Plasma Androgen Concentrations Research Articles

Seasonal changes in luteinizing hormone-releasing hormone concentrations in microdissected brain regions of male rough-skinned newts ( Taricha granulosa)

Luteinizing hormone-releasing hormone (LHRH) concentrations were measured in specific brain areas of male rough-skinned newts collected from a single population throughout the reproductive cycle. Plasma androgen and corticosterone (B) concentrations were also measured. Androgen concentrations were highest during the breeding season (winter) and lowest during the summer. In contrast, plasma B was lowest during the breeding season and highest in the summer. Concentrations of LHRH in the infundibulum (I) and rostral hypothalamus (RH) were positively correlated throughout the reproductive cycle; LHRH was always higher in the I than in the RH. Concentrations of LHRH in the ventral preoptic area (POA) fluctuated independently of concentrations of LHRH in the I and RH. However, LHRH concentrations decreased to undetectable levels in all three brain areas in March and April, which was before the end of the breeding season and before plasma androgen concentrations had decreased. An injection of LHRH into postbreeding males resulted in a significant increase in plasma androgen concentrations, indicating that the pituitary-gonad axis was still functional at the end of the breeding season. These results support the hypothesis that an abrupt decline in LHRH secretion is the initial endocrine event that signals the end of the breeding season in this amphibian.

Stimulation of androgen and oestrogen concentrations in plasma of cows after administration of a synthetic glucocorticoid (flumethasone) at the end of gestation.

Administration of flumethasone (3.5 mg i.m.) to six cows on day 260 of pregnancy induced parturition in only one animal. In the other five cows circulating concentrations of epitestosterone and conjugated oestrogens increased to reach maximum values (epitestosterone, 13.73 +/- 2.81 nmol/l; conjugated oestrogens, 33.59 +/- 6.87 nmol/l) 2-3 days after treatment. Concentrations of these steroids were raised as long as the synthetic glucocorticoid was present in the circulation (as judged by depression of cortisol concentrations). After clearance of the drug, concentrations of these steroids declined to values present in the control group. Concentrations of unconjugated oestrogens were only slightly raised after flumethasone. In contrast to the effect observed after administration on day 260, treatment on day 270 induced parturition in four of six treated animals. In these cows, mean circulating concentrations of epitestosterone, unconjugated and conjugated oestrogens increased to 9.50 +/- 2.96, 9.62 +/- 1.48 and 36.51 +/- 4.8 nmol/l respectively to reach concentrations observed in the control group at parturition. After parturition the concentrations of epitestosterone and oestrogens declined rapidly in all groups.

A Study of the Role of the Postnatal Testes in Determining the Ontogeny of Gonadotropin Secretion in the Male Rhesus Monkey (Macaca mulatto)*

To further examine the role of the testes in determining the ontogeny of gonadotropin secretion in the male rhesus monkey, the time courses of circulating LH and FSH concentrations were determined using established RIAs in daytime and nighttime blood samples collected at weekly intervals from birth until 4 yr of age in intact animals (n = 7) and in males orchidectomized at approximately 1 week of age (n = 6). Estimates of plasma androgen (A) concentrations were obtained on nonchromatographed samples with a RIA that reacts with testosterone and other androgens. Plasma PRL concentrations were also determined by RIA, and body weight was monitored at weekly intervals. Testicular volumes were measured at weekly intervals after 1.8 yr of age in five animals. In intact animals, mean daytime plasma A concentrations during the first 3 months of infantile development ranged from 1-6 ng/ml. Daytime plasma A concentrations then declined to reach 0.5-1 ng/ml by 9 months of age, where they were maintained usually until 3 yr of age when circulating levels progressively increased to reach, by approximately 3.5 yr of age, mean levels (6 ng/ml) characteristic of fully mature males. During the transition from infantile to perpubertal development, circulating LH and FSH concentrations showed a pattern similar to that of A, with elevations during the first 2 months of life followed by a decline to undetectable concentrations. In contrast to A, however, distinct pubertal increments in circulating LH and FSH concentrations were not observed in daytime samples from intact animals. The first indication of the pubertal reactivation of the hypothalamic-pituitary-testicular axis was provided by a reemergence of nocturnal elevations in plasma A concentrations between 2-3 yr of age. These were followed shortly thereafter by detectable plasma LH concentrations in nighttime samples. Orchidectomy at 1 week of age resulted in a progressive and dramatic rise in circulating gonadotropin concentrations, which plateaued approximately 3 weeks later at values 1 order of magnitude greater than those observed in intact animals. This hypersecretion of LH and FSH was not sustained, however, and by 10 months of age, plasma gonadotropin concentrations in agonadal animals were indistinguishable from those in age-matched intact controls. These low levels of the gonadotropic hormones were maintained, in the absence of the testes, for approximately 2 yr until a second or "pubertal" postcastration hypersecretion of LH and FSH was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Plasma androgens and their association with the reproductive cycle of the male fence lizard, Sceloporus undulatus

