Decrease In Plasma Testosterone Concentrations Research Articles

Photoperiodic control of singing behavior and reproductive physiology in male Fife fancy canaries

Temperate-zone birds display marked seasonal changes in reproductive behaviors and the underlying hormonal and neural mechanisms. These changes were extensively studied in canaries (Serinus canaria) but differ between strains. Fife fancy male canaries change their reproductive physiology in response to variations in day length but it remains unclear whether they become photorefractory (PR) when exposed to long days and what the consequences are for gonadal activity, singing behavior and the associated neural plasticity. Photosensitive (PS) male birds that had become reproductively competent (high song output, large testes) after being maintained on short days (SD, 8 L:16D) for 6 months were divided into two groups: control birds remained on SD (SD-PS group) and experimental birds were switched to long days (16 L:8D) and progressively developed photorefractoriness (LD-PR group). During the following 12 weeks, singing behavior (quantitatively analyzed for 3 × 2 hours every week) and gonadal size (repeatedly measured by CT X-ray scans) remained similar in both groups but there was an increase in plasma testosterone and trill numbers in the LD-PR group. Day length was then decreased back to 8 L:16D for LD-PR birds, which immediately induced a cessation of song, a decrease in plasma testosterone concentration, in the volume of song control nuclei (HVC, RA and Area X), in HVC neurogenesis and in aromatase expression in the medial preoptic area. These data demonstrate that Fife fancy canaries readily respond to changes in photoperiod and display a pattern of photorefractoriness following exposure to long days that is associated with marked changes in brain and behavior.

Exposure to low doses of malathion during juvenile and peripubertal periods impairs testicular and sperm parameters in rats: Role of oxidative stress and testosterone

Malathion is an organophosphate insecticide used in agriculture and for controlling vector-borne diseases such as Zika. Humans can be exposed to malathion by means of ingestion of contaminated food. The juvenile and peripubertal periods are a large window of vulnerability to the action of toxic agents. The aim of the present study was to evaluate the effects of low doses of malathion during the development of testes in the juvenile and peripubertal periods in rats. For this purpose, 45 male Wistar rats (postnatal day (PND) 25) were assigned to 3 experimental groups and treated for 40 days. The animals were exposed daily to malathion 10 mg/kg (M10 group) or 50 mg/kg (M50 group) diluted in 0.9 % saline via gavage. The control group received only the vehicle. On the 40th experimental day, the rats were anaesthetized and euthanized. The blood was collected for determination of testosterone concentration. The testes were removed and weighed. Spermatozoa from the vas deferens were used for sperm morphological analysis. The testes were used for evaluation of sperm count and oxidative stress status to determine the inflammatory profile and analysis of tissue constitution. The results showed that both malathion doses reduced the sperm count and increased the number of abnormal sperms. Furthermore, both doses altered the spermatogenetic process, delayed spermiogenesis, reduced the Leydig and Sertoli cell number and increased the thickness of tunica albuginea. The M10 group presented increased IL-10 levels and reduced GSH levels. These parameters did not change in the M50 group. However, the M50 group showed an increase in the number of abnormal seminiferous tubules, a decrease in plasma testosterone concentration and an increase in lipid peroxidation in the testes. In conclusion, the exposure to low doses of malathion during juvenile and peripubertal development resulted in testicular toxicity and compromised the testicular morphology and function.

Amelioration of testicular damages in renal ischemia/reperfusion by berberine: An experimental study.

