Hormonal regulation of testicular human chorionic gonadotropin binding and steroidogenesis in adult mice with different forms of hereditary diabetes and obesity

The regulation of testicular hCG binding and steroidogenesis in adult mutant mice with hereditary diabetes and obesity was studied. Low doses of hCG caused no change in hCG binding in obese (ob/ob) mice, whereas, in diabetic (db/db) mice, the increase in binding measured 24 h after hCG administration was not as great as in normal males. Intermediate doses of hCG caused a decrease in hCG binding in obese and normal mice, but not in diabetic animals. However, 72 h after injection of intermediate doses of hCG, a decrease in hCG binding also was observed in diabetic mice. Plasma testosterone was elevated 24 h after hCG injection in all types of mice studied, but the increase in diabetic mice was smaller than in normal animals. However, 72 h after treatment with hCG, plasma testosterone was still elevated in diabetic mice, but not in normal males. In vitro, hCG stimulated testicular testosterone synthesis in all groups of mice, but the observed increase was smaller in diabetic and obese than in normal animals. Plasma LH levels were higher in diabetic than in normal mice, whereas plasma FSH and prolactin levels were lower in obese mice than in normal animals. All parameters (i.e., LH receptors and circulating hormone levels) measured in yellow (Ay/a) mice were similar to those in normal (a/a) mice. The present study indicates that in these models for noninsulin-dependent diabetes, the testicular metabolism of LH receptors and capacity to secrete steroids is altered.     

Temporal relationship of the prolactin-dependent LH-induced LH receptor to the LH stimulus

The time course for LH induction of luteinizing hormone (LH) receptors as reflected in binding of ¹²⁵l-labeled hCG was investigated in hypophysecto-mized adult male rats. A low dose of oLH (10 μg) was administered to hypophysectomized adult male rats following pretreatments with prolactin, follicle-stimulating hormone (FSH), growth hormone (GH), or saline. Testicular binding of hCG was determined at different times following the LH injection using Leydig cell membrane preparations from a testicular homogenate. Seven days after hypophysectomy, hCG binding was at a nadir of 19 ± 7% (mean ± SD) of control values. Pretreatment with prolactin (100 μg/day) for 7 days was associated with a nonsignificantly different hCG binding that was 30 ± 5% of control values. Prolactin pretreatment plus a single 10 μg LH i.p. injection increased ¹²⁵l hCG binding up to 56 ± 10% of control values within 30 minutes of the LH injection. Luteinizing hormone-induced hCG binding persisted at a high level (51 ± 4% of control values) for 2 hours but returned to hypophysectomized control levels 6 hours after the i.p. LH injection. Seven days pretreatment with FSH or GH at 100 μg/day plus 10-μg LH injections was also tested. Neither FSH nor GH had a statistically significant effect on hCG binding nor could they mimic the ability of prolactin to allow for LH induction of hCG binding in the hypophysectomized adult male rats. These studies suggest that the induction or “up-regulation” of Leydig cell hCG binding by ovine LH is rapid and specifically dependent upon pre-exposure to prolactin.     

The continuous presence of ewes in estrus in spring influences testicular volume,testicular echogenicity and testosterone concentration,but not LH pulsatility in rams

