Binding of steroids to human spermatozoa and its possible role in contraception

Effect of endogenous hormones, antisperm antibody and oxidative stress on semen quality of crossbred bulls

The present study was designed to evaluate the effect of factors like hormones, antisperm antibody (ASA), and oxidative stress and its relation with semen quality in crossbred bulls. Ejaculates from two bulls were categorized into good (n = 12) and poor (n = 12) based on initial progressive motility, that is, ≥70% and ≤50%, respectively. The level of hormones like Testosterone (p < 0.05) and PGE₂ (p < 0.01) was significantly higher in good-quality ejaculates compared to poor-quality ejaculates; however, estradiol (p < 0.05), progesterone, oxidative stress, and ASAs were significantly higher (p < 0.01) in poor-quality ejaculates compared to good-quality ejaculates. Therefore, it could be concluded that oxidative stress and hormonal imbalance might have resulted in high number of dead and defective spermatozoa which was ultimately responsible for poor quality semen ejaculates.

Ginseng and male reproductive function

Ginseng is often referred to as the King of all herbs, and is found to be a promising agent to improve general well-being. Ginseng has also been reputed as an aphrodisiac, and is used to treat sexual dysfunction as well as to enhance sexual behavior in traditional Chinese medical practices. Data from animal studies have shown a positive correlation among ginseng, libido, and copulatory performances, and these effects have been confirmed in case-control studies in human. In addition, ginseng is found to improve the sperm quality and count of healthy individuals as well as patients with treatment-related infertility. These actions are mostly attributed to ginsenosides, the major pharmacological active components of ginseng. This review compiles the current knowledge about the multifaceted effects of ginseng on male reproductive function, and also focuses on its mechanisms of action that may represent novel therapeutic strategies for the treatment of male reproductive diseases or disorders.

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

OBJECTIVE

Norethisterone enanthate (NETE) is evaluated in trials of hormonal male contraception. It has been speculated that progestins may exert their contraceptive effects not only by suppressing gonadotropins but also by direct effects on male organs. NETE was given to monkeys in which endogenous gonadotropin secretion was suppressed by a gonadotropin releasing hormone (GnRH) antagonist, and replaced by human follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG). If NETE has a direct effect on spermatogenesis and/or epididymal function, some changes in testicular histology, sperm motility and/or morphology should occur soon after exposure to NETE.

METHODS

Fifteen adult intact male monkeys were grouped and treated for a 38-day period. Group I received GnRH antagonist, FSH, hCG and NETE while group II received a regime identical to group I without NETE and group III received only NETE and vehicle. Ejaculates, body weight, testicular biopsies and volume, and hormones were evaluated.

RESULTS

There was a similar pattern of serum FSH and testosterone in groups I and II. Testicular volume and the proportion of tubuli exhibiting spermatids was significantly decreased in group III. There were no significant differences between group I and group II in any parameters measured. The forward progression of sperm was not affected by NETE treatment. The consistently low percentages of grade c sperm indicated no sign of hyperactivation. No changes in the gross morphology of the acrosome were detected.

CONCLUSIONS

Short-term NETE treatment has neither a direct effect on the testis nor on the epididymis in this nonhuman primate model and its contraceptive effects appear to be exerted exclusively through gonadotropin suppression.

Rapid non-genomic actions of progesterone stimulate Ca2+ influx and the acrosome reaction in human sperm

This review summarizes some recent findings in human sperm which show that progesterone and 17 alpha hydroxyprogesterone are able rapidly (within seconds) to elevate [Ca2+]i and elicit the acrosome reaction (AR) via a non-genomic cell surface receptor. Progesterone promotes a transient elevation in [Ca2+]i which is blocked by extracellular La3+ and Ni2+ and removal of extracellular Ca2+ following chelation with EGTA. Some studies suggest that polyamines, trypsin-like proteases, and progesterone receptor aggregation are involved in progesterone-induced Ca2+ influx and AR. The receptor is not stimulated by the potent synthetic progestigins (e.g. promegestone, norethynodrel, megestrol acetate, cyproterone acetate) and is weakly antagonized by the genomic anti-progestins RU 486 and ZK 98.299. The sedative-hypnotic 3 alpha hydroxyl A-ring reduced pregnane steroids, which are powerful activators of the GABAA Cl- channel, are weak activators of Ca2+ influx and the AR. These data suggest that human sperm have a cell surface steroid receptor which is unlike the genomic progesterone receptor and the GABAA Cl- channel steroid receptor.

Selective expression of a progesterone receptor on the human sperm surface

OBJECTIVE

To visualize progesterone (P) binding sites on the sperm surface, examine the relationship between hormone binding and hormone action (acrosome reaction), and determine the size of the hormone-responsive sperm subpopulation.