BackgroundIschemic acute kidney injury is associated with an inflammatory reaction.Objective In the current study, berberine was assessed for its effect on the functional disorders and histological damages of testis induced by renal ischemia/reperfusion (I/R).Materials and Methods Twenty-eight adult male Wistar rats (260-300 gr) were equally divided into four groups (n = 7/each): sham and I/R groups which received distilled water as well as berberine (BBR) and BBR + I/R groups which received berberine (15 mg/kg/day) orally seven days before the surgery. In both groups of sham and BBR, renal arteries were not clamped. Renal I/R was induced by occluding right and left renal artery for 45 min followed by a 24 hr reperfusion period. Blood samples were taken for determining the plasma levels of creatinine, urea nitrogen, FSH (follicle stimulating hormone), LH (luteinizing hormone), and testosterone. Then the rats were killed under deep anesthesia and the left testis was immediately isolated and preserved.ResultsThe renal I/R injury led to testicular histological damages accompanied with increased plasma levels of creatinine, urea nitrogen, LH, and FSH, as well decrease of plasma testosterone concentration at the end of 24 hr reperfusion (All p 0.001, except for FSH p 0.01). Berberine diminished histological damage to the testis and attenuated the increase in plasma creatinine, urea nitrogen, LH, FSH, and decrease in plasma testosterone concentration in the BBR + I/R group (All p 0.001).ConclusionThese results suggest that ischemic acute renal failure induces functional disorders and tissue damages in testis of rat, which was improved through the administration of berberine.

Validation of a radioimmunoassay for measuring testosterone concentrations in plasma samples of the subterranean rodent Ctenomys talarum: outstandingly elevated levels in the wild and the effect of captivity

We validated the Coat-a-Count radioimmunoassay (RIA) kit for measuring testosterone in plasma samples of the subterranean rodent Ctenomys talarum and evaluated testosterone levels in free-living and captive individuals. The performance of the assay was evaluated by the assessment of parallelism, accuracy and precision. Moreover, the high specificity of the assay antibody was confirmed by high-pressure liquid chromatography with ultraviolet detector, followed by electrospray ionization tandem mass spectrometry. Results indicated that plasma samples have to be treated with heat and diluted before the RIA for the optimization of the assay. Plasma testosterone concentrations in free-living animals were outstandingly elevated (up to 329 ng/mL), which are among the highest ever reported for mammals. On the other hand, captivity produced a 14-fold decrease in plasma testosterone concentrations, emphasizing that very significant changes in the endocrine milieu may occur in wild animals kept under laboratory conditions. Our results place tuco-tucos as an interesting model for the study of androgen regulation in mammals, suggesting that target tissues may have low sensitivity to the testosterone signal and agree with a scenario of elevated levels of sex hormone-binding globulin in plasma.

Photoperiod and water temperature regulation of seasonal reproduction in male round stingrays ( Urobatis halleri)

This study characterizes the seasonal reproductive cycle of male round stingrays ( Urobatis halleri) in Seal Beach, California. Mature round stingrays were collected monthly by beach seine near the San Gabriel River outfall from August 2004–September 2006, and rays were assessed for gametogenesis and steroid hormone levels. Male round stingrays exhibit a seasonal pattern of increased gonadosomatic index (GSI), spermatogenesis, and production of testosterone (T) and 11-ketotestosterone (11-KT). Based on GSI, the male reproductive cycle was broken into three distinct phases. TUNEL positive staining was only observed in the Sertoli cells of mature spermatocysts during the degenerative testicular phase, suggesting that Sertoli cell death potentially plays a role in testicular degeneration and the regulation of sperm release. GSI, T, and 11-KT were all inversely correlated with daylength, while only T was inversely correlated with temperature. Captive male round stingrays subjected to water temperatures of 25 °C showed a significant decrease in plasma testosterone concentrations, but the same males exposed to ambient water temperatures (18 °–20 °C) exhibited T concentrations observed in wild male round stingrays during the recrudescent phase. Together, these findings suggest that temperature plays an important role in the regulation of testosterone, and may serve as an ultimate cue for reproduction in male round stingrays.

