Plasma testosterone concentrations during postnatal development in the male common marmoset

Repeated measurements of plasma testosterone (T) were made in 56 male marmosets from the day of birth until 300 days of age and in 44 adults (greater than 3 years). The resulting profile of plasma T during postnatal development shows higher levels during infancy (1-90 days) followed by a nadir between 100 and 170 days and then a progressive rise in T during puberty. Although T levels of up to 21 ng/ml were measured in infant males, mean levels (+/- SEM) were 5.4 +/- 0.6 ng/ml (days 1-10), declining gradually to 1.7 +/- 0.1 ng/ml (days 100-110). No increase in mean T levels between 15 and 100 days was identified, and the onset of puberty was earlier in some males than measured previously in this species.     

Alterations in plasma concentrations of testosterone, LH, and prolactin associated with mating in the male rat.

The hormonal response of the male rat to sexual activity was investigated in two studies. In the first, no evidence of a chronic elevation in plasma levels of testosterone (T), LH, or prolactin (PRL) was observed in sexually experienced rats compared to naive controls. Both groups showed an acute increase in plasma levels of all three hormones following mating, but the increases shown by the experienced group were more pronounced. In the second study, plasma levels of T, LH and PRL rose in sexually experienced male rats following exposure to a mating arena whether it contained an estrous female, an anestrous female, or no other animal. However, the increases were considerably larger in the group exposed to estrous females. It is suggested that plasma hormones rise in anticipation of mating, although not to the same extent as following mating, and that the anticipatory rise may function to initiate or facilitate mating behavior.     

Daily and seasonal variations in plasma LH and testosterone concentrations in the adult male hedgehog (Erinaceus europaeus)

A double-antibody heterologous radioimmunoassay (RIA) was developed to measure plasma LH values in hedgehogs. This RIA system used anti-rat LH serum and rabbit LH (AFP-559B) for radioiodination and as standard. The accuracy of the method was evaluated and indicated the ability to detect various relative concentrations of LH in plasma. The minimum detectable dose was 0.2 ng/ml. The intra- and inter-assay coefficients of variation were 4.2 and 7.9% respectively. Biological tests, e.g. effect of castration, effect of castration + testosterone implant and GnRH administration, confirmed that this method was suitable to determine subsequent changes in pituitary gonadotrophic activity in the hedgehog. LH concentrations were determined in blood samples obtained during 1 year: (a) each month, at 4-h intervals during 24 h, from different groups of unanaesthetized animals fitted with a catheter and (b) twice a month, under a light anaesthesia, from the same group of 6 animals. During the year: (1) the range of LH change was narrow (minimum values congruent to 0.25 ng/ml and maximum values congruent to 2.00 ng/ml); (2) the 24-h LH patterns did not exhibit any daily rhythm; (3) a clear annual rhythm was observed with the highest values from February to April and the lowest values in October and November. LH decreased rapidly at the end of summer and increased progressively from December to February, during hibernation. In these experiments, it was not possible to determine the characteristics of LH release patterns in the hedgehog but individual profiles indicated clearly the episodic secretion of LH, particularly during the highest pituitary activity period. During the year, a close relationship between the seasonal cycles of plasma LH and testosterone was observed.     

Prenatal testosterone treatment alters LH and testosterone responsiveness to GnRH agonist in male sheep

Although evidence is accumulating that prenatal testosterone (T) compromises reproductive function in the female, the effects of excess T in utero on the postnatal development of male reproductive function has not been studied. The aim of this study was to assess the influence of prenatal T excess on age-related changes in pituitary and gonadal responsiveness to GnRH in the male sheep. We used the GnRH agonist, leuprolide (10 microg/kg), as a pharmacologic challenge at 5, 10, 20 and 30 weeks of age. These time points correspond to early and late juvenile periods and the prepubertal and postpubertal periods of sexual development, respectively. LH and T were measured in blood samples collected before and after GnRH agonist administration. The area under the response curve (AUC) of LH increased progressively in both controls and prenatal T-treated males from 5 to 20 weeks of age (P<0.01). The LH responses in prenatal T-treated males were lower at 20 and 30 weeks of age compared to controls (P<0.05). AUC-T increased progressively in control males from 5 through 30 weeks of age and prenatal T-treated males from 5 to 20 weeks of age. The T response in prenatal T-treated males was higher at 20 weeks compared to controls of same age but similar to controls and prenatal T-treated males at 30 weeks of age (P <0.05). Our findings suggest that prenatal T treatment advances the developmental trajectory of gonadal responsiveness to GnRH in male offspring.     

