asthenospermic patients. Semen samples were obtained from 60 fertile and 60 asthenospermic men, from couples who had consulted the infertility clinic of Babil Hospital (Hillah city, Iraq). The subfertile group was treated with zinc; every participant took two 220 mg capsules of zinc sulfate per day for 3 months. Semen samples were obtained (before and after zinc supplementation). The levels of reduced thiol, oxidized thiol, thiol oxido-reductive index, and thiol-related enzymes activities were determined in spermatozoa and seminal plasma of patients and healthy groups. Oxidized thiol levels were significantly higher in the infertile patients compared to that in the fertile group. Conversely, reduced thiol level, sulfhydryl oxidase activity, and glutathione peroxidase activity significantly decreased in the infertile patients compared to that in the fertile group. Oxidized thiol levels, reduced thiol levels, and thiol-related enzymes activities of the infertile patients were restored to normal values after treatment with zinc. However, reduced and oxidized thiol levels in spermatozoa did not change significantly in the group treated with zinc. The quantitative values for RSH/RSSR and thiol-related enzymes may provide useful means to qualitatively express the oxidant/antioxidant balance in clinical and epidemiologic studies. ClinicalTrials.gov Identifier: NCT02985905.

Posttesticular development of spermatozoa of the tammar wallaby (Macropus eugenii)

Tammar wallaby spermatozoa undergo maturation during transit through the epididymis. This maturation differs from that seen in eutherian mammals because in addition to biochemical and functional maturation there are also major changes in morphology, in particular formation of the condensed acrosome and reorientation of the sperm head and tail. Of spermatozoa released from the testes, 83% had a large immature acrosome. By the time spermatozoa reached the proximal cauda epididymis 100% of sperm had condensed acrosomes. Similarly 86% of testicular spermatozoa had immature thumb tack or T shape head-tail orientation while only 2% retained this immature morphology in the corpus epididymis. This maturation is very similar to that reported for the common brush tail possum, Trichosurus vulpecula. However, morphological maturation occurred earlier in epididymal transit in the tammar wallaby. By the time spermatozoa had reached the proximal cauda epididymis no spermatozoa had an immature acrosome and thumbtack orientation. Associated with acrosomal maturation was an increase in acrosomal thiols and the formation of disulphides which presumably account for the unusual stability of the wallaby sperm acrosome. The development of motility and progressive motility of tammar wallaby spermatozoa is similar to that of other marsupials and eutherian mammals. Spermatozoa are immotile in the testes and the percentage of motile spermatozoa and the strength of their motility increases during epididymal transit. During passage through the caput and corpus epididymis, spermatozoa first became weakly motile in the proximal caput and then increasingly progressively motile through the corpus epididymis. Tammar wallaby spermatozoa collected from the proximal cauda epididymis had motility not different from ejaculated spermatozoa. Ultrastructural studies indicated that acrosomal condensation involved a complex infolding of the immature acrosome. At spermiation the acrosome of tammar wallaby spermatozoa was a relatively large flat or concave disc which projected laterally and anteriorly beyond the limits of the nucleus. During transit of the epididymal caput and proximal corpus the lateral projections folded inwards to form a cup like structure the sides of which eventually met and fused. The cavity produced by this fusion was lost as the acrosome condensed to its mature form as a small button-like structure contained within the depression on the anterior end of the nucleus. During this process the dorsal surface of the immature acrosome and its outer acrosomal membrane and overlying plasma membrane were engulfed into the acrosomal matrix. This means that the dorsal surface of the acrosomal region of the testicular tammar wallaby sperm head is a transient structure. The dorsal acrosomal surface of the mature spermatozoon appears ultrastructurally to be the relocated ventral surface of the acrosomal projections which previously extended out beyond the acrosomal depression on the dorsal surface of the nucleus of the immature spermatozoon.