The continuous presence of active male small ruminants prevents seasonal anestrus in females, but evidence of the same mechanism operating from the females to the males is scarce. This study assessed the effects of the continuous presence of ewes in estrus in spring on ram sexual activity, testicular size and echogenicity, and LH and testosterone concentrations. On 1 March, 20 rams were assigned to two groups (n = 10 each): isolated (ISO) from other sheep, or stimulated (STI) by 12 ewes, which were separated from the rams by an openwork metal barrier, allowing contact between sexes. Each week, four ewes were induced into estrus by intravaginal sponges. Live weight, scrotal circumference, testicular width (TW) and length (TL) were recorded at the beginning and at the end of the experiment, and testicular volume (TV) was calculated; at the same time, testicular ultrasonography and color Doppler scanning were performed. Blood samples (March to May) were collected once per week for testosterone determinations, and at the end of the experiment, blood samples were collected for 6 h at 20-min intervals for LH analysis. Rams were exposed to four estrous ewes in a serving-capacity test. Scrotal circumference, TW and TL were higher in the STI than in the ISO rams (P < 0.05) in May, and TV was higher (P < 0.05) in the STI (391 ± 17 cm³) than in the ISO rams (354 ± 24 cm³). In ISO rams, the number of white pixels was higher (P < 0.01) in May (348 ± 74) than in March (94 ± 21) and differed significantly (P < 0.01) from that of the STI rams in May (160 ± 33). In ISO rams, the number of grey pixels was higher (P < 0.05) in May (107 ± 3) than it was in March (99 ± 1). Stimulated and ISO rams did not differ significantly in mean LH plasma concentrations (0.8 ± 0.5 v. 0.9 ± 0.4 ng/ml), LH pulses (2.1 ± 0.5 v. 2.2 ± 0.2) and amplitude (2.0 ± 0.4 v. 3.2 ± 0.7 ng/ml, respectively). Stimulated rams had significantly higher testosterone concentrations than ISO rams from April to the end of the experiment. Stimulated rams performed more (P < 0.05) mountings with intromission (3.0 ± 0.4) than did ISO rams (1.5 ± 0.5). In conclusion, after 3 months in the continuous presence of ewes in estrus in spring, rams had higher TV and some testicular echogenic parameters were modified than isolated rams. Although exposed rams also had higher levels of testosterone after 2 months in the presence of estrous ewes, their LH pulsatility at the end of the study was not modified.     

Interspecies differences in the effects of HCG on testicular function among rodents

Adult mice, rats and hamsters were injected with 0 or 0.3 IU hCG/g BW, 24 h before sacrifice. Basal LH receptor concentration was highest in rats and lowest in hamsters (rats greater than mice greater than hamsters). Injection of hCG caused LH receptor down-regulation in rats and mice, and up-regulation in hamsters. Basal plasma progesterone was highest in hamsters and lowest in rats (hamsters greater than mice greater than rats), however, hCG increased plasma progesterone levels in mice and rats, but not in hamsters. Mice had much higher plasma and testicular testosterone levels than other species, but hCG did not induce a relatively more dramatic increase in any species. When testes fragments were incubated with 0 or 12.5 mIU hCG/ml for 4 h, hCG increased media progesterone levels in rats and control mice, but not in hamsters and hCG-injected mice. Also, hCG elevated media testosterone levels in control but not in hCG-injected animals. Furthermore, addition of hCG in vitro partially prevented the elevation of media testosterone induced by in vivo hCG. The present results indicate that the mechanisms for the transduction of the gonadotropic signal by the Leydig cells are species-defined.     

Interspecies differences in testicular LH receptors and in vitro testosterone production among rodents

Testes from rats, mice and hamsters were incubated for 4 h with 0, 3.125 or 12.5 mIU hCG/ml. The LH receptor concentration in incubated testes of rats and mice was higher than that observed in hamsters. Testosterone levels in incubation media were significantly different among species (mice greater than rats greater than hamsters). During the incubation, hCG caused an increase in testosterone levels in all three species, but produced no significant changes in LH receptor concentration. Furthermore, a correlation between LH receptor concentration and testosterone only in hamsters is observed. The efficiency of the LH receptor-steroidogenesis interaction was estimated from the ratio of testosterone levels to receptor concentration under basal conditions and was found to differ among species (mice greater than hamster greater than rats). The levels of PGE and PGF in incubation media were higher in mice than in rats or hamsters, and hCG did not alter prostaglandin levels in any of the species. The present results indicate that acute in vitro hCG stimulation of testosterone synthesis does not involve appreciable changes in testicular LH receptor levels.     

Autoregulation of testicular luteinizing hormone receptors in hypogonadal (hpg/hpg) mice

The autoregulation of testicular luteinizing hormone (LH) receptors was studied in hypogonadal (hpg/hpg) and normal mice. The basal concentration of LH receptors was more than three-fold higher in hpg/hpg than in normal mice. After injection of hCG, hpg/hpg mice showed a decrease in LH receptor levels which was not observed in normal mice. Plasma testosterone was undetectable in hpg/hpg mice, even after treatment with a single dose of hCG. Plasma prolactin levels were higher in hpg/hpg than in normal mice. The increase in basal LH receptor levels is thought to be due to a compensatory mechanism in which elevated prolactin could play a role. The differences between hpg/hpg and normal mice in the autoregulation of LH receptors observed could be due to the hypersensitivity of the physiologically immature testis in hpg/hpg mice to the action of hCG, to gonadotropin deficiency, particularly during the earlier stages of development, or to a direct effect of the hpg locus on the metabolism of LH receptors.These studies were supported by NIH Grants HD 12642 and HD 12671 (AB) and Grant CA-24145 (WGB).     

