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PubMed1984

Profiles of luteinizing hormone, follicle-stimulating hormone, testosterone and prolactin in rams of diverse breeds: effects of contrasting short (8L:16D) and long (16L:8D) photoperiods.

Mature rams of Polled Dorset, Finnish Landrace, Rambouillet and Suffolk breeding were maintained in a temperature-controlled environment and exposed to two consecutive cycles of short (8L:16D) followed by long (16L:8D) days. Serum hormone concentrations were determined in weekly samples and in 24-h profiles characterized at the end of each lighting schedule (i.e., 12, 24, 36 and 48 weeks). In all four breeds, the pituitary-testicular axis was more active during short days as compared with long days and the magnitudes of changes in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone concentrations were greater for the two most seasonal breeds, Finnish Landrace and Suffolks. In comparison to other breeds, Finnish Landrace rams had significantly (P less than 0.05) higher mean LH levels, showed the greatest number of LH peaks/24 h, and had the highest mean testosterone levels at the end of both periods of short days, while Rambouillet rams had significantly (P less than 0.05) lower testosterone. Rambouillets also showed the smallest changes in pulsatile LH and testosterone secretion and displayed the least number of LH peaks/24 h following short days. Serum FSH levels were significantly (P less than 0.05) higher in Finnish Landrace and Suffolk rams than in Polled Dorsets and Rambouillets after 12 weeks of short days. Breed differences in serum LH, FSH and testosterone were not apparent following long days. Prolactin levels in Rambouillet rams were significantly (P less than 0.05) lower than in the other breeds following both periods of long days. These results indicate that breed differences exist in mature rams with regard to hormone secretory profiles. Breed differences in serum gonadotropin and testosterone are only apparent during short days when the hypothalamo-pituitary-testicular axis in rams is considered most active. Likewise, breed differences in prolactin are noticeable only during long days when secretion of this hormone is enhanced. Breed differences in LH, FSH and testosterone secretion in rams during short days might be related to seasonality of mating and/or fecundity of breed types.

Animals↗
PubMed1981

The androgen status of aging male rats.

In male Sprague-Dawley rats between 3-24 months of age, plasma concentrations of testosterone declined by more than 50% while concentrations of LH in plasma remained relatively constant. During the same interval, body weight rose almost 50%, suggesting that total circulating amounts of testosterone, assuming a proportional expansion of plasma volume, remained relatively constant with increasing age and that total LH in the circulation actually increased in older rats. This assumption was justified by demonstrating that blood plasma volume increased in proportion to body weight over the range of ages and weights represented by rats in this study. Plasma testosterone levels achieved after the injection of gonadotropin were significantly lower in the oldest rats, but when adjusted for increased plasma volume, total testosterone added to the circulation in response to injected gonadotropin did not diminish with age. Age-related change was not detected in testosterone secretion by decapsulated rat testes, either under control conditions or after the addition of gonadotropin to the incubation medium. The average volume of individual Leydig cells remained near young adult values with advancing age, while the total number of Leydig cells per testis rose slightly in the oldest rats. Hence, diminished androgen status in old rats could not be attributed to functional or numerical deficits in the Leydig cell population. Instead, low plasma testosterone levels may have resulted from two interrelated extratesticular phenomena, dilution of secreted hormone with the expanded volume of plasma in a significantly larger body mass, and failure of LH levels to rise sufficiently to stimulate additional testosterone secretion. (Endocrinology 108: 712, 1981)

Aging↗
PubMed1978

Age-related changes in responsiveness of rat Leydig cells to hCG.

The responsiveness of decapsulated testes and isolated Leydig cell preparations from rats (30-80 days of age) to a constant dose of 3 ng hCG/2 ml was assessed by comparison of the production of testosterone and "total 17beta-hydroxy androgen" (17beta-HA). When testosterone secretion was used as the index of response, there was a marked increase in the production with age by decapsulated testes and also by equal numbers of Leydig cells. When 17beta-HA was taken as the response parameter this increase was only marginal for the decapsulated testes and there was an age-dependent decrease when expressed per 10(6) cells. These differences probably reflect changes in the metabolism of testosterone to 5alpha-reduced products with increasing age because 80% of androgen secreted at 30 days is 3alpha-androstanediol and 86% is secreted as testosterone at 80 days. We conclude that for studies on hCG responsiveness and the steroidogenic capacity of immature rat Leydig cells (a) testosterone is an inappropriate response parameter and (b) this response undergoes a decrease rather than an increase during prepubertal development.

Aging↗
PubMed2003

Androgens and male fertility.