Effect of ‘PC Game Room’ use and polycyclic aromatic hydrocarbon exposure on plasma testosterone concentrations in young male Koreans

'PC Game Rooms' were first popularized in Korea, although the concept is now becoming popular worldwide. PC Game Rooms provide users with high-performance PC connected to the high-speed internet, and access to computer games. However, PC Game Room users are exposed to various hazardous agents such as cigarette smoke in a confined environment, and thus it is likely that excessive PC Game Room use involves abnormal exposure to polycyclic aromatic hydrocarbons (PAH) as well as being associated with disturbed sleep or circadian rhythm. In this cross-sectional study, the exposure to PAH was evaluated by measuring urinary 1-hydroxypyrene (1-OHP) and 2-naphthol. The correlations between PC Game Room use and PAH exposure and plasma testosterone and LH levels were analysed in 208 young male Koreans. Urinary 1-OHP concentrations increased (P = 0.0001) and plasma testosterone levels decreased (P = 0.0153) significantly with increased duration of PC Game Room use. Correlation analysis showed that plasma testosterone concentrations were significantly negatively correlated with urinary 1-OHP (r = -0.22, P = 0.0012) and 2-naphthol (r = -0.15, P = 0.0308) concentrations. Moreover, these associations persisted after adjusting for other independent variables. However, the duration of PC Game Room use itself was not found to be an independent significant determinant of plasma testosterone level. Rather, PC Game Room use increased PAH exposure, which decreased plasma testosterone level. The younger age group (15-19 years) showed a more prominent decrease in plasma testosterone concentrations with increasing duration of PC Game Room use than the older age group (20-24 years) (r2 = 0.355, P = 0.0301 versus r2 = 0.213, P = 0.0001). These results imply that the excessive use of PC Game Rooms is related to an adverse impact on sex hormonal status in young male Koreans via PAH exposure. This effect was more prominent in the younger age group.

Is there a role for PAPP-A in antenatal screening at mid-gestation?

The purpose of this study was to examine the effects of stress induced physiological changes in the gestating sow on postnatal sexual and endocrine development of male offspring. Ten boars, ranging from 160 to 185 days of age, were randomly chosen from sows which had been maintained under either stress or control conditions during mid-gestation. Blood samples were collected weekly from each boar (minimum of four weeks) at 30 min intervals over a common six-hour period via an indwelling anterior vena cava cannula. Plasma testosterone concentrations were determined by radioimmunoassay. In order to ascertain degree of sexual behavior, boars were exposed weekly to gilts in estrus and a subjective score assigned. No differences (P>.10) were found between prenatally stressed and control boars in overall mean testosterone concentration or libido score. A significant (P<.05) decrease in plasma testosterone concentration was detected in boars over age. Results suggest that mid-gestational stress of gestating sows does not affect the testosterone concentration or sexual behavior of boar off-spring.

Incomplete testicular feminization syndrome: studies of 17 beta-oestradiol-binding activity and aromatase activity in cultured genital fibroblasts showing impaired dihydrotestosterone-binding.

Dihydrotestosterone (DHT) and 17 beta-oestradiol binding, and aromatase activity were measured in cultured genital skin fibroblasts from two siblings with the incomplete testicular feminization syndrome. Whole-cell and nuclear DHT binding in the cells from both patients were reduced to 80% and 60%, respectively of those in a normal male subject. The nuclear oestradiol binding was not impaired in the fibroblasts from the patients whose plasma oestradiol was normal or a little elevated. Although gonadectomy led to a decrease in plasma testosterone concentration, the concentration of testosterone-binding globulin showed no change suggesting no apparent effect on testosterone-binding globulin synthesis by testicular steroids. There was no significant difference in aromatase activity of the fibroblasts between the patients and the normal male subjects. The relatively increased oestrogen concentration in the syndrome might result from oestrogen production in testes, but is unlikely to be from peripheral tissues such as fibroblasts. This is the first report to examine oestradiol binding and aromatase activity in the cells from the incomplete testicular feminization associated with impaired DHT binding. These findings may give new insight into the pathogenesis of abnormal male sexual differentiation in the patients with testicular feminization syndrome.

