The binding of oestradiol-17beta to human spermatozoa - an electron microscope autoradiographic study

Localization of estrogen receptor alpha and beta RNA in germinal and nongerminal epithelia of the channel catfish testis

The germinal epithelium of the anterior region of the channel catfish testis is the site of spermatogenesis, whereas the nongerminal epithelium of the posterior region (seminal vesicle) may play a role in the regulation of seminal fluid composition. The available information indicates that estrogens play a physiological role in the regulation of spermatogenesis and seminal fluid composition in vertebrates. However, the cellular distribution of estrogen receptor (ER) gene expression in the teleost testis is poorly understood. Therefore, the objective of this study was to determine the presence and cellular distribution of ERalpha and ERbeta transcripts in germinal and nongerminal epithelia of the mature testis of channel catfish. RT-PCR of whole-testis RNA extracts showed that ERalpha and ERbeta RNAs are present in the mature testis. In situ hybridization of histological sections of the germinal epithelium showed that primary spermatocytes contain little or no ERalpha or ERbeta RNA. However, both ER transcripts were present in secondary spermatocytes and spermatids and their levels were relatively high in mature sperm. The columnar epithelium of the seminal vesicle also contained ERalpha and ERbeta RNA. The ER RNAs in epithelial cells of the seminal vesicle were not evenly distributed throughout the cytoplasm but seemed to concentrate in their apical region, near the nucleus. In conclusion, ERalpha and ERbeta genes are coexpressed in germinal and nongerminal epithelia of the mature testis of channel catfish and seem to be developmentally regulated in spermatocytes. These observations are consistent with the concept that estrogens, via interaction with ERalpha and ERbeta, participate in the regulation of male gamete development and fertility.

A delta 4-3-keto pathway for testosterone synthesis in the human spermatozoa

The ability of human spermatozoa to metabolize pregnenolone to progesterone and progesterone to testosterone was assessed. Sonicated specimens of freshly ejaculated sperm from two groups of husbands (n = 6, age 32-38 years; n = 6, age 30-51 years) of infertile couples in the range of sperm concentration between 237.5 and 568.5, 100.1 and 248.8 millions per ejaculate, were separately incubated with [7n-3H]pregnenolone and [1,2,6,7,16,17-3H]progesterone. Using the classical reverse-isotope dilution technique the desired products [3H]progesterone and [3H]testosterone formed from the respective substrates were isolated and characterized, yielding 1.4 to 12.2% and 3.1 x 10(-2) to 2.0 x 10(-1)%. Such metabolites were not evident in the controls. The results indicate that the human spermatozoa contain the enzymes necessary for the transformation of pregnenolone to testosterone via the delta 4-3-keto route.

Characterization of a delta 5-3 beta-hydroxy pathway of testosterone synthesis in the human spermatozoa

Sonicated specimens of freshly ejaculated sperm from two groups of husbands (n = 6, age 32-38 years; n = 7, age 27-38 years) of infertile couples in the range of sperm concentration between 237.5 and 568.5; 131.1 and 256.7 millions per ejaculate were separately incubated with [7n-3H]pregnenolone and [1,2,6,7(-3)H]dehydroepiandrosterone. Using the reverse-isotope dilution technique [3H]dehydroepiandrosterone and [3H]testosterone formed from the respective substrates were isolated and characterized, yielding 1.2 x 10(-2) to 4.6 x 10(-20/0) and 7.1 x 10(-2) to 2.5 x 10(-10/0)/ Such metabolites were not evident in the controls. These results provide evidence for metabolic transformation of pregnenolone to testosterone via the delta 5-3 beta-hydroxy route.

Diverse modes of action of progesterone and its metabolites

Progesterone and its metabolites have a variety of diverse effects in the brain, uterus, smooth muscle, sperm and the oocyte. The effects include changes in electrophysiological excitability, induction of anesthesia, regulation of gonadotropin secretion, regulation of estrogen receptors, modulation of uterine contractility and induction of acrosome reaction and oocyte maturation. The latency of the effects vary from several seconds to several hours. Thus, it is not surprising that multiple mechanisms of action are involved. The classical mechanism of steroid hormone action of intracellular receptor binding has been supplemented by the possibility of the steroid acting as a transcription factor after the binding of the receptor protein to DNA. Other mechanisms include influence of the steroids on membrane fluidity and acting through other cell signalling systems, membrane receptors and GABA(A) receptors. Of particular interest are multiple mechanisms for the same types of action. For example the effect of progesterone on gonadotropin release is largely exerted via the classical intracellular receptor as well as membrane receptors, whereas 3(alpha),5(alpha)-tetrahydroprogesterone-induced LH release occurs via the GABA(A) receptor system. The inhibition of uterine contractility by progesterone is regulated by progesterone receptors while the action of 3(alpha),5(alpha)-tetrahydroprogesterone on uterine contractility is regulated by GABA(A) receptors. The regulation of the differences in the pattern of progesterone effects on estrogen receptor dynamics in the anterior pituitary and the uterus in the same animal are also of considerable interest.