1. 1. Seasonal variation in plasma androgen levels was determined for males of the lizard Sceloporus undulatus. 2. 2. Plasma androgens peaked in both spring and in fall prior to brumation, coinciding with periods of maximum testicular enlargement and advanced spermatogenic development. 3. 3. Plasma androgen concentrations were minimal during summer, following testicular regression and breeding in spring. 4. 4. Epididymal masses were positively correlated to plasma androgen levels, while abdominal fat body masses demonstrated a negative correlation.

Adrenal androgen concentrations in endometrium and plasma during the menstrual cycle.

Concentrations of 5-androstene-3 beta, 17 beta-diol (androstenediol), dehydroepiandrosterone (DHA) and DHA sulphate (DHAS) were measured in endometrium and plasma from normal premenopausal and perimenopausal women (average ages 37 and 48 years respectively) at different stages of the menstrual cycle. Plasma levels did not vary with the stage of the cycle for any of the three steroids. Mean plasma levels of androstenediol ranged between 2.03 and 2.92 nmol/l for premenopausal women and 1.38 and 1.58 nmol/l for perimenopausal women while mean concentrations of DHA were 20.80-36.41 nmol/l (premenopausal women) and 13.87-19.07 nmol/l (perimenopausal women). The values for DHAS were more variable and ranged between 3.20 and 4.56 and 2.94 and 4.25 mumol/l for pre- and perimenopausal women respectively. In premenopausal women endometrial tissue concentrations of androstenediol and DHA increased three to fourfold in the secretory phase while no increase was observed in DHAS. There was a similar increase in androstenediol but not DHA or DHAS during the secretory phase for perimenopausal women. A significant positive correlation was found for tissue androstenediol and DHA in both groups of women but the relationship between DHAS and the other androgens was significant only for perimenopausal women. We suggest that the increase in androstenediol and DHA concentrations could be due to an increase in a receptor or binding protein, possibly progesterone dependent, present in secretory phase endometrium.

Reproduction in the Male Dasyurid Antechinus minimus maritimus (Marsupialia: Dasyuridae)

Reproduction in male Antechinus minimus maritimus was investigated in the field and laboratory by morphological, histological and endocrinological techniques. All males died in late July or early August immediately after mating. Testicular weight was maximal in May and then declined abruptly in June. Spermatogenesis lasted from February to May. The germinal epithelia of some tubules at the time of testicular regression consisted of only Sertoli cells, while in others some spermatogonia were also present. Prostate and Cowper's glands were maximally enlarged in June and July, which coincided with the maximal concentration (5 ng ml-�) of androgens in the blood. During the rest of the year concentrhtions were less than l ng ml-�. It is concluded that reproduction in male A. m. maritimus is essentially the same as in other Antechinus which exhibit male 'die-off'. The low concentrations of plasma androgens during spermatogenesis in Antechinus indicate that if these steroids are important for spermatogenesis, only relatively small amounts are required.

Plasma oestradiol-17 beta and testosterone concentrations as possible causes of the infertility of congenitally obese Zucker rats.