Effect of heparin-reduced glutathione on hamster sperm DNA unpacking and nuclear swelling

This study examined the kinetics of sperm nuclear decondensation induced by the action of physiological concentrations of heparin and glutathione in hamster sperm nuclei as a chromatin model that contains protamine P1 and P2. Sperm suspension was incubated at different temperatures (37, 40, 43, and 46 degrees C) in media, keeping constant the concentration of either heparin or GSH and increasing concentrations of the other reagent. Spermatozoa nuclei without any treatment, incubated for 72 h, appear densely condensed. Swelling of hamster spermatozoa nuclei was observed after 30 min of incubation in the presence of efficient concentrations of heparin-GSH. The extent of this time lag was significantly reduced at higher temperatures. DNA presence was verified by the use of ethidium bromide, acridine orange, and Feulgen stain. Phase-contrast microscopy shows that nuclear decondensation begins at the equatorial levels, with DNA highly condensed at the acrosome pole, and the basal pole as the DNA attachment point. Electron microscopy observations showed that hamster sperm nuclei initiates its decompaction at the peripheral regions and this behavior remains until late stages of decondensation, nevertheless, the chromatin is organized into "hub-like" nuclear bodies that measured 10-100 nm in diameter, joined by a network of chromatin fibers with apparent reduction in number. At the decondensation full stage, the network seems to be wide open with a reduced number of hub-like nuclear bodies present in the interlace. DNA is not organized into topologically constrained loop domains and is attached to the basal plate instead of to the nuclear matrix or any other structure.

Presence and chemical composition of glycoproteic layer on human spermatozoa

Studies from electronic microscopy disclosed the presence of an electrodense stranded and branch-like electrodense layer that extends toward extracellular space. Chemical composition of this glycoproteic layer showed that protein and total sugar content is similar (0.98 microgram/microgram protein). As for the total sugar content of this glycoproteic constituent, sialic acid accounts for 40%, hexosamines 27%, and fucose 30%. Electrophoresis characterization of this constituent showed the presence of 6 different motility bands. Risen levels of sialic acid indicate the contribution of sialic residue in the net charge of the sperm membrane, its role during capacitation, and its possible participation in the formation of binding bridges between sperm membrane and ovum.

Maturation of hamster epididymal sperm motility and influence of the thiol status of hamster and rat spermatozoa on their motility patterns

A method for objective quantification of hamster sperm movement parameters as an indicator of maturation along the epididymis was established using a computerised system. Analysis of spermatozoa released into medium from five epididymal regions showed that the most drastic increases in percentage motility and curvilinear velocity (VCL) occurred from the distal corpus to the beginning of the proximal cauda and in straight-line velocity (VSL) from the beginning to a more distal site within the proximal cauda region. Both high osmolarity (400 mOsm/kg) and the thiol-oxidising agent diamide (10 microM) increased flagellar straightness of distal corpus spermatozoa, but VSL was increased only with the latter. The thiol-reducing agent dithiothreitol (DTT, 1mM) stimulated and maintained percentage motility and velocities of spermatozoa from the caput, stimulated only percentage motility of distal corpus sperm, but decreased velocities of those from the proximal cauda in prolonged incubation. In rats, diamide increased path straightness but not velocities of caput spermatozoa and yet caused immotility within 15 min, whereas DTT prolonged the maintenance of in vitro motility. The slight increases in kinematic parameters in the presence of DTT were enhanced by a 2-min preincubation with diamide. The finding that the effects of DTT and diamide were not compensatory suggests that the influence of the SH/S-S status on sperm movement is multifaceted, with decreasing sensitivity to stimulation upon sperm maturation.