Androgens in the Aging Male

IN CONTRAST to the situation in women, where the menopause marks the end of the fertile period, in men fertility persists into old age. Nevertheless old age in men is accompanied by clinical signs, such as a decrease in muscle and bone mass, decrease in sexual hair growth, and decreased libido and sexual activity, suggesting decreased virility. These clinical signs are supported by histological evidence for a decreased Leydig mass and function. Evidence for decreased plasma testosterone in elderly men As to biochemical evidence for decreased androgenicity in elderly men, 25 yr ago the blood production rate of testosterone was reported to be decreased, which at least partially is caused by a decrease of the metabolic clearance. Whether or not aging is also associated with a decrease in plasma testosterone concentrations has long been highly controversial. Indeed, a large series of publications in the 1960s and early 1970s reporting decreased plasma testosterone concentrations in elderly

The effect of sodium monofluoroacetate on plasma testosterone concentration in Tiliqua rugosa (gray)

1. 1. Administration of multiple or single doses of sodium fluoroacetate (1080) to male Tiliqua rugosa caused a decrease in plasma testosterone concentration. 2. 2. A single dose of 100 or 250 mg 1080 kg −1 body weight decreased plasma testosterone by 52%. However, 25 mg kg −1 had little apparent effect on testosterone levels. When lizards were given the multiple dose equivalent of these doses over 12 days at 3 day intervals, the effect was much less dramatic with plasma testosterone concentration steadily declining over 15 days for the two higher doses. 3. 3. There was a suggestion of degeneration of seminiferous tubules in some individuals.

Seasonal variation of plasma testosterone in a wild population of male Eastern quoll, Dasyurus viverrinus (Marsupialia: Dasyuridae), from Tasmania

In the wild, male Eastern quoll, Dasyurus viverrinus, exhibit a synchronized sequence of increase and decrease in plasma testosterone concentration, body weight, and scrotal size in response to the breeding season. Basal concentrations of peripheral testosterone between 0.5 and 0.7 ng/ml circulate during the nonbreeding period. By April, 2 months prior to breeding, testosterone concentrations increased to around 1.6 ng/ml. This increase may reflect a resurgence in testicular activity, as scrotal size is maximal at this time. A synchronized testosterone peak of 5.0 ng/ml was observed during the mating period in early June. With the cessation of breeding, testosterone concentrations in resident males returned to basal levels by July; however, transient males maintained elevated levels for slightly longer. The timing of breeding and the short duration of the testosterone breeding peak enable the quoll to intensify its reproductive effort.

Sexual inhibition in a prosimian primate: a pheromone-like effect.

The effect of dominant urine odour on plasma levels of testosterone and cortisol was studied in the prosimian primate Microcebus murinus. This species shows a photoperiod-dependent cycle of sexual activity. In particular, mean testosterone levels vary from 15 nmol/l during the annual rest period to 245 nmol/l during the breeding season. When males of this solitary and territorial species are artificially grouped in captivity, they develop a social hierarchy which in turn results in physiological disorders, especially of reproductive function, in non-dominant individuals. Since olfactory behaviours appear to be important in the establishment and maintenance of the social structure, we have tested the effects of dominant odorant signals upon the sexual inhibition observed in male conspecifics. A preliminary experiment showed that a decrease in plasma testosterone concentrations could be induced by dominant scent marks. Furthermore, dominant urine odour alone was found to be sufficient to induce this modification. Plasma cortisol levels also increased in these animals. Conversely, when sexually inhibited males were olfactorily isolated from dominant urine odour, testosterone and cortisol concentrations returned to a normal seasonal level. These effects were observed even in males which had had no previous contact with the dominant urine donor. It is inferred from these results that a pheromone-like process could lead to sexual inhibition in male Microcebus murinus exposed to an odorant urinary signal produced by a dominant individual. Nevertheless, the endocrine response seems to vary according to the seasonal period of the sexual activity cycle which suggests that the social effect described is modulated by other external (e.g. photoperiodic) or internal (e.g. reproductive physiology) factors.

Rhythmical oscillations in rat testicular microcirculation as recorded by laser Doppler flowmetry.