The plasma oestradiol-17 beta concentrations of obese and non-obese female Zucker rats have been measured in three phases of the oestrous cycle. The oestradiol concentrations of both phenotypes were similar, and changed normally with the oestrous cycle. The weights of the uteri also changed normally with the cycle. Plasma androgen concentrations in male Zucker rats have also been measured: the mean concentration was slightly but significantly lower in obese rats, and androgen-sensitive tissues were slightly reduced in weight. The oestradiol-17 beta concentrations in males of both phenotypes were similar. It seems unlikely that deficient plasma concentrations of gonadal hormones cause the infertility of obese rats of either sex.

Zmienność sezonowa w koncentracji androgenów w osoczu krwi jelenia szlachetnego

Plasma androgen concentration was measured in 3 red deer stags by radioimmunoassay monthly during 2 or 3 years. The seasonal changes in androgen concentration was correlated with the reproduction and antler cycles. The highest values from 14 to 36 ng/ml were found in September and the lowest ones from 0.2 to 1.5 ng/ml in April and May.

Aminoglutethimide stimulates extra adrenal δ-4-androstenedione production

The source of androgens was investigated in dogs (mean weight 17.9 kg) during aminoglutethimide (AG) adrenal blockade because it has been found that AG treated postmenopausal patients maintain androgen concentrations in plasma while estrogens are suppressed. Treatment started 2 days following bilateral oophorectomy (sterile conditions). Group 1 ( N = 5) received no drug, Group 2 ( N = 5) received AG (20 mg/kg b.i.d. × 7 days, 10 mg/kg b.i.d. × 7 days), and Group 3 ( N = 5) received AG plus Cortisol 0.5 mg/kg/day. At a second laparotomy (Na pentobarbital 35 mg/kg iv, 98% O 2/2% CO 2 controlled volume ventilation, anticoagulation, Na heparin), aortic and venous monitoring catheters and a left adrenal vein to femoral vein T-shaped silastic catheter for total left adrenal vein blood flow diversion were inserted. Five adrenal vein flow determinations with simultaneous aortic and adrenal vein blood samplings occurred over an hour. Radioimmunoassay (cortisol, 17-OH-progesterone and δ-4-androstenedione [D-4-A]) of pooled aortic and adrenal plasma of each dog with flow values allowed mean adrenal secretion rate calculations for each steroid determined. Treatments suppressed adrenal secretion of D-4-A ( P ⩽ 0.004) (Group 1: 24,000 pg/min ± 11,300 (1 SD); Group 2: 5300 ± 1299; Group 3: 9800 ± 5100), but aortic concentrations of D-4-A were comparable (Group 1: 116 pg/ml ± 27; Group 2: 114 ± 70; Group 3: 92 ± 73) in observed and treated groups (analysis of variance). Linear regression correlation of adrenal D-4-A secretion to aortic concentration ( r = 0.89, P ⩽ 0.04) in controls was absent in treated groups. Insignificant suppression of adrenal secretion of cortisol and 17-OH progesterone corresponds to the low AG dose required to avoid lethal obtundation in treated groups. AG treatment depressed the linear regression correlation of adrenal secretion to aortic concentrations of 17-OH progesterone. The results indicate a peripheral source of D-4-A. It can be hypothesized that AG induces hepatic enzymes of steroidogenesis for δ-4-androstenedione.

Steroid hormones in the blood plasma of Townsend's vole (Microtus townsendii)

Measurements of the concentrations of total corticosterone, corticosteroid-binding globulin (CGB), and total androgen in the plasma of male and female Microtus townsendii were made on two occasions separated by 13 days during a spring decline in numbers. The females had a much higher (7- to 12-fold) total and free corticosterone concentrations in their plasma than the males. Also, with the single exception of a female with no evidence of preceding pregnancy, which had a very low plasma androgen concentration, the concentration of steroids, resembling testosterone and dihydrotestosterone, in the plasma of the females was about double that in males with capture weights less than 80 g. Males, both wild and captive, with body weights in excess of 80 g at some time had plasma androgen concentrations up to fourfold those of the smaller males. Castration of males had no effect on total corticosterone or CBG concentration of the plasma. It is suggested that, at the time of sampling, the females were more readily stressed than the males and, hence, were at risk from the deleterious effects of excessive adrenocortical activity. The males taken from the wild population probably represented displaced animals, rather than more reproductively successful resident males. The source of the high total androgen concentration in the plasma of the females could be a special zone in the adrenal cortex which is known to appear after the first pregnancy in female Microtus agrestis.