DESIGN

Kinetic analysis of P binding was combined with the assessment of the hormone effect using a fluorescent acrosomal marker.

SETTING

Private hospital, medical research center, and a university-based andrological laboratory.

PATIENTS, PARTICIPANTS

Sperm samples were from healthy volunteers with normal spermiogram values.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Progesterone binding was analyzed by fluorescence microscopy and flow cytometry using P coupled to fluorescein isothiocyanate-labeled bovine serum albumin. Tetramethylrhodamine isothiocyanate-labeled Pisum sativum agglutinin was used as acrosomal marker in double-labeling experiments.

RESULTS

After in vitro capacitation, only few spermatozoa (approximately 10%) were able to bind P to the cell surface, but most of these cells subsequently generated the acrosome reaction in response to hormone binding.

CONCLUSIONS

The expression of P receptor sites on the human sperm surface is a major factor controlling the P-induced acrosome reaction. Further studies are warranted to explore if defective expression of the receptor can compromise fertility.

Mechanism of action of gestagens

In the mid-1950s it was shown that ovulation can be inhibited by oral administration of progesterone or of synthetic progestogens such as norethynodrel. The idea that progestogens may interfere with fertility even when administered in doses so small, that they do not invariably inhibit ovulation was launched in the mid-1960s by a group of Mexican investigators. Since then a large number of studies have been conducted on the mechanism of action of gestagens when used as contraceptives. The objective of this communication is to review the information collected so far on this topic.

Luteal phase sera and progesterone enhance sperm penetration in the hamster egg assay

The hormonal factors responsible for variation in sperm penetration rates of zona-free hamster ova caused by the use of human sera were investigated. Sera obtained at different times in the menstrual cycle, 17-beta estradiol (E2), or progesterone (P) was added to Biggers Whitten and Whittingham (BWW) medium used for the sperm penetration assay. Luteal phase sera enhanced egg penetration significantly when compared with either follicular or preovulatory sera (48.8% versus 23% and 25%; P less than 0.01). E2 at concentrations of 2 pg/ml to 2 X 10(6) pg/ml had no effect on sperm motility or egg penetration. Addition of P to control media at final concentrations of 0.5 to 50 ng/ml caused a significant elevation of egg penetration (68% to 91% to 96%; P less than 0.01) without affecting sperm motility. Since P has been shown to have a direct effect on plasma membranes and to bind to spermatozoan plasma membrane, the authors propose that P could have a physiologic role during capacitation or sperm egg interaction in vivo.

Effect of continuous local microdose norethisterone enanthate on the epididymis of adult rat

Unilateral implantation of a small silastic capsule containing crystalline Norethisterone Enanthate (NE, average observed rate of release, 17-22 micrograms/24 h) into the epididymal fat-pad of adult rats induced drastic impairment of epididymal functional anatomy in the adjacent epididymis six weeks later without affecting the contralateral epididymis. Tubular elements in the ipsilateral epididymis were highly shrunken with their luminal epithelial height greatly reduced and the lumen devoid of spermatozoa as compared with the normal epididymis (full of spermatozoa) on the sham operated contralateral side.

Partial characterization of human spermatozoal phosphodiesterase and adenylate cyclase and the effect of steroids on their activities

In sonicated human spermatozoa, phosphodiesterase hydrolyzed adenosine 3':5'-monophosphate (cAMP) at 20.80 +/- 3.23 nmoles/10(8)sperm/20 min at 37 degrees C (50 microM cAMP, initially). In human semen, about 60% of the phosphodiesterase activity was in the spermatozoa. Both polyacrylamide gel electrophoresis and DEAE-cellulose column chromatography indicated that there are at least 5 isozymes of phosphodiesterase. Various steroids were tested at a concentration of 2 micrograms/ml for their effects on phosphodiesterase activity in semen. None was found to have any significant effect. In sonicated human spermatozoa, adenylate cyclase synthesized cAMP at 0.02-2.11 nmoles/10(8)sperm/20 min at 37 degrees C (1 mM ATP, initially) depending on the availability of Mn2+ and caffeine in the assay mixture. Mn2+ was demonstrated to be a potent adenylate cyclase activator in human spermatozoa and its effect on human sperm adenylate cyclase was found to be dose-dependent. Cholera toxin, at a concentration of 20 micrograms/ml, had no effect on human sperm adenylate cyclase activity after it had been incubated with the intact spermatozoa for between 5 min and 5 h at 37 degrees C before the sperm were homogenized and the rate of cAMP formation assayed. In addition, human sperm adenylate cyclase decayed rapidly at 37 degrees C. Of various steroids tested at a concentration of 2 micrograms/ml for their effects on human sperm adenylate cyclase activity, only oestradiol-17 beta showed a significant effect, elevating the rate of cAMP formation by about 30%.