Effects of photoperiod and hCG on the regulation of testicular LH/hCG receptors in Syrian hamsters (Mesocricetus auratus)

The regulation of testicular LH/hCG receptors was studied in Syrian (golden) hamsters with testicular atrophy induced by exposure to short photoperiod (5L:19D) and in gonadally active hamsters kept in a long photoperiod (14L:10D). By 24 h after injection of hCG, long-photoperiod hamsters showed a dose-related decrease in the number of testicular LH/hCG receptors. At 48 and 72 h, there was a recovery from this 'down-regulation'. The recovery was much faster than has been reported for the rat and mouse, and it resulted in elevation of testicular LH/hCG receptor concentrations above basal values. Hamsters with short photoperiod-induced testicular atrophy showed an increase in testicular LH/hCG receptors after injection of hCG, except for animals injected with a very high dose. The hCG-induced increase in testicular LH/hCG binding in these animals was associated with reappearance of testosterone responses to subsequent hCG stimulation. Response of testicular LH/hCG receptors to hCG in prepubertal hamsters resembled that measured in animals with short photoperiod-induced gonadal atrophy.     

Characterization and comparison of testicular LH/hCG receptors of rhesus monkeys (Macaca mulatta) and green monkeys (Cercopithecus aethiops)

Testicular luteinizing hormone (LH/hCG) receptors were characterized in seven green monkeys and compared with those of four rhesus monkeys. Testicular tissue showed high binding affinity for ¹²⁵I-hCG, (0.9–2.5 × 10⁹ M^?1, and 0.7–1.64 × 10⁹ M^?1 respectively, for green and rhesus monkeys) and low binding capacity (0.343–0.682 fmol/mg and 0.198–0.355 fmol/mg testicular homogenate, respectively). There was no difference in binding affinity between the two groups. Testicular LH/hCG receptors in both species bound human LH (hLH) and hCG but did not cross react with ovine LH (oLH). Rat testicular tissue showed similar high binding affinity (6.4 × 10⁹ M^?1) and low binding capacity (1.04 fmol/mg tissue homogenate) for ¹²⁵I-hCG. Rat LH/hCG receptors bound hLH, hCG, and oLH to a similar degree.     

Hormonal regulation of testicular prolactin receptors and testosterone synthesis in golden hamsters

A study was conducted with hypophysectomized hamsters to determine effects of administration of prolactin (PRL), luteinizing hormone (LH), and follicle-stimulating hormone (FSH)-alone or in combination-on testicular PRL receptors and in vitro testosterone production. Hormonal injections commenced the second day after hypophysectomy, and hamsters were killed on Day 5, approximately 13 h after the last hormonal injection. PRL receptor numbers were reduced by hypophysectomy, and PRL administration alone lessened the extent of this decrease. By themselves, neither LH nor FSH affected PRL receptors, but a combination of PRL + FSH + LH produced the greatest effect on these receptors. Receptor affinity was only modestly affected by any treatments. In vitro testosterone synthesis was measured after addition of 0, 2, 10, and 50 mIU of human chorionic gonadotropin (hCG) to incubations of testicular tissue. Neither PRL nor FSH by themselves in vivo affected basal or hCG-stimulated testosterone production. However, PRL + FSH increased (p less than 0.05) the magnitude of the in vitro testosterone response to hCG, as well as the sensitivity of that response (slope of the dose-response curve). LH alone increased both basal and hCG-stimulated testosterone production. PRL + LH provided no additional increase in the magnitude of the testosterone response, but increased (p less than 0.05) the sensitivity. PRL + FSH + LH in vivo provided for the greatest sensitivity of the testosterone response to hCG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interstrain differences in testicular responses to hCG: effects of a female exposition