Androgens play a crucial role in the development of male reproductive organs such as the epididymis, vas deferens, seminal vesicle, prostate and the penis. Furthermore, androgens are needed for puberty, male fertility and male sexual function. High levels of intratesticular testosterone, secreted by the leydig cells, are necessary for spermatogenesis. Intratesticular testosterone is mainly bound to androgen binding protein and secreted into the seminiferous tubules. Inside the sertoli cells, testosterone is selectively bound to the androgen receptor and activation of the receptor will result in initiation and maintenance of the spermatogenic process and inhibition of germ cell apoptosis. The androgen receptor is found in all male reproductive organs and can be stimulated by either testosterone or its more potential metabolite dihydrotestosterone. Severe defects of the androgen receptor may result in abnormal male sexual development. More subtle modulations can be a potential cause of male infertility. Treatment of an infertile man with testosterone does improve spermatogenesis, since exogenous administrated testosterone and its metabolite estrogen will suppress both GnRH production by the hypothalamus and Luteinising hormone production by the pituitary gland and subsequently suppress testicular testosterone production. Also, high levels of testosterone are needed inside the testis and this can never be accomplished by oral or parenteral administration of androgens. Suppression of testosterone production by the leydig cells will result in a deficient spermatogenesis, as can be seen in men taking anabolic-androgenic steroids. Suppression of spermatogenesis by testosterone administration is also the basis for the development of a male contraceptive. During cytotoxic treatment or irradiation suppression of intratesticular testosterone production cells may prevent irreversible damage to the spermotogonial stem cells.

Androgens↗
PubMedDate not supplied

Negative feedback regulation of pulsatile LH secretion during treatment with an LHRH antagonist in rams.

Suppression of LH and testosterone secretion in sexually active rams by the short-term administration of an LHRH antagonist results in a compensatory increase in the release of LHRH from the hypothalamus. This is inferred from the observed increase in the frequency of LH pulses in peripheral blood during the period of recovery when the pituitary regains its responsiveness to LHRH. To investigate the nature of the inhibitory feedback signal which triggers this compensatory response, a single intravenous injection of 1 mg of an LHRH antagonist (28 micrograms/kg; N-Ac-D-pCl-Phe 1, D-pCl-Phe 2, D-Trp 3, D-hArg (Et 2) 6, D-Ala 10, LHRH) was given to groups of intact, testosterone-implanted castrated and castrated rams housed under stimulatory short days. Pulsatile LH secretion was monitored in blood samples collected every 10 min for 34 h. The treatment caused an immediate blockade of LH pulses in all three groups of rams followed by a progressive recovery of LH secretion from 12-30 h. Compared to the pretreatment period, intact rams showed a significant increase in frequency of LH pulses during the recovery period. Castrated rams did not show this increase, with or without supplementary testosterone. Since the circulating testosterone concentration decreased after the blockage of LH secretion in the intact rams, but not in the castrated or testosterone-implanted castrated rams, we conclude that it is the reduction in the steroid negative feedback signal which leads to a compensatory increase in the activity of the LH pulse generator.

Amino Acid Sequence↗
PubMed2006

A stochastic model of oscillatory blood testosterone levels.

A continuous-time, discrete-state stochastic model of testosterone secretion in men is considered. Blood levels of testosterone in men fluctuate periodically with a period of 2-3 h. The deterministic model, on which the stochastic model considered here is based, is well studied and has been shown to have a globally stable fixed point. Thus, no sustained oscillations are possible in the deterministic case. However, the stochastic model does observe periodic, pulsatile behavior. This demonstrates how oscillations can occur due to a switching behavior dependent on the random degradation of testosterone molecules in the system. The Gillespie algorithm is used to simulate the hormone secretion model. Important parameters of the model are discussed and results from the model are compared to experimental observations.

Biological Clocks↗
PubMedDate not supplied

Effects of age on hormone levels and in vitro steroidogenesis by rat ovary and adrenal.

In order to evaluate age-related changes in ovarian and adrenal steroid production, in vitro steroid production by adrenal glands and ovaries from young (3-4 mo) and middle-aged (10-11 mo) cycling rats was compared to serum steroid and gonadotropin levels on each morning of the estrous cycle. Basal LH levels were not different between young and mid-aged cycling rats except on estrus, when elevated estrogen (E) levels were correlated with depressed LH in the mid-aged rats. Basal FSH levels were generally elevated in mid-aged cycling and mid-aged constant estrus (CE) rats, but the FSH rise on estrus morning was not seen in the mid-aged rats. Serum progesterone levels were not changed with age or reproductive state, although in vitro ovarian progesterone secretion was decreased in mid-aged CE rats. Adrenal progesterone secretion increased significantly with age. Serum total testosterone was similar in young and mid-aged cycling and mid-aged CE rats, despite a highly significant increase in in vitro testosterone secretion by the CE ovary. Serum estradiol (E2) levels were significantly elevated on proestrus and estrus in the mid-aged rats. Although estrone (E1) levels appeared higher in the mid-aged than in the young cycling rats, the differences were not significant. Mid-aged CE rats had significantly elevated serum levels of both E1 and E2. In vitro ovarian estrone production was depressed in mid-aged cycling rats. Adrenal total estrogen production was similar in young and mid-aged animals. These results demonstrate that serum gonadotropin and steroid levels are altered in aging female rats prior to the loss of reproductive cycles. Changes in serum steroid levels are probably due to changes in circulating LH and FSH levels or the ovarian response to these gonadotropins, but changes in vitro basal steroid production suggest that intrinsic ovarian function may also change with advancing age. As rats enter a CE state, alterations in basal ovarian and adrenal steroid production are seen and may be partially responsible for maintenance of the acyclic state.