Growth, hormonal and metabolic response of post-pubertal entire male cattle to trenbolone acetate and hexoestrol

ABSTRACTThe response of post-pubertal entire male cattle (bulls) to implantation with trenbolone acetate and hexoestrol was studied in two experiments. In experiment 1, eight British Friesian bulls, weighing approximately 359 kg at the beginning of a 90-day experiment, were either sham-implanted or implanted with 45 mg hexoestrol, followed 21 days later with a further implantation of 300 mg trenbolone acetate. In experiment 2, 16 bulls (14 British Friesian and two Simmental < ♂ × (Hereford < 5 × Friesian ♀), weighing approximately 349 kg, were similarly untreated or implanted with 30 mg hexoestrol and 300 mg trenbolone acetate. Treatment with hexoestrol gave a small and non-significant increase in live-weight gain in both experiments. However, live-weight gain and efficiency of conversion of food into live-weight gain were significantly improved in both studies following implantation with trenbolone acetate (P < 0·05). Treated bulls had heavier carcasses and greater mean values for estimated carcass gain (P < 005 in experiment 2). Comparison of mean values for blood metabolites indicated significant differences in concentrations of plasma glucose, free fatty acids and cortisol, and serum total protein, growth hormone, insulin and prolactin. Mean values were significantly lower in treated animals for serum albumin in experiment 2 (P < 001) and for plasma urea in both experiments (P < 0·001; P < 0·05). Treatment with hexoestrol resulted in lower mean concentrations of plasma androgens. These were further reduced following treatment with trenbolone acetate (P < 0·01). The results suggest that the combination of trenbolone acetate plus hexoestrol may improve growth performance, by altering protein metabolism, in post-pubertal entire male cattle. The combination of trenbolone acetate plus hexoestrol appears to have more potent anabolic activity than the endogenous hormones of these animals.

Duration of androgen treatment modifies behavioral response to arginine vasotocin in Taricha granulosa

Five and eighteen days after surgery, injection of arginine 8-vasotocin (AVT) stimulated clasping behavior in castrated controls (unimplanted or cholesterol-implanted) but not in androgen-implanted, castrated newts ( Taricha granulosa). Conversely, AVT injected 33 days after castration increased the incidence of courtship behavior of androgen-implanted males, but not of unimplanted castrates. Plasma androgen concentration of androgen-implanted castrates (as determined by radioimmunoassay) was maintained at a level typical of intact males at the peak of the breeding season. Because the AVT-androgen interaction could occur at the level of the pituitary gland, castrated, androgen-implanted newts were hypophysectomized and injected with AVT. Hypophysectomy did not abolish the behavioral response to AVT.

Luteinizing hormone-releasing hormone involvement in the reproductive behavior of a male amphibian.

The present study demonstrates that an intracerebroventricular injection of luteinizing hormone-releasing hormone (LHRH) activates sexual behaviors and elevates the plasma androgen concentrations in rough-skinned newts (Taricha granulosa). The stimulatory effect of LHRH on male behavior may be a seasonal phenomenon, because LHRH stimulation of sexual behavior was only observed during the early part of the breeding season (November and December). When an active LHRH antagonist was injected into male newts, sexual behavior was suppressed. These studies indicate that endogenous LHRH is involved in regulating sexual behavior in this amphibian.