Altered androstenedione to testosterone ratios and LH concentrations during musth in the captive male Asian elephant (Elephas maximus)

Greater concentrations of androstenedione than testosterone were usually present during periods of non-musth in plasma collected weekly for various periods up to 2 years in 8 male Asian elephants (4-35 years of age). For the 6 males that exhibited musth the androstenedione/testosterone ratio shifted greatly in favour of testosterone. The severity of musth was assessed weekly using a scale of 1 to 5 for each of 8 behavioural traits including urine dribbling, temporal gland secretion and aggression. A significant correlation (P less than 0.05) was noted between plasma testosterone concentrations and the musth score value in 5 of 6 musth episodes. Brief shifts in the ratio of two androgens when testosterone predominated (n = 106) were seen during the non-musth period in 3 of the males studied continuously for 2 years. In 82% of these instances, stimuli of a sexual or aggressive nature had occurred in the preceding 48 h (chi 2, P less than 0.01). A heterologous bovine assay was used to measure LH values in plasma collected every 15 min for 12 h. Increases in testosterone concentrations followed pulsatile increases in plasma LH concentrations during 7 non-musth periods in 4 animals. Apart from pulse frequency, increases in the variables describing pulsatile LH secretion were seen in 2 strong musth and 2 mild musth episodes compared to non-musth values. A strong musth, however, was characterized by a much greater increase in pulsatile testosterone secretion than was a mild musth and which may be a function of the duration of musth.     

Plasma LH, FSH, testosterone, prolactin and androstenedione in male white-tailed deer after ACTH and dexamethasone administration

1. In order to investigate the role of the adrenocortical system in the regulation of plasma levels of reproductive hormones, adult male white-tailed deer (five intact and one castrated) from a captive herd were sedated with xylazine and ketamine and then challenged with various doses of ACTH with and without dexamethasone (DX) pretreatment. 2. Plasma levels of LH, testosterone (T), FSH, prolactin (PRL) and androstenedione (A) were determined by RIA in serial samples taken from the jugular vein. 3. An increase of A levels detected after ACTH in both intact and castrated deer indicated stimulation of secretion of adrenal androgens by ACTH. 4. No effect on FSH and PRL levels was observed in either group. 5. A significant decline of LH and T observed in various treatments could not be attributed to ACTH or DX administration. It is speculated that the decrease may be caused by anaesthetics which alleviate the stress induced in deer by the pre-immobilization activities.     

Plasma LH, FSH and testosterone concentrations in adult rams which were homozygous carriers or non-carriers of the Booroola fecundity gene

No gene-specific differences were found with respect to LH or testosterone pulsatile secretion (over 12 h), or in 12 hourly mean FSH concentrations in adult Booroola FF and ++ rams. Also, no differences between genotypes in the LH response to an injection of testosterone propionate, the FSH response to an infusion of bovine follicular fluid, or the testosterone response to injections of PMSG were noted. However, during the phase of seasonal testicular development, mean testosterone pulse amplitude (over 12 h) and the FSH response to 25 micrograms GnRH were higher in FF than in ++ rams (P less than 0.05); there were also significant effects of sire (P less than 0.05 in FF genotype only) and litter size (P less than 0.05) on testosterone pulse amplitude and GnRH-stimulated FSH release, respectively. During the breeding season, mean LH, but not FSH, concentrations were higher in FF than in ++ rams, after an injection of 0.5 micrograms GnRH; LH release was not affected by sire or litter size (P greater than 0.05). Long-term studies revealed that the FF rams were born in significantly larger litters, they weighed significantly less than ++ rams (P less than 0.05), and that bodyweight was significantly correlated (P less than 0.05) with litter size. There were no differences in testis size, and testis size was not significantly correlated with bodyweight. There was a strong tendency (P = 0.056) for overall mean FSH concentrations, measured weekly for 9 months, to be highest more often in FF than in ++ rams.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum FSH, LH and testosterone in the male rhesus following prostaglandin injection