Lipid changes of goat sperm plasma membrane during epididymal maturation

Highly purified plasma membranes of maturing goat caput-, corpus- and cauda-epididymal spermatozoa were isolated by aqueous two-phase polymer methods and their lipid constituents were analysed. Phospholipid (approx. 75% w/w), neutral lipid (approx. 15% w/w) and glycolipid (approx. 10% w/w) were the major sperm membrane lipids. There was a significant decrease in the total lipids (approx. 25% w/w), phospholipid (approx. 30% w/w) and glycolipid (approx. 80% w/w) contents of sperm membrane during epididymal maturation. On the contrary, the mature cauda-sperm membrane showed greater (approx. 50% w/w) neutral lipid content than that of the immature caput sperm. Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin were the phospholipids of the sperm membrane, the former two being the major lipids. Both PC and PE fractions consisted of three species--diacyl, alkylacyl and alkenylacyl forms, the last one being the dominant species in both PC and PE. Of all the phospholipids, diacyl PE decreased most strikingly (approx. 65% w/w) during sperm maturation. The neutral lipid fraction contained sterols, wax esters, 1-O-alkyl-2,3-diacylglycerol, triacylglycerol and fatty acids. Sterols represented nearly 75% w/w of the neutral lipids and cholesterol was the major component (approx. 95% w/w) of the sterol fraction. The sperm maturity was associated with marked increase of sterol (approx. 60% w/w) and steryl ester (approx. 200% w/w) and decrease (approx. 50-65% w/w) of the other membrane-bound neutral lipids. The glycolipid was identified as monogalactosyldiacylglycerol. The fatty acid profile of the various membrane lipids underwent marked alteration during the epididymal transit of the male gametes. Cholesterol/phospholipid and saturated/unsaturated fatty acid ratios increased greatly in the maturing sperm membrane. The altered lipid profile of the mature sperm membrane leads to changes in its fluidity that play an important role in determining the structure and functions of the biomembrane.

Biochemical parameters of initiation and regulation of sperm motility

Studies of in vitro models demonstrate that a forward motility protein (FMP) is required for the initiation of forward motility in the immature epididymal spermatozoa. FMP is a heat-stable glycoprotein derived from epididymal plasma. During the epididymal maturation of spermatozoa in vivo, there is a marked increase of intrasperm pH and level of cyclic adenosine monophosphate (cAMP). Several studies suggest that exogenous FMP in concert with elevated intrasperm pH and level of cAMP initiates flagellar motility during the epididymal transit of sperm. cAMP activates sperm cytosolic cAMP-dependent protein kinases, which in turn phosphorylate multiple intrasperm phosphoproteins that may regulate flagellar motility. Exogenous calcium ion activates intact sperm motility, although it inhibits motility of demembranated cells on reactivation. Occurrence of cAMP-dependent type I and II protein kinases, a novel cAMP-independent protein kinase, and a phosphoprotein phosphatase has been demonstrated on the external surface of spermatozoa. The sperm surface has a coupled-enzyme system: ecto-cAMP-independent protein kinase and phosphoprotein phosphatase that regulate the phosphorylation and dephosphorylation of endogenous sperm ectophosphoproteins. The specific activities of these ecto-enzymes increase markedly during forward progression, suggesting that they may have a role in regulating flagellar motility.

Ficoll gradient isolation of immature sperm of high purity and intactness from goat epididymis

An improved Ficoll density gradient centrifugation method has been described for the isolation of goat caput-epididymal immature spermatozoa of a high purity and intactness. The method consists of layering freshly extracted sperm suspension on the top of a Ficoll gradient comprising 2.5 ml each of 2%, 4%, 6%, and 8% Ficoll-400 in a modified Ringer's solution and centrifugation at 300 g for 3 min in a swing bucket table centrifuge. Spermatozoa, free from fat globules and blood cells, sedimented at the bottom of the 8% Ficoll layer. The plasma membrane of the isolated cells showed a high degree of intactness (approximately 96%) as assessed by lactic dehydrogenase marker enzyme and ethidium bromide-fluorescence methods.