The Effect of Caponization and Dietary 17 α-Methyltestosterone on the Incidence of Leg Abnormalities in Turkeys

Six hundred and seventy-two male turkey toms were raised according to standard management procedures from 1 day to 3.5 weeks of age. At 3.5 weeks of age, the poults were equally distributed among four treatment groups. One group was subjected to surgical caponization and a second to sham operations. Of the two remaining groups, one served as a control while the other received feed containing 110 ppm of 17 α-methyltestosterone. All birds were maintained under identical environmental conditions until 20 weeks of age.Capons demonstrated a significantly higher incidence of leg abnormalities than controls or testosterone fed birds but did not differ significantly from the shams. These data correlated well with the levels of plasma androgen in that capons had significantly lower levels of plasma androgen than controls or testosterone fed turkeys, but concentrations did not differ significantly from shams. Plasma androgen concentrations or percentages of leg abnormalities were not different among shams, controls, or testosterone fed birds. Body weights, feed/gain ratios, mortality, and plasma corticosterone were similar for all four treatment groups.

Nature of the Clearance of Exogenous Testosterone and Progesterone in Ejaculated Bovine Semen

Plasma and semen concentrations of androgens and progestins were not influenced by repetitive ejaculation in bulls. Within 20 minutes after the injection of testosterone (100 mg Intravenously), plasma concentration of androgen (mean ± SEM) was 698 ± 240 ng/ml (92% testosterone) and semen concentration of androgen was 27.7 ng/ml (76% testosterone). Within 20 minutes after the injection of progesterone (100 mg intravenously), plasma concentration of progestin was 2226 ± 635 ng/ml (96% progesterone) and semen concentration of progestin was 68.2 ± 2.2 ng/ml (68% progesterone). Thereafter, the concentrations of androgens and progestins in both plasma and semen steadily declined. Semen/blood concentration ratio values for progestins and androgens were similar to each other during the experimental period. It was concluded that testosterone and progesterone were readily transferred to the ejaculate from the blood.

Endocrine changes in dasyurid marsupials with differing mortality patterns

A comparison was made between the breeding-related endocrine changes in two species of dasyurid marsupial ( Antechinus swainsonii and A. flavipes), which exhibit a catastrophic male mortality after a brief mating period; and those of another dasyurid species ( Sminthopsis crassicaudata), the males of which survive an extended breeding period. In the males of both Antechinus species, the mating period was preceded by a rapid rinse in plasma androgen concentration and accompanied by a marked fall in plasma corticosteroid-binding globulin (CBG) concentration, to less than the total glucocorticoid concentration, which itself rose. As a consequence plasma free glucocorticoid concentration rose approximately 10-fold just before the males disappeared from the populations. Severe hemorrhagic ulceration of the upper digestive tract was consistently found soon after capture near the time of mating. In females, CBG concentration was always well in excess of total glucocorticoid concentration and free glucocorticoid concentration remained low. There was a significant negative correlation between plasma androgen and CBG concentrations in male Antechinus species from the natural populations. In laboratory-held castrate male A. swainsonii, injection of either testosterone or dihydrotestosterone caused a dose-related fall in CBG. In contrast to the above, the CBG concentration was always well in excess of total glucocorticoid concentration in the plasma of male S. crassicaudata and there was no evidence of interaction between plasma androgen and CBG concentration. These findings support the hypothesis that, in those species with a breeding-related mortality of males, an androgen-dependent fall in plasma CBG concentration and a stressful mating period result in death from adrenocortical suppression of the immune and inflammatory responses.

Relationship between antler development and plasma androgen concentrations in adult roe deer (Capreolus capreolus)

Four male deer (4-5 years old), living in normal park conditions, were captured every 2 weeks in the year to study annual variations in androgen levels and the relationship between testicular activity and the antler cycle. Data were also obtained from 77 wild adult males (greater than 3 years old) caught in the forest. Plasma androgen concentrations rose briefly in April and markedly in August; the high values in August corresponded with the breeding period. From the time of casting to maximum growth was about 60 days; mineralization of the antlers then lasted for 45 days only. The mineralization phase of antler growth corresponded to the reactivation of testicular function in late January (0.43 +/- 0.16 to 1.99 +/- 0.42 ng androgen/ml, N = 4).