Adult male rhesus were treated with PGE₂, PGF_2α or the 13,14-dihydro-15-keto metabolite of PGE₂ in a randomized crossover design. Serum concentrations of FSH, LH and testosterone were determined and compared to the respective values in the same uninjected animals. No significant changes were noted in controls or following the metabolite injection. FSH increased gradually for 4 hours after metabolite treatment. In contrast, injection of PGF_2α was followed by an abrupt (within 15 minutes) increase in LH and testosterone. FSH increased gradually in 2 of 3 treated animals. Injection of PGE₂ was followed by a similar abrupt increase in LH concentration. This was not always associated with a significant increase in testosterone or FSH. These results demonstrate that injections of PGE₂ or PGF_2α can change serum gonadotropin and testosterone concentrations in male rhesus monkeys, and that the effects of these two prostaglandins are qualitatively different.     

Plasma insulin-like peptide 3 and testosterone concentrations in male dogs: changes with age and effects of cryptorchidism

The objectives were to: (1) develop a time-resolved fluorescence immunoassay (TRFIA) to measure insulin-like peptide 3 (INSL3) in canine plasma; (2) investigate changes of plasma concentrations of INSL3 and testosterone with age in normal male dogs; and (3) compare hormonal concentrations among cryptorchid, normal, and castrated dogs to evaluate endocrine function of the Leydig cell component in retained testes. Blood samples were taken from normal male dogs from prepubertal age to advanced age (4 mo to 14 y, n = 89), and from unilateral cryptorchid (n = 31), bilateral cryptorchid (n = 7), and castrated dogs (n = 3). Canine plasma INSL3 was measured with a newly developed TRFIA. The minimum detection limit of the INSL3 assay was 0.02 ng/ml and the detection range was 0.02 to 20 ng/ml. Plasma INSL3 concentrations increased (P < 0.05) from prepubertal age (4-6 mo) to pubertal age (6-12 mo), and then declined (P < 0.05) from pubertal age to post-pubertal age (1-5 y), reaching a plateau. Plasma testosterone concentrations increased (P < 0.0001) dramatically from prepubertal to pubertal ages, and then seemed to plateau. Concentrations of both INSL3 and testosterone were lower (P < 0.0001 for each) in bilateral cryptorchid dogs than in normal and unilateral cryptorchid dogs. The INSL3 (range: 0.05-0.43 ng/ml) and testosterone (range: 0.10-0.94 ng/ml) concentrations were readily detected in bilateral cryptorchids, but not in castrated dogs (INSL3 < 0.02 ng/ml; testosterone < 0.04 ng/ml). In conclusion, plasma INSL3 concentrations in male dogs measured by a newly developed TRFIA had a transient surge at a pubertal age, whereas testosterone did not. Lower plasma concentrations of INSL3 and testosterone in bilateral cryptorchid dogs suggest impaired endocrine functions of Leydig cell component in paired retained testes. Therefore, peripheral plasma INSL3 and testosterone concentrations have potential diagnostic value in predicting the presence of bilaterally retained testes in male dogs.     

Plasma concentrations of testosterone,androstenedione, progesterone,oestradiol-17β, LH and FSH during the preovulatory period in the ewe

Seven mature ewes were synchronized to oestrus by two injections of 125 μg Cloprostenol given 9 days apart. Blood samples, collected for 72 h at 4-h intervals beginning 16 h after the second Cloprostenol injection, were assayed for testosterone, androstenedione, progesterone, oestradiol-17β, LH and FSH. For the testosterone measurements, two radioimmunoassays, using two different antisera, were validated and used. A typical pattern of release was observed for progesterone, oestradiol-17β, LH and FSH, with a preovulatory gonadotrophin peak recorded 16.1 ± 2.1 h after the observed oestrous behaviour. In two of the experimental animals, an extra oestradiol peak was recorded before the usual preovulatory rise. The changes in the concentrations of testosterone and androstenedione during the same period were not synchronous. The levels of the two androgens fluctuated considerably with occasional peaks of 150–250 pg/ml and even 900–1400 pg/ml. Although a tendency towards an increase in the levels of both androgens was observed during the period of oestrous behaviour, the individual variations were significant.     