Potentiation of ethyl methanesulfonate-induced germ cell mutagenesis and depression of glutathione in male reproductive tissues by 1,2-dibromoethane

EDB significantly depressed GSH in caput and cauda epididymis, but not in testis, 2 hours following injection. This depression was dose-related. EDB enhanced EMS-induced dominant lethal mutations at mating weeks 2 and 3 (of 6). At mating week 2 the fetal death rate was increased two-fold, while at week 3, the fetal death rate had increased to nearly three-fold greater than the EMS-only controls. Enhancement of fetal death rate was confined to postimplantation loss. As with EMS alone, the EDB potentiation of EMS-induced mutations was limited to postmeiotic stages of spermatogenesis. EDB also enhanced alkylation of rat spermatozoa by labeled EMS. Depression of GSH in reproductive tissues is correlated with a potentiation of dominant lethal mutations, as well as an increase in the binding of EMS to sperm heads.

Maturation antigen of the mouse sperm flagellum. I. Analysis of its secretion, association with sperm, and function

We report here recent findings on the sperm maturation antigen SMA4, which is secreted by holocrine cells of the distal caput epididymis and binds to the flagellar surface of mouse sperm during epididymal transit. Washed sperm from the caput and corpus epididymides of mice were examined by immunofluorescence and SDS-PAGE using wheat germ agglutinin, which binds specifically to SMA4 as a primary probe. Results indicate that sperm first exhibit WGA reactivity on their flagellae in the region of the distal caput, and that the appearance of WGA receptors is due to the binding of a 54-Kd glycoprotein (SMA4) to the cell surface. Extracts of epididymis containing SMA4 were tested for their ability to bind to the surfaces of caput and corpus sperm. Caput sperm surfaces bound SMA4 in a temperature-independent manner, and binding occurred in the presence of enzyme inhibitors, suggesting a nonenzymatic process. Biochemical studies revealed that SMA4 contains disulfide bonds which stabilize it on the sperm surface and restrict its mobility. Terminal carbohydrate residues of the molecule are sialic acids. The addition of SMA4 to caput sperm flagellae prevented tail-to-tail agglutination, normally seen when caput sperm are diluted into saline; and SMA4 was able to disperse clumps of agglutinated caput sperm. The data suggest that a primary function of SMA4 is to prevent tail-to-tail agglutination of sperm during storage in the epididymis.

Depression of glutathione in male reproductive tissues and potentiation of EMS-induced germ cell mutagenesis by L-buthionine sulfoximine

Buthionine sulfoximine (BSO) treatment significantly reduced testicular epididymal and vas deferens glutathione (GSH) levels in rats. Testicular levels of GSH were reduced by 20%, while epididymal GSH levels were reduced by more than 50%. BSO treatment correspondingly enhanced ethyl methanesulfonate (EMS)-induced dominant lethal mutations. EMS-induced resorption rates were doubled following BSO treatment. This effect was observed in mating wk 2 and 3 (d 8-19 following treatment), indicating effects on those germ cells which were in late testicular stages or were caput epididymal spermatozoa at the time of EMS treatment. The enhancement of the mutagenic action of EMS by BSO is restricted to the same time period (spermatid-spermatozoa transition, early epididymal maturation) as maximum sensitivity to the clastogenic action of EMS on male germ cells. The temporal pattern of EMS alkylation of rat spermatozoa correlated with the incidence of EMS-induced dominant lethal mutations. BSO depresses GSH in the male reproductive tract in a dose- and time-dependent manner. Perturbation of GSH in the male reproductive tract appears to influence chemical-induced germ cell mutations.