Adrenal Glands↗
PubMed2005

Changes in ovarian steroidogenesis in insulin-resistant, type 2 diabetic Goto-Kakizaki rats after thyroidectomy and gonadotropin treatment.

The present study used thyroidectomized insulin-resistant, type 2 diabetic Goto-Kakizaki (GK) rats to assess whether insulin resistance and hypothyroidism modulate ovarian physiology. Animals were treated with daily injections of 5 IU equine chorionic gonadotropin for 5 days starting 1 week after thyroidectomy. Control groups included rats of GK and control (Wistar) strains treated only with equine chorionic gonadotropin or thyroidectomy, or with no treatment (intact). In Wistar rats, equine chorionic gonadotropin injections tended to increase the serum concentrations of luteinizing hormone (LH) and testosterone more in the thyroidectomy group than in intact rats. Similar changes in LH and testosterone were observed in the thyroidectomy + equine chorionic gonadotropin and equine chorionic gonadotropin groups of GK rats, but the LH and testosterone levels in the thyroidectomy + equine chorionic gonadotropin group were significantly higher in GK rats. Expression of ovarian LH receptor messenger RNA (mRNA) was enhanced by thyroidectomy. The LH receptor mRNA levels were significantly higher in the thyroidectomy+equine chorionic gonadotropin group of GK rats than in the corresponding group of control rats. These results indicate that hypothyroidism in animals with insulin resistance and type 2 diabetes promotes LH and testosterone secretions, and suggests that the enhanced-testosterone levels is partially mediated by the enhancement of LH receptor expression and an increase in the serum level of LH.

Animals↗
PubMed2004

The effects of intracerebroventricular infusion of prolactin in luteinizing hormone, testosterone and growth hormone secretion in male sheep.

This study tested a hypothesis that the enhancement of the prolactin (PRL) concentration within the central nervous system (CNS) disturbs pulsatile luteinizing hormone (LH) and growth hormone (GH) secretion in rams that are in the natural breeding season. A 3h long intracerebroventricular (icv.) infusion of ovine PRL (50 microg/100 microl/h) was made in six rams during the daily period characterized by low PRL secretion in this species (from 12:00 to 15:00 h); the other six animals received control infusions during the same time. Blood samples were collected from 9:00 to 18:00 h at 10 min intervals. A clear daily pattern of LH secretion was shown in control animals, with the lowest concentration at noon and an increasing basal level around the time of sunset (P < 0.001). No significant changes in LH concentration occurred in PRL-infused animals and the concentration noted after infusion of PRL was significantly (P < 0.05) lower than after the control infusion. The frequency of LH pulses tended to decrease in rams after PRL treatment. The changes in LH secretion clearly carried over to the secretion of testosterone in the rams of both groups. The GH concentrations changed throughout the experiment in both groups of rams, being higher after the infusions (P < 0.001). However, the mean GH concentration and GH pulse amplitude noted after PRL infusion were significantly lower (P < 0.001 and P < 0.05, respectively) from those recorded in the control. The continued fall in PRL secretion observed in rams following PRL infusion (P < 0.05 to P < 0.001) indicates a high degree of effectiveness of exogenous PRL at the level of the CNS. In conclusion, maintenance of an elevated PRL concentration within the CNS leads to disturbances in the neuroendocrine mechanisms responsible for pulsatile LH and GH secretion in sexually active rams.

Animals↗
PubMed1993

Effects of corticotropin-releasing hormone on luteinizing hormone, testosterone, and cortisol secretion in intact male rhesus macaques.