Serum FSH, LH and testosterone in the male rhesus following prostaglandin injection.

Adult male rhesus were treated with PGE2, PGF2 alpha or the 13,14-dihydro-15-keto metabolite of PGE2 in a randomized crossover design. Serum concentrations of FSH, LH and testosterone were determined and compared to the respective values in the same uninjected animals. No significant changes were noted in controls or following the metabolite injection. FSH increased gradually for 4 hours after metabolite treatment. In contrast, injection of PGF2 alpha was followed by an abrupt (within 15 minutes) increase in LH and testosterone. FSH increased gradually in 2 of 3 treated animals. Injection of PGE2 was followed by a similar abrupt increase in LH concentration. This was not always associated with a significant increase in testosterone or FSH. These results demonstrate that injections of PGE2 or PGF2 alpha can change serum gonadotropin and testosterone concentrations in male rhesus monkeys, and that the effects of these two prostaglandins are qualitatively different.     

Plasma testosterone and 17 beta-estradiol concentrations, and aromatase activity, during courtship in male Triturus carnifex.

Plasma testosterone and 17 beta-estradiol were monitored during the main phases of male Triturus carnifex courtship. "Inactive" males showed higher levels of testosterone with respect to those found during the various courtship phases. Estradiol was low in "inactive" males, and it reached the highest values at the beginning of the courtship. In addition aromatase activity was higher in the brain of the newts at the beginning of the courtship. These findings seem to support the "aromatization hypothesis" in Triturus carnifex.     

Plasma testosterone and sexual behavior following intracerebral implantation of testosterone propionate in the castrated male rat

Interpretation of behavioral and other effects of intracranial steroid implants depends on knowledge of the rate of release of the implanted hormones into the general circulation. Testosterone propionate implants (200 μg, pellets) in the median eminence and pituitary were found to result in circulating levels of testosterone (T) twice as high as those in the anterior hypothalamus-preoptic area (AHPOA), posterior hypothalamus (PH), and cortex (Ctx). Implants in all cranial areas examined resulted in plasma T levels in the lower range of circulating T found in normal rats for the first 24 hr postoperatively, decreasing thereafter and reaching very low levels by the end of 2 weeks. There were no significant differences in the plasma T levels in rats with implants in the AHPOA, PH, and Ctx, but AHPOA implants were slightly more effective in restoration of sexual behavior than PH implants, and both of these implants were considerably more effective than those in the cortex. There was no apparent correlation between behavioral responses and peripheral levels of T. The major conclusion of this study was that the effects of hypothalamic implants of T on male sexual behavior cannot be explained by the presence of T in the peripheral circulation.     

LH secretion and testosterone concentrations are blunted after resistance exercise in men.