Emerging diversities in the mechanism of action of steroid hormones

The classical genomic action of steroid hormones acting through intracellular receptors is well recognized. Within this concept of action, questions regarding the ultimate fate of the hormone and lack of a tight correlation between tissue uptake and biological activity with receptor binding remain unanswered. Evidence has accumulated that steroid hormones can exert non-classical action that is characterized by rapid effect of short duration. In most of these cases, the hormone effects occurs at the membrane level and is not associated with entry into the cell. The possible mechanisms for these non-classical actions are: (a) changes in membrane fluidity; (b) steroid hormone acting on receptors on plasma membranes; (c) steroid hormones regulating GABAA receptors on plasma membranes; and (d) activation of steroid receptors by factors such as EGF, IGF-1 and dopamine. Data have also been obtained indicating that receptor-mediated insertion of steroid hormones into DNA may take place with the steroid acting as a transcription factor. These new proposed mechanism of action of steroid hormones should not be viewed as a challenge to the classical mechanism. These diverse modes of action provide for an integrated action of hormones which may be rapid and of short duration or prolonged to address the physiological needs of the individual.

Concentrations of intracellular sex steroids in human spermatozoa

In an attempt to determine whether human spermatozoa contain steroid hormones, the immunoreactive levels of progesterone, testosterone, and estradiol-17 beta were measured in the extracts of sonicated specimens of sperm obtained as ejaculates from husbands of infertile couples (n = 67, age 26-44 years). In the range of sperm concentration between 3.0 and 869.6 million per ejaculate (143.2 +/- 13.6 mean +/- SEM), the concentrations were as follows: progesterone 127.3-6685.4 fmol/ml (1434.5 +/- 178.6), testosterone 98.3-2219.1 fmol/ml (611.6 +/- 49.0), and estradiol-17 beta 33.0-678.1 fmol/ml (206.9 +/- 19.7). Using Pearson's correlation coefficient, the steroid hormone levels correlated significantly with the total sperm number (p < .02). The spermatozoa contained small but measurable amounts of the sex steroids.

Seminal estrone, estrone sulfate, and estradiol-17 beta levels in fertile and infertile males

The seminal levels of estrone (E1), estrone sulphate (E1S), and estradiol-17 beta (E2) were measured simultaneously after a chromatographic step in the semen samples of 79 men, including fertile volunteers, vasectomized subjects, and patients with oligozoospermia and secretory azoospermia. E1S concentrations in seminal plasma were higher than in serum (with a semen/serum ratio of approximately 2). Seminal E1 and E1S levels in oligozoospermic subjects were significantly decreased compared to controls (p less than 0.02 and p less than 0.03, respectively). The seminal E1S concentration was significantly reduced in azoospermic patients (p less than 0.02) and to a greater extent in vasectomized subjects (p less than 0.001). As seminal E1S is likely to be mainly of testicular origin, the decreased seminal E1S levels in oligoazoospermia are an index of impaired testicular function.

Effect of steroid hormones and capacitation on membrane potential of human spermatozoa

The accumulation of the lipophilic cation radiolabeled triphenylmethylphosphonium (TPMP+) was utilized to determine the resting membrane potential across the plasma membrane (psi) on human sperm. Washed sperm were suspended and incubated in low-K+ and high-K+ medium and allowed to take up the cation to a steady state (that is, 20 min at 37 degrees C). The data were transformed according to concentration using the intracellular volume and with these values inserted in the Nernst equation we obtain psi. When the concentration of K+ was low in the medium, the psi was -69 +/- 2 mV, the psi was temperature- and pH-dependent. The sperm were incubated in the same conditions in the presence of testosterone, estradiol, and progesterone. The addition of these hormones induced the decrease in psi by about 29%, 32%, and 40%, respectively. On the other hand, capacitation of spermatozoa was induced by the addition of calcium and the ionophore A23187 and in these conditions the psi decreased 50%. The action of the hormones on sperm membrane was accompanied by some steroid-dependent structural modification promoting the psi decrease. This effect plays an important role in the capacitation, preparing it for sperm penetration in the ova.

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.

Interactions among motility, fertilizing ability, and testosterone binding on spermatozoa of bonnet monkey (Macaca radiata)

Fresh ejaculates of bonnet monkeys were separated into fractions rich with highly motile and sluggishly motile spermatozoa. The motility, ability to fertilize zona-free hamster eggs, and distribution of testosterone-binding sites on spermatozoa were assessed to determine the relation between these sperm functions. Two parameters of objective assessment of motility--velocity and degree of flagellar bending--were significantly correlated with the ability to form pronuclei in zona-free hamster eggs. Only spermatozoa with good motility could form pronuclei, which might be important for assessment of the fertilizing ability. The motility was directly related to the distribution of testosterone-binding sites; the fraction having mostly motile spermatozoa was distributed over the sperm surface. The technique is simple and may be used to evaluate semen of nonhuman primates.