It is known that among many animal species, including laboratory mice, a short-time exposition to a female causes activation of the pituitary-testicular axis in males, which then rapidly decreases. Effects of a prolonged female exposition on the testicular testosterone output in response to hCG injections were investigated in adult males of two inbred mice strains CBA/Lac and PT. The males of both genotypes kept with females for 5 days were injected subcutaneously with 10 IU of hCG 120 minutes before decapitation. Males of the same genotype and similar age keeping alone were served as control. The serum testosterone concentration and its testicular content were measured with immune-enzyme assay. It has been shown that the hCG increased the testosterone concentration and its testicular content in control males of both strains, but the testosterone output was expressed more significantly in PT males in comparison with CBA/Lac. The prolonged exposition of a female itself did not influence the testosterone output in males of both strains. However, it increased significantly the testicular response to hCG in PT strain. The data obtained suggest that a long-term exposition of a female could reinforce the testicular reactivity to hCG in genotype-dependent manner.     

Effects of nutritional supplements on testicular size and the secretion of LH and testosterone in Merino and Booroola rams

Six Booroola and six Merino rams were fed either a diet which maintained constant live weight or the same diet plus a supplement of high protein lupin grain for 15 weeks, and changes in live weight and testicular volume were measured. Serial blood samples taken for 24 h before the start and 9 weeks after the treatment began were assayed for plasma LH and testosterone and the resulting profiles were analysed for pulses of both hormones. Five weeks later, the animals were given two intravenous injections of 1 μg gonadotrophin-releasing hormone (GnRH) 1 h apart in order to measure pituitary gland responsiveness. A further week later the animals were injected intravenously with 500 μg human chorionic gonadotrophin (hCG) and the levels of testosterone were measured in samples taken after 1.5 h to estimate the testicular responsiveness.The nutritional supplement stimulated testicular growth in both genotypes, so that at the end of the treatment period the testes had increased significantly (P<0.01) in volume by 66% in the Merinos and by 63% in the Booroolas. The live weights also increased, but by relatively less (34% and 43% for supplemented Merinos and Booroolas). The rates of increase in both testicular size and live weight were similar for the two breeds. There were no significant effects of diet on the tonic secretion of LH or testosterone, or on responsiveness to GnRH or hCG.The intervals between LH pulses were significantly shorter (P<0.05) in Booroola rams than in Merino rams both before and after treatment (5.8 h vs. 11.6 h before treatment). The breed differences in LH secretion were mimicked by the testosterone profiles. In the Booroolas, five of the twelve LH profiles contained groups consisting of two to four individually identifiable pulses, each of which elicited a separate pulse of testosterone. A pulse group was observed in only one profile from the Merinos (P=0.06). There were no significant differences between the genotypes in any other parameter of LH or testosterone secretion, or in their responsiveness to GnRH or hCG.It was concluded that (i) nutritional supplements will stimulate testicular growth in both Merino rams and Booroola rams; (ii) the increase in testicular size does not appear to involve an increase in the responsiveness of the testis to LH; and (iii) there are both qualitative and quantitative differences between the genotypes in the patterns of secretion of LH and testosterone which may be associated with the differences in their fecundity.     

Inhibition of in vitro human chorionic gonadotropin-stimulated testosterone production in testis and of ovulation in the rat by charcoal-treated rat testicular extract

Previously, we described the presence of a factor obtained from a 105,000 X g supernatant of rat testis that was found to inhibit human chorionic gonadotropin (hCG) binding to gonadal receptors. In the present study, similarly prepared testicular extract was tested for its effects on in vitro hCG-stimulated testosterone production by isolated testis interstitial cells and for its effect on spontaneous ovulation in the rat. Incubation of interstitial cells with charcoal-treated extract significantly inhibited the steroidogenic response to hCG in a dose-related manner. This inhibition was also apparent after heating the extract for 10 min at 100 degrees C. Preincubation of the cells with charcoal-treated extract resulted in an inhibitory effect that was not readily reversed by subsequent addition of hCG, revealing an element of irreversibility in the mechanism of inhibition. A single i.p. injection of testicular extract given between 1430-1630 h of proestrus inhibited spontaneous ovulation in the rat. This effect was also observed after heating the extract for 10 min at 100 degrees C; in contrast, no significant effect was obtained with the injection of a similar dose of liver extract. Administration of 5 IU hCG after pretreatment with the testicular extract did not reverse the inhibitory effect on ovulation, indicating that this effect was probably not exerted at the hypothalamus-pituitary level. It is concluded that the aqueous testicular extract contains a factor able to antagonize the physiological events mediated by luteinizing hormone (LH)/hCG, and that this factor is consistent with the presence of an LH/hCG-binding inhibitory activity in rat testis.     