We have earlier reported that local testicular blood flow, recorded by laser Doppler flowmetry, shows large oscillations with a frequency of 5-10 min-1. In the present study it is proposed that the recorded oscillations represent mainly local microvascular blood flow variations rather than variations in total testicular blood flow or tissue movements. The reasons for this are: (a) Blood flow simultaneously measured at two separate sites showed oscillations with different frequencies. (b) A local subcapsular injection of room-tempered saline under one probe site eradicated oscillations under that probe but not under another adjacent probe. (c) When the testicular capsule was split open, recordings of blood flow continued to show oscillations. (d) The amplitude of the oscillations was rather large (peak to peak value about 50% of mean flow value). No movements of the testicular surface were seen. A 20 min continuous infusion of 0.4 microgram/min noradrenaline did induce a decrease in plasma testosterone concentration, but did not change the mean blood flow. However, the oscillations nearly completely disappeared during the infusion period. The present study also shows that laser Doppler flowmetry is a versatile method and the rat testis provides a suitable organ in the study of the origin and functional importance of these oscillations.

Influence of exogenous melatonin on melatonin secretion and the neuroendocrine reproductive axis of intact male rats during sexual maturation.

The influence of daily sc administration of melatonin (5-100 micrograms/day) on sexual development of prepubertal and pubertal male rats was studied in vivo. Adult animals were also studied. When melatonin was injected daily into young animals starting at day 20 of age, dose-dependent reductions in plasma testosterone, testis and seminal vesicles weights, plasma FSH and LH levels, and pituitary GnRH receptor number were observed at day 40 or 45 of age when animals were killed. In contrast, prepubertal animals (5-20 days old) showed no significant responses to similar treatment with melatonin, whereas in adult animals (70-90 days old), melatonin elicited only a small decrease in plasma testosterone concentration. Melatonin analogs such as N-acetyl-serotonin and 5-hydroxytryptophol administered daily from 20-45 days of age did not produce any effect. Chronic melatonin administration from 20-50 days of life did not alter the occurrence of the nocturnal rise of circulating plasma melatonin, but did enhance its amplitude. Our results demonstrate that exogenous melatonin can inhibit or delay sexual maturation in the male rat if administered between 20 and 40 days of age and suggest that this inhibitory action is exerted at the hypothalamic and/or pituitary level.

Estrogen regulation of rat prostate androgen receptor

Injection of estrogens [estradiol (E 2), ethynyl estradiol (EE), RU 2858 (moxestrol), diethylstilbestrol (DES) or Zeranol] to adult male rats triggers an increase in the number of specific androgen binding sites measured by an exchange assay using [ 3H]-RU 1881 (methyltrienólone) in the presence of an excess of triamcinolone acetonide. These binding sites are androgen specific since only compounds with known androgenic properties (testosterone, dihydrotestosterone) are able to displace [ 3H]-RU 1881 specific binding. This increase does not seem to be mediated by the estrogen-induced decrease in plasma testosterone concentration, since the pattern of androgen receptor concentration obtained during 14 days of estrogen treatment is very different from that observed 14 days post-castration whereas the decrease in plasma testosterone concentration is similar in both cases. This increase is (1) related to the number of injections of the estrogen (the concentration of androgen binding sites doubles after 3 s.c. estradiol injections (25 μg/day) and is about 5 times higher after 14 injections), (2) dose-dependent, (3) related to the estrogen potency of the injected compound RU 2858 ⪢ EE ⪢ E 2 ⩾ DES ⪢ zeranol and (4) inhibited by the simultaneous administration of an anti-estrogen. Furthermore, whereas estrogen receptor was present in the prostate of intact male rats (1.3 pmol/g tissue) it was not detectable in 3 days-castrated rats. No increase in androgen receptor was observed after estrogen treatment in 3 dayscastrated rats. These results which suggest that the increase in androgen binding sites observed after estrogen treatment could be mediated by the estrogen receptor, are discussed in relation to the pharmacological and pathological effects of estrogens on the prostate.