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.

Morphology and X-ray microprobe analysis of spermatozoa from fertile and infertile men in in vitro fertilization

This paper reports differences observed in the elemental content of fertile and infertile human spermatozoa used in an in vitro fertilization (IVF) program. "Fertile" and "infertile" were designated by the successful penetration or failure to penetrate an oocyte in vitro. We report morphological and morphometric differences which, together with elemental changes, may be causes of infertility in apparently normal spermatozoa. There were significant differences (P less than 0.05) in sodium and chlorine concentrations between fertile and infertile samples and there was more chlorine than could be accounted for as sodium chloride. Many spermatozoa showed particles adhering to tails, with a higher incidence of "contamination" in the infertile spermatozoa. There were significant differences in both shapes of heads and lengths of tails between fertile and infertile spermatozoa.

The binding patterns of antisera to sex steroids and human gonadotropins on human and rhesus monkey spermatozoa

The presence of different hormones on the surface of ejaculated spermatozoa was determined by immunofluorescence studies of the binding patterns of specific antisera to these hormones. There were striking similarities in the binding pattern of antisera to steroid hormones found on human and monkey spermatozoa. Assuming the intensity of fluorescence is proportional to the concentration of the hormone, concentrations of testosterone on the acrosomal and the postacrosomal regions were higher than levels of progesterone and estrogens. Spermatozoa with a "tapering head" had more hCG bound on the acrosomal and postacrosomal regions than spermatozoa with "normal head" (oval shaped). Correlating these findings to the functions of spermatozoa will require further studies.

Effect of steroid hormones on membrane sugar transport in human spermatozoa

Using the model of exchange transport, we found that glucose transport through the human spermatozoa membrane (447 +/- 54 pmoles/min/10(8) cells) is probably the rate-limiting step in sugar utilization. Sugar transport was more efficient for glucose than for fructose (182 +/- 32 pmoles/min/10(8) cells) and depends on a highly asymmetric carrier with at least two transporting sites. Transport was drastically dependent on pH with an optimal pH of 7.4, showing a decrease of more than 60% with a change of 1 pH unit. Testosterone and 17-B estradiol increased the amount of transported sugar (619 +/- 73 and 922 +/- 110 pmoles/min/10(8) cells, respectively), while progesterone has no effect.

Stimulation of in vitro fertilization in mice with 17 beta-estradiol

The effect of various concentrations of estradiol on in vitro fertilization frequency was studied. Fertilization was stimulated by 5 X 10(-9) M 17 beta-estradiol but not by 5 X 10(-9) M 17 alpha-estradiol. At 5 X 10(-6), 5 X 10(-7), 5 X 10(-8), and 5 X 10(-10) M 17 beta-estradiol there was no difference in the fertilization frequency between test and control samples. It is suggested that stimulation of the acrosome reaction is instrumental in increasing the fertilization rate.

Steroid metabolism by monkey and human spermatozoa

Freshly ejaculated spermatozoa from monkey and human were washed and incubated with tritium labelled androgens or estradiol to study the pattern of spermatozoa steroid metabolism. When equal concentrations of steroid substrates were used for incubation, monkey and human spermatozoa showed very similar pattern of steroid conversion. Spermatozoa from both species converted testosterone mainly to androstenedione, but reverse conversion of androstenedione to testosterone was negligible. Estradiol-17 beta was converted mainly to estrone. The close similarity between the spermatozoa of monkey and men in their steroid metabolic pattern indicates that the rhesus monkey could be an useful animal model to study the effect of drugs on the metabolic pattern of human spermatozoa.

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

17 beta-Estradiol (E2) stimulated the zona-free hamster ova penetration by human spermatozoa from both fertile and subfertile men after 5 hours of incubation in vitro. For spermatozoa samples from fertile men, the mean penetration rates increased significantly (P less than 0.05), from 35.6% +/- 3.5% (control) to 60.1% +/- 5.8% (E2 = 50 ng/ ml) and 50.5% +/- 2.6% (E2 = 100 ng/ml), respectively. E2 also increased the mean penetration rates of spermatozoa samples from subfertile men significantly (P less than 0.05), from 10.2% +/- 1.8% (control) to 30.5% +/- 7.2% (E2 = 50 ng/ml) and 33.1% +/- 6.6% (E2 = 100 ng/ml), respectively. These findings indicate that E2 can affect the fertilizing ability of human spermatozoa in vitro.