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

The location of steroid binding sites with specificity for oestradiol-17beta at an ultrastructural level has been examined on human spermatozoa by electron microscope autoradiography. About 75% of the 438 gains produced by 3H-oestradiol-17beta, and counted on electron microscope autoradiographs, were found over the plasma membrane or within 1000 A of it. This study provides evidence suggesting that the plasma membrane is a site of action of oestradiol-17beta in human spermatozoa.

The binding of sex steroids to human spermatozoa. An autoradiographic study

The locations of steroid binding sites with specificities for 17 beta-oestradiol, progesterone and testosterone have been examined on human spermatozoa by autoradiography. The binding sites were not evenly distributed over the entire surface of human spermatozoa. They were more densely located on the midpiece of the tail, less on the head and neck, and least on the principal- and end pieces of the tail. The binding sites for 17 beta-oestradiol were specific, with 3H-17 beta-oestradiol being displayed by unlabelled 17 beta-oestradiol, but less readily displaced by either progesterone or testosterone. The binding sites for testosterone were less specific than those for 17 beta-oestradiol or those for progesterone. Both 17 beta-oestradiol and progesterone were good competitors for testosterone binding sites, while the binding of 3H-progesterone was easily displaced by 17 beta-oestradiol, but less readily displayed by testosterone. Since there was preferential binding of these steroids to the mid-piece, and strong competition for binding between 17 beta-oestradiol and progesterone, these studies appear to provide information on the sites of action for the reported effects of these and related steroids on spermatozoal motility, migration and metabolism.

Activation of spermatozoal forward migration in vitro by hydrocortisone

The effects of hydrocortisone and cortisone on spermatozoal motility in vitro were tested Hydrocortisone at concentrations of 50, 100 and 1000 nmoles/ml was effective in activating in vitro the forward migration and the motility of boar spermatozoa recovered from the cauda epididymidis. Where boar epididymal spermatozoa were incubated with hydrocortisone at concentrations of 50, 100 and 1000 nmoles/ml for between 0 and 24 h at 25 degrees C in vitro, the spermatozoal motility was significantly higher than where no hydrocortisone was added. With ejaculated boar spermatozoa, hydrocortisone at concentrations of 100 and 1000 nmoles/ml increased the spermatozoal motility for between 0 and 2 h and at concentration of 50 nmoles/ml increased spermatozoal motility for between 2 and 24 hr at 25 degrees C in vitro. After 4 incubation, the effect of hydrocortisone at a concentration of 100 nmoles/ml on boar ejaculated sperm motility was not significantly different from the control. But, hydrocortisone at a concentration of 1000 nmoles/ml inhibited for forward migration of boar ejaculated sperm after it had been incubated with the sperm for 6 h. Cortisone, although structurally similar to hydrocortisone, had no significant effect in improving the motility of boar spermatozoa. Both hydrocortisone and cortisone had no demonstrable effect on the forward migration and the motility of human spermatozoa in vitro.

The effect of steroids on the in vitro migration of washed human spermatozoa in modified Tyrode's solution or in fasting human blood serum

In modified Tyrode's solution, 17 beta-estradiol at concentrations between 0.1 microgram/ml and 320 nmoles/ml was effective in increasing human spermatozoal forward migration. 17 alpha-Estradiol, although structurally similar to 17 beta-estradiol, had no effect on human spermatozoal motility. DL-Norgestrel at concentrations between 0.1 migrogram/ml and 320 nmoles/ml inhibited spermatozoal motility. These stimulatory and inhibitory effects were not observed when fasting human blood serum was used as a penetration medium in place of the modified Tyrode's solution. Also, the motility of spermatozoa suspended in fasting human blood serum was better than that of spermatozoa suspended in modified Tyrode's solution or in seminal plasma. These observations indicated that there is a component(s) of fasting human blood serum which increases spermatozoal motility and can counteract the activation or inhibition of spermatozoal motility by 17 beta-estradiol or DL-norgestrel at the concentrations used here.

The binding of sterol sulfates to hamster spermatozoa

Spermatozoa obtained from the cauda epididymidis possess twice the ability to take up sterol sulfates in vitro when compared to sermatozoa obtained from the caput. This would suggest that a modification of the membrane composition of the spermatozoa occurs during passage through the epididymis. Free sterols are taken up in a similar pattern. Radioautographic studies reveal that, for sterol sulfates, this uptake occurs selectively in the regions of the head and mid-piece of the spermatozoa whereas the free sterols are distributed evenly throughout the length of the spermatozoa. The binding of sterol sulfates to spermatozoa appears to involve sites that are unsaturable. The possibility exists that sterol sulfates, previously implicated in membrane stabilization, may play a similar role in spermatozoa.