LHRH and analogues as potential therapy for benign prostatic hyperplasia and hormone-dependent cancers.

In adult male rats, daily s.c. injections of 0.008-125 microgram luteinizing hormone releasing hormone (LHRH) or its analogue (D-Ala, des-Gly-NH2)LHRH ethylamide, led to significant differences in inhibitory effects on testicular function and accessory sex organ weights. The analogue was at least 35 times more potent than LHRH in reducing testicular LH/hCG receptors and 350 times more effective in decreasing plasma testosterone concentrations. In a second study, adult male rats treated with 25-2500 microgram LHRH daily for a 3-week period showed 85%-90% decrease in plasma testosterone concentrations. Treatment with 25 or 250 microgram LHRH effected a maximal 25% and 40% decrease of the ventral prostate and seminal vesicles, respectively, without affecting the testicular weight, the latter being reduced by 15% with the higher dose of 2500 microgram. The LHRH analogue is proposed for the treatment of prostatic and breast cancers while native LHRH could be an effective therapy for benign prostatic hyperplasia.

Peripheral plasma testosterone concentration and sexual behavior in young prenatally stressed boars

The purpose of this study was to examine the effects of stress induced physiological changes in the gestating sow on postnatal sexual and endocrine development of male offspring. Ten boars, ranging from 160 to 185 days of age, were randomly chosen from sows which had been maintained under either stress or control conditions during mid-gestation. Blood samples were collected weekly from each boar (minimum of four weeks) at 30 min intervals over a common six-hour period via an indwelling anterior vena cava cannula. Plasma testosterone concentrations were determined by radioimmunoassay. In order to ascertain degree of sexual behavior, boars were exposed weekly to gilts in estrus and a subjective score assigned. No differences (P>.10) were found between prenatally stressed and control boars in overall mean testosterone concentration or libido score. A significant (P<.05) decrease in plasma testosterone concentration was detected in boars over age. Results suggest that mid-gestational stress of gestating sows does not affect the testosterone concentration or sexual behavior of boar off-spring.

Decreased plasma testosterone concentrations in rams affected by ryegrass staggers

Feeding ryegrass, cut from pasture that had caused an outbreak of ryegrass staggers, to 10 mature rams caused a significant decrease in plasma testosterone concentrations in six animals. Six rams also developed staggers, but these did not all have decreased testosterone levels. This discrepancy suggests that toxic pasture could cause these two effects independently.

Circulating LH and FSH levels and testicular function in hamsters during light deprivation and subsequent photoperiodic stimulation.

The relationship between testicular function and peripheral gonadotropin levels was investigated in adult hamsters throughout a 60-day period of light deprivation and then again after a return to normal light cycles (L:D, 14:10). Hypophyseal LH and plasma LH and FSH concentrations declined slowly and progressively (at least 5-fold) during the 60-day period of constant darkness. Thedecline in gonadotropin release was associated with a 73% decrease in plasma testosterone concentrations and a 4-fold reduction in the capacity of testicular tissue to convert [7-3H]progesterone to [3H]testosterone in vitro (p < 0.05). Testis atrophy accompanied the collapse of the hypophysealgonadonal endocrine system as evidenced by a 98% reduction in the relative number of step 7 spermatids and the absence of step 17 spermatids from the seminiferous epithelium. Once previously light-deprived hamsters (i.e., 60 days) were exposed o L:D, 14:10 cycles, hypophyseal LH and plasma LH and FSH levels returned to near control levels w...

Suppression by the spironolactone metabolite canrenone of plasma testosterone in man.

Healthy male subjects were given orally a single dose of 5 mg canrenone per kg body weight. Canrenone caused a significant decrease in plasma testosterone concentration already 3 hrs after administration of the drug. Suppression of plasma testosterone concentration by 50 to 60 per cent persisted over 9 hrs. It is concluded that suppression of testosterone production is an important factor in the antiandrogenic activity of spirolactones in man.