Differential effects of follicle-stimulating and luteinizing hormones on testosterone production by mouse testes

In adult mice, direct intratesticular injection of ovine follicle-stimulating hormone (o-FSH-13; AFP 2846-C, from NIAMDD, less than 1% LH contamination) at 10, 100 or 1000 ng significantly elevated concentrations of testosterone (T) within the testis. These effects were rapid, with peak values attained by 15 min, and transient, with return to values comparable to that in the contralateral, saline-injected testis within 90 min. Intratesticular injection of FSH (1 microgram) significantly increased testicular T levels in 15- and 60-day old mice. This contrasted with the effects of intratesticular administration of human chorionic gonadotropin (hCG), which stimulated T production significantly at 30 days of age through adulthood. In adult mice, the equivalent LH to the possible contamination in the FSH preparation (1 ng) had no effect. Intratesticular injection of 10 ng LH produced comparable stimulation to that by 100 ng FSH (approximately 7-fold). Systemic pre-treatment with a charcoal-treated porcine follicular fluid (PFF) extract for 2 days reduced plasma FSH levels [86 +/- 17 (5) vs 700 +/- 8 (6); P less than 0.05], but had no effect on plasma LH. Twenty-four hours after the last treatment, the response to intratesticular injection of hCG (2.5 mIU), FSH (100 ng) or LH (10 ng) was also significantly attenuated in these mice. Intratesticular injection of PFF had no direct effect on testicular T levels. In vitro T production in the presence of hCG, LH or FSH were differentially affected by the concentrations of calcium (Ca2+) or magnesium (Mg2+) in the incubation media. The stimulatory effects of FSH were apparent at significantly lower levels of Ca2+ or Mg2+, than were those of LH or hCG. The results of these studies indicate that FSH is capable of stimulating testicular T production. Furthermore, the responsiveness to FSH is qualitatively different than that to LH/hCG in terms of the age pattern, as well as the dependence on Ca2+ or Mg2+. In addition, plasma FSH levels appear to influence testicular responsiveness to direct exogenous administration of gonadotropins. These studies indicate that FSH stimulation of T production can be differentiated from those of LH, and that these effects of FSH can be observed under physiological conditions.     

Effects of restraint stress on plasma LH and testosterone concentrations, Leydig cell LH/hCG receptors, and in vitro testicular steroidogenesis in adult rats

We examined the effect of restraint stress (3 hr) on plasma LH and testosterone levels, on the Leydig cell LH/hCG receptor, and on the activity of enzymes in the testicular steroidogenic pathway of the adult rat. Restraint stress caused a 47% reduction in plasma testosterone concentrations, but had no effect on plasma LH levels. The binding capacity and affinity of Leydig cell LH/hCG receptors were not affected by restraint. Stress did not affect the testicular activity of 20,22 desmolase or 3 beta-hydroxysteroid dehydrogenase, but testicular interstitial cells of stressed rats incubated in vitro with progesterone as a substrate produced more 17 alpha-hydroxyprogesterone but less testosterone than control cells, and when incubated with 17 alpha-hydroxypregnenolone, produced 39% less androstenedione and 40% less testosterone than control cells. These results suggest that restraint stress inhibited 17,20 desmolase but not 17 alpha-hydroxylase activity. When the delta 4 pathway was blocked with cyanoketone (3 beta-HSD inhibitor), stress did not alter the production of pregnenolone or 17 alpha-hydroxypregnenolone, but the production of dehydroepiandrosterone by cells from stressed rats was subnormal, suggesting again a reduction of 17,20 desmolase activity. The data suggest that a major site of the inhibitory action of restraint stress on testicular steroidogenesis is the 17,20 desmolase step. The disruption of androgen production by restraint appears to be LH independent since stress did not affect plasma LH levels, the binding capacity or affinity of LH/hCG receptors, or the activity of 20,22 desmolase.     