Effect of intratesticular administration of gonadotropins on testicular and plasma androgen concentration in the lizard, Uromastix hardwicki

An acute effect of intratesticular injections of varying doses of ovine FSH (NIH-FSH-S12), ovine LH (NIH-LH-S20), and a lizard hypophyseal extract was observed on testicular and plasma androgen concentrations in Uromastix hardwicki. FSH and LH were used in a dose range of 0.25–4.00 ng and the hypophyseal extract was administered at concentrations representing 10–160 μg of fresh pituitary tissue obtained from adult male Uromastix. The test material was injected directly into one testis while the contralateral testis was likewise treated with an equal volume of saline. The control lizards received intratesticular injections of saline on both sides. Testicular and plasma androgen concentrations were measured 3 hr following the injections, using a specific RIA for testosterone. A significant increase in androgen concentration both in the testis and the plasma was obtained with 0.25 ng of FSH and 4.00 ng of LH. Both FSH and LH induced a significant rise in plasma androgen at 1.00 ng, but the increase was markedly greater in the FSH treated lizards. The homologous hypophyseal extract was shown to be active at the minimum dose level used (10 μg). The testosterone content of the uninjected testis in treated lizards was not significantly different from that of the control lizards. It is concluded that the intratesticular route of administration can be used as a sensitive and rapid method for studying in vivo responsiveness of the testis to mammalian and nonmammalian gonadotropins.

Concentrations of plasma luteinising hormone, prolactin, progesterone and androgens during the ovulatory cycle of the turkey.

1. Changes in the concentrations of plasma luteinising hormone (LH), prolactin, androgen and progesterone were measured during the ovulatory cycle of the turkey. 2. Single pre-ovulatory peaks of plasma LH, androgen an progesterone were observed which took 8, 8 and 12 h respectively, to increase and return to base-line values. The concentration of plasma prolactin tended to be elevated between 6 h before and 6 h after the LH peak with the maximum values occurring after the peak. 3. The changes in the concentrations of plasma LH and progesterone were 3- and 7-fold respectively while 2-fold changes were observed in the concentrations of plasma androgen and prolactin. 4. The pre-ovulatory concentration of plasma progesterone and prolactin began to decrease 4 and 6 h respectively, after the pre-ovulatory peak of LH. 5. Ovulation and oviposition occurred 6 to 8 h and 36.10 +/- 0.57 h (SEM) (n = 11) respectively after the pre-ovulatory peak of LH. 6. In birds kept on 14 h light/d, pre-ovulatory peaks of LH were initiated only during a 10 to 11-h period starting within 2 h after the onset of darkness. 7. A comparison between these data and those from the fowl suggest that the egg is retained in the turkey's oviduct for about 3 to 4 h longer than in the fowl.

Stress and mortality in a small marsupial (Antechinus stuartii, Macleay).

An investigation was made into the role of increased adrenocortical activity in the causation of the total postmating mortality of male Antechinus stuartii —a small shrew-like marsupial. A progressive rise in plasma androgen concentration of the males up to the time of mating was associated with increasingly aggressive behaviour and a progressive fall in plasma CBG concentration. During the mating period, the rate of fall in plasma CBG concentration increased markedly and plasma total corticosteroid concentration rose above the MCBC, so that there was a sharp rise in plasma free corticosteroid concentration just before the males all died. Although the plasma CBG concentration of females also fell during the mating period, with a moderate increase in plasma total glucocorticoid concentration, there was only a slight increase in plasma-free corticosteroid concentration at that time and it did not change significantly during the postmating, lactation period. Castration of captive males caused a marked increase in their plasma CBG concentration, and injection of testosterone or ACTH depressed it. There was a marked reduction in immunological competence and serum immunoglobulin concentration of the males just before their death. Postmortem examination revealed evidence of increased invasiveness of parasites and microorganisms, as well as severe haemorrhagic ulceration of the digestive tract. These effects could all be reproduced in captive animals by injection of cortisol acetate. It is concluded that a state of stress, induced by aggressive interactions at the time of mating and exacerbated by the fall in plasma CBG, results in suppression of the immune and inflammatory systems of the males, causing their death from gastrointestinal haemorrhage as well as invasion by parasites and microorganisms.