A simple quantitative method for the estimation of free ecto-sulfhydryl groups of spermatozoa

A simple rapid quantitative method has been developed for the estimation of sperm ecto-SH groups on the basis of their high affinity binding to the mercurial: [203Hg]p-chloromercuriphenylsulfonic acid (PCMPS) used as a surface probe. The thiol reagent did not penetrate the sperm plasma membrane, as evidenced by the extremely rapid time course of the binding reaction and undetectable uptake of [203Hg]PCMPS by intact goat spermatozoa. The binding reaction was not due to contaminating broken or damaged cells, if any. The method consists of incubating of highly motile goat spermatozoa with PCMPS in a modified Ringer solution at 37 degrees C for 5 min, agglutination of the labelled cells with polyethyleneimine (100 micrograms/ml) and filtration and washing of the cell suspension through Whatman No. 1 filter discs under mild vacuum. The binding interaction is proportional to cell concentration, specific and saturable at 50 microM PCMPS. The method is capable of estimating free ecto-SH as low as 25 pmoles. Spermatozoa possess 286 +/- 61 pmoles of free ecto-SH groups/10(6) cells. Scatchard analysis showed the presence in goat spermatozoa of multiple classes of ecto-SH groups differing in their affinity for PCMPS.

Occurrence of -SH containing molecules on the goat sperm external surface that are essential for flagellar motility

p-Chloromercuriphenylsulphonic acid (PCMPS), a thiol reagent which is believed not to enter the cells, strongly inhibits motility of freshly extracted goat cauda-epididymal sperm preparations containing epididymal plasma (EP). The inhibitory action of PCMPS is not due to its interaction with the -SH groups of the surrounding EP-proteins. Washed cells when pretreated with low concentration of PCMPS (25 microM) for a short period (6 min) lost motility completely when assayed in presence of EP. PCMPS-mediated inhibition of motility cannot be reversed with the addition of large excess of various-SH compounds. The data suggest that PCMPS binds with high affinity to the specific -SH group(s) of sperm ecto-sulfhydryl molecules to cause their inactivation irreversibly by altering their conformation and thereby destroys sperm motility.

Exchange of lipids between spermatozoa and seminal plasma in normal and pathological human semen

Normal and pathological semen were studied with regard to cholesterol and phospholipid content of sperm cells and seminal plasma. Spermatozoa from pathologic semen have similar concentrations of phospholipid-phosphorous and significantly higher cholesterol concentration than spermatozoa from normal semen. However, only oligoasthenospermic spermatozoa showed a significantly higher cholesterol/phospholipid ratio. Azoospermic seminal plasma showed the lowest values of both cholesterol and phospholipids, but the ratio of cholesterol to phospholipids was equal to that in normal spermatozoa. No significant difference was found in the cholesterol concentration of seminal plasma from oligoasthenospermic, asthenospermic, and normospermic subjects and only asthenospermic plasma showed a significantly lower concentration of this compound. Cholesterol and phospholipid exchange between sperm cells and seminal plasma was shown by the striking correlation between the lipid composition of seminal plasma with that of sperm cells.

Effect of prolactin on the calcium binding and/or transport of ejaculated and epididymal human spermatozoa

The prolactin concentration in human seminal plasma and in human epididymal cauda fluid was assessed by radioimmunoassay. The prolactin concentration in cauda plasma was found to be similar to that found in male blood serum (5.5 to 9.1 ng/ml) and significantly lower than the concentration of the hormone found in seminal plasma obtained either from euspermic (48 +/- 12 ng/ml) or from vasectomized volunteers (50 +/- 10.2 ng/ml) (P less than 0.001). Calcium binding and/or transport in ejaculated spermatozoa were found to be little (0.29 +/- 0.08 nmoles/10(8) cells) and dependent on a quickly saturable process. The addition of 200 ng of human prolactin/ml induced a 60% increase in this parameter, while 50 ng of prolactin/ml were ineffective. Epididymal human spermatozoa differ from ejaculated sperm cells in showing greater, time-dependent, calcium binding and/or transport under basal conditions (2.00 +/- 0.35 nmoles/10(8) cells/hour), and in being more susceptible to the stimulating action of prolactin (4.4 +/- 0.68 nmoles/10(8) cells/hour in the presence of 50 ng of prolactin/ml).