Paracrine effect of seminiferous tubule factors on rat Leydig cell testosterone production: Role of cytoskeleton

In Percoll purified Leydig cells from mature rat we have demonstrated that the basal testosterone production (9.5 ng/10⁶ Leydig cells/24 h) is increased 10-fold in presence of a saturating amount of hCG (1 IU/mL) and diminished in a dose-related manner when larger concentrations of gonadotropin are used to reach 14 ng/10⁶ Leydig cells for 50 IU of hCG. If 40% (v/v) seminiferous tubule medium (STM) is added together with hCG (1 IU/mL) to the incubation medium, a further increase (62%) of testosterone output is noticed. Obviously, when the testosterone production is low as a consequence of a higher dose of hCG (50 IU/mL), the STM (80%) improves the steroid synthesis five-fold (67.4 ng). Concerning the cytoskeletal components (microtubules, intermediate filaments and microfilaments) which have been examined in presence or absence of hCG and STM, we have found a rearrangement of cytoskeletal elements as well as cell-shape changes in relation with hormonal activity of the cells. The most prominent alterations of cytoskeletal elements have been observed after 24 h of incubation with 1 IU/mL of hCG added together with 80% of STM. The obtained results suggest that paracrine factor(s) presents in STM and acting in synergy with LH/hCG generate(s) the rearrangement of cytoskeletal structures which, in turn, facilitates the availability of cholesterol for the mitochondria and finally enhances the testosterone production in the rat Leydig cells.     

Reduction of testicular luteinizing hormone/human chorionic gonadotropin receptors by [D-Trp6]-luteinizing hormone releasing hormone in hypophysectomized rats.

Adult and immature male rats were hypophysectomized and injected daily with saline or 0.2 or 2 μg of superactive Luteinizing Hormone Releasing Hormone (LHRH) agonist, [D-Trp⁶]-LHRH subcutaneously for seven days - with, or without, concomitant treatment of 1 IU Human Chorionic Gonadotropin (hCG) or 50 IU Pregnant Mare Serum. The administration of [D-Trp⁶]-LHRH reduced Luteinizing Hormone/Human Chorionic Gonadotropin receptors in all cases. The magnitude of this reduction was dose-related. As small a dose as 0.2 μg of the peptide resulted in approximately a 72% reduction of the receptors. The results suggest a direct action of [D-Trp⁶]-LHRH on the testis. It also indicated that reduction of testicular Luteinizing Hormone/Human Chorionic Gonadotropin receptors by the peptide is not necessarily due to the over-stimulation of Luteinizing Hormone (LH) release from the pituitary through a “down regulation” mechanism.     

Seasonally and experimentally induced changes in testicular function of the Australian bush rat (Rattus fuscipes)

Serum concentrations of LH, FSH and testosterone were measured monthly throughout the year in male bush rats. Testicular size and ultrastructure, LH/hCG, FSH and oestradiol receptors and the response of the pituitary to LHRH were also recorded. LH and FSH rose in parallel with an increase in testicular size after the winter solstice with peak gonadotrophin levels in the spring (September). The subsequent fall in LH and FSH levels was associated with a rise in serum testosterone which reached peak levels during summer (December and January). In February serum testosterone levels and testicular size declined in parallel, while the pituitary response to an LHRH injection was maximal during late summer. The number of LH/hCG, FSH and oestradiol receptors per testis were all greatly reduced in the regressed testes when compared to active testes. In a controlled environment of decreased lighting (shortened photoperiod), temperature and food quality, the testes of sexually active adult males regressed at any time of the year, the resultant testicular morphology and endocrine status being identical to that of wild rats in the non-breeding season. Full testicular regression was achieved only when the photoperiod, temperature and food quality were changed: experiments in which only one or two of these factors were altered failed to produce complete sexual regression.     