This study examined the hypothesis that exercise-induced changes in circulating testosterone would be centrally mediated via hypothalamic-pituitary release of luteinizing hormone (LH). We tested this hypothesis by examining overnight LH, total and free testosterone (TT and FT), and cortisol (C) concentrations in 10 young healthy men (21 +/- 1 yr) during two experimental sessions: a control and an acute heavy-resistance exercise bout (50 total sets consisting of squats, bench press, leg press, and latissimus dorsi pull-down). Exercise was performed from 1500 to 1700, and blood sampling began at 1700 and continued until 0600 the next morning. Blood was sampled every 10 min for LH and every hour for TT, FT, and C. Hormonal concentrations were determined via RIA, and the secretion characteristics of LH were analyzed with deconvolution analysis. When overnight postexercise concentrations were compared with control concentrations, no statistically significant (P < or = 0.05) differences were observed for LH half-life, LH pulse frequency, interpulse interval, pulse amplitude, or pulse mass. Significant differences were observed for LH production rate (13.6 +/- 4 and 17.9 +/- 5 IU. l distribution volume(-1) x day(-1) for exercise and control, respectively, a 24% reduction). For the ANOVA marginal main effect means due to condition, C was significantly elevated (5.9 +/- 0.7 vs. 4.0 +/- 0.4 microg/dl), while TT (464 +/- 23 vs. 529 +/- 32 ng/dl) and FT (15.6 +/- 0.7 vs. 18.3 +/- 0.9 pg/ml) were significantly decreased for the exercise condition. These data demonstrate that the decline in overnight testosterone concentrations after acute heavy-resistance exercise is accompanied by a blunted LH production rate and elevated C concentrations.     

Seasonal changes in inhibin activity in seminal plasma and serum concentrations of FSH, LH and testosterone in the male goat (Capra hircus)

Inhibin activity in goat seminal plasma was measured by in vitro assay throughout successive 9 months and its relationship with the serum FSH, LH and testosterone concentrations was investigated. Total inhibin activity (TIA) in seminal plasma gradually increased from spring to summer, reduced in autumn (P<0.05) and recovered toward winter (P<0.05). Serum FSH and LH reached a peak in mid-summer (P<0.01) and returned to the low levels in autumn. Serum testosterone also increased in mid-summer and kept the high levels until the early winter (P<0.05). Some positive correlation was found in monthly levels between seminal TIA and serum FSH (r=0.305; P<0.05). Results suggest that the summer increase of inhibin activity in seminal plasma relates with the mid-summer rise of serum FSH levels in the male goat.     

Plasma oxytocin concentrations during late pregnancy and parturition in the dog

While oxytocin is widely used in the treatment of dystocia in dogs, there is little information about its secretion before and during normal unassisted whelping. We therefore measured plasma oxytocin concentrations during late pregnancy and the expulsive stage of parturition. Blood samples were collected from eight dogs at 3-min intervals during a 42-min period between the 2nd and 14th day before whelping and during parturition after the birth of 1-3 pups. The litters consisted of 5-15 pups and the progression of the expulsive stage was linear and nearly parallel in the eight bitches. The overall mean (+/-S.D.) plasma oxytocin concentration during late pregnancy was 3.6+/-2.1pg/ml. Mean values in individual dogs ranged from 1.2 to 7.4 pg/ml, but the intra-animal variation was rather small. During the expulsive stage the overall mean (+/-S.D.) plasma oxytocin concentration was 12.9+/-13.9 pg/ml, with mean values in individual dogs ranging from 3.5 to 46 pg/ml. The mean area under the oxytocin curve for parturient dogs was significantly higher (P<0.05) than for pregnant dogs. During the expulsive stage, the peak plasma oxytocin level in individual dogs ranged between 10 and 117 pg/ml. In six of the eight dogs a pup was born during blood collection and in five of these animals the plasma oxytocin concentration increased temporarily during periods of abdominal straining and expulsion. However, straining efforts and expulsion were not consistently associated with a rise in the circulating oxytocin level. It is concluded that in the dog plasma oxytocin levels are higher and more variable during the expulsive stage of parturition than during late pregnancy. Interrelationships between the secretion pattern of oxytocin, the level of uterine contractility, and the progress of fetal expulsion in dogs need further exploration.     

Decreased fructose concentrations in coagulating glands of prepuberal rats treated with testosterone and LH

Doses of testosterone propionate from 2.5 to 320 microgram and doses of LH from 2 to 360 microgram given over 1--3 days generally decreased fructose/body weight ratios in the coagulating glands of late prepuberal rats. The ratios of testes, seminal vesicles, coagulating glands and ventral prostates to body weight were increased after different treatment regimes with testosterone propionate. These changes in the variables measured could be detected by computer analysis in spite of the rapid growth rates of organs of rats of this age. LH increased the weights of only the seminal vesicles and coagulating glands, and then, only at the highest doses given.