Analysis of Pleiotropism at the Dominant White-Spotting (W) Locus of the House Mouse: A Description of Ten New W Alleles

Characterization of the pleiotropic effects of ten new putative W locus mutations, nine co-isogenic and one highly congenic with the C57BL/6J strain, reveals a wide variety of influences upon pigmentation, blood formation and gametogenesis. None of the putative alleles, each of which is closely linked to Ph, a gene 0.1 cM from W, gave evidence of complementation with W³⁹, a new allele previously shown to be allelic to W^v. All W*/W³⁹ genotypes resulted in black-eyed-white anemics with reduced gametogenic activity.¹ Homozygotes for seven of these mutations are lethal during perinatal life; anemic embryos have been identified in litters produced by intercross matings involving each of these alleles.—Phenotypes of mice of several mutant genotypes provide exceptions to the frequent observation that a double dose of dominant W alleles (e.g., W/W^v or W/W) results in defects of corresponding severity in each of the three affected tissues. One viable homozygote has little or no defect in blood formation, and another appears to have normal fertility. The phenotypes of these homozygotes support the conclusion that the three tissue defects are not dependent on each other for their appearance and probably do not result from a single physiological disturbance during the development of the embryo.—Although homozygosity for members of this series results in a wide range of phenotypes, the absence of complementation of any allele with W³⁹, the close proximity of each mutant to Ph, and the fact that all alleles produce detectable (though sometimes marginal) defects in the same tissues affected by W and W^v, support the hypothesis that each new mutant gene is a W allele.     

Effects of different numbers of ectopic pituitary transplants on regulation of testicular LH/hCG and prolactin receptors in the hamster (Mesocricetus auratus)

Adult male hamsters were given transplants of 1/2, 1, 2, 3 or 4 pituitaries under the kidney capsule and were killed 4 weeks later. Pituitary transplants produced a significant, dose-related increase in plasma prolactin levels, no changes in plasma LH and an increase in plasma FSH. Concentration of LH/hCG receptors in the testes was significantly increased in animals with 2 or 3 transplants and concentration of testicular prolactin receptors was significantly increased in those given 2 transplants. The apparent stimulatory effects of 1/2, 1 or 4 transplants on testicular LH/hCG and prolactin binding were not statistically significant. Some of the animals were injected with 0.3 i.u. hCG/g body weight 24 h before being killed. This produced a significant reduction in the levels of prolactin receptors and an apparent reduction in the levels of LH/hCG receptors in the testes. Elevation of plasma testosterone concentrations in response to hCG was significantly greater in animals given 3 or 4 pituitary transplants than in the remaining groups. These results provide further evidence that prolactin increases the number of LH/hCG and prolactin receptors in the hamster testis and suggest that changing the number of ectopic pituitary transplants may result in biphasic effects on the testis, with 2 or 3 transplants being maximally stimulatory.     

Serum levels of testosterone and gonadotrophins with respect to smoking status and genetic polymorphism of <Emphasis Type="Italic">GSTT1</Emphasis>

Objectives It is reported that parental exposure to toxicants can influence offspring sex ratio at birth. Studies have reported that several chemicals found in cigarette smoke are substrates of glutathione S-transferase T1 (GSTT1, a member of GSTθ). To determine the effect of cigarette smoke on serum levels of testosterone and gonadotrophins of smokers and possible association of these hormones levels with GSTT1 polymorphism, the present study was done. Methods Our study was conducted on 181 (40 smokers, 141 non-smokers) male subjects. Genomic DNA was extracted from peripheral blood. The GSTT1 genotyping was performed using PCR-based method. All measurements for testosterone, follicle stimulating hormone (FSH), and luteinizing hormone (LH) were done in one laboratory. Results In smoker subjects the mean ± sd of serum testosterone, FSH, and LH were 4.64 ± 1.63 ng/ml, 2.72 ± 1.17 IU/l, and 3.03 ± 1.04 IU/l, respectively. In non-smoker subjects the mean ± sd of serum testosterone, FSH, and LH were 4.49 ± 1.24 ng/ml, 2.89 ± 1.26 IU/l, and 3.07 ± 1.28 IU/l, respectively. There was no significant difference between smokers and non-smokers for serum testosterone (t = 0.622, df = 179, P = 0.535), FSH (t = −0.757, df = 179, P = 0.450), and LH (t = −0.179, df = 179, P = 0.858). Also there was no significant difference between smokers and non-smokers in either GSTT1 null or positive genotypes for levels of testosterone, FSH, and LH. Conclusion Based on present data, it might be concluded that serum levels of testosterone and gonadotrophins were not significantly different between smoker and non-smoker males in both null and present GSTT1 genotypes.