We previously have shown that 6 h of restraint stress in intact male rhesus macaques (Macaca mulatta) suppresses plasma levels of both LH and testosterone and that this effect lasts beyond the period of restraint. Since corticotropin-releasing hormone (CRH) inhibits both the GnRH pulse generator and LH release in ovariectomized macaques and is generally thought to be the central mediator of stress-induced inhibition of gonadotropin release, we investigated the influence of CRH administration on LH and testosterone in unrestrained intact male rhesus macaques. Blood samples were collected from 5 intact male macaques at 15-min intervals for 15 h from a remote site. During this time, each animal received a 4-h infusion of CRH (100-micrograms bolus followed by 100 micrograms/h for 4 h) through an indwelling jugular catheter. Blood samples were collected for an additional 8 h after cessation of the CRH infusion. ACTH and cortisol levels were significantly elevated during and after the CRH infusion and were comparable to levels observed during restraint. Although LH levels appeared lower in animals given CRH, they were not different from those in untreated control males. In some animals, CRH appeared to stimulate or prolong LH release. Testosterone levels in CRH-treated animals were significantly lower than in controls both during and after CRH administration. In some instances, increases in plasma LH were not accompanied by a rise in testosterone. This would suggest that as was observed in restrained animals, stress exerts either a direct or an indirect inhibition of testicular testosterone secretion. The present data indicate that this effect may be mediated by CRH.

Animals↗
PubMed2005

Effect of troglitazone on the excess testosterone and LH secretion in thyroidectomized, insulin-resistant, type 2 diabetic Goto-Kakizaki rats.

Our previous study suggested that hypothyroidism in Goto-Kakizaki (GK) rats with insulin resistance and type 2 diabetes elevates their serum testosterone and luteinizing hormone (LH) levels and ovarian LH receptor messenger RNA (mRNA) expression. The present study assessed the effects of troglitazone (Tro), an insulin-sensitizing agent, on these hypothyroidism-induced hormonal changes in GK rats. GK and normal (Wistar strain) female rats were thyroidectomized (Tx) and then injected with 5 IU of equine chorionic gonadotropin (eCG) for 5 d starting 1 wk after thyroidectomy (the control groups). In the test groups, Tx GK and Wistar rats were injected with both eCG and Tro (100 mg kg-1) po for 5 d. Tro treatment had no effect on the elevated LH serum levels in eCG-treated Tx GK rats but suppressed their enhanced serum testosterone levels as well as significantly decreasing their LH receptor mRNA expression. Tro lowered testosterone and LH receptor mRNA levels in cultured theca cells. These results indicate that Tro lowers the elevated testosterone secretion and ovarian LH receptor mRNA expression that is induced in GK rats by Tx and gonadotropin treatment, which suggests that insulin resistance may be involved in enhancing testosterone production and LH receptor expression in the ovary.

Animals↗
PubMed1981

Recovery of testicular functions after surgical treatment of experimental cryptorchidism in the rat.

When rats were made unilaterally cryptorchid at 17 days of age (before spontaneous descensus), the further maturation of the testis was prevented. At 34 days of age, the abdominal testis was smaller than the scrotal testis and showed less secretion of the Sertoli cell specific androgen binding protein (ABP). In 120-130 days old rats that were made bilaterally cryptorchid at 17 days of age, testicular weight, histology, secretion of fluid and ABP were restored and testosterone secretion and fertility were normal if orchidopexy was performed at 33 days of age. If the orchidopexy was delayed until 59 days of age, the recovery of testicular function and morphology was only partial. The results show that in the rat, the testicular damage caused by cryptorchidism is reversible, if the abdominal testis is surgically descended during early sexual maturation.

Androgen-Binding Protein↗
PubMed1994

Calcitonin inhibits testosterone and luteinizing hormone secretion through a mechanism involving an increase in cAMP production in rats.

Effects of calcitonin peptides, including human calcitonin (hCT), salmon calcitonin (sCT), and calcitonin gene-related peptide (CGRP), on the secretion of testosterone and luteinizing hormone (LH) in male rats were studied. Male rats were injected intravenously with human chorionic gonadotropin (hCG), calcitonin peptides, or hCG plus calcitonin peptides. Blood samples were collected at several intervals following hormone challenge. In an in vitro experiment, testis blocks were incubated with hCG (0, 0.05, 0.5, or 5 IU/ml) or hCG (0.5 IU/ml) plus calcitonin peptides (0-10(-9) or 10(-6) M) at 34 degrees C for 30 minutes. Both medium and plasma samples were extracted by ether and analyzed for testosterone by radioimmunoassay (RIA). The concentration of calcium in each plasma sample was measured by an automatic calcium analyzer. The anterior pituitary gland (AP) was incubated with or without calcitonin peptides (0-10 nM) at 37 degrees C for 30 minutes. They were then incubated with gonadotropin releasing hormone (GnRH, 10 nM) for a further 30 minutes. The concentration of LH in AP medium was measured by RIA. The accumulation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in both testicular tissues and APs were measured by RIA. A single intravenous injection of calcitonin peptides decreased the basal and hCG-stimulated levels of plasma testosterone gradually from 60 to 180 or 360 minutes after challenge. The plasma calcium was not altered by the injection of calcitonin peptides and/or hCG. Administration of calcitonin peptides in vitro resulted in a dose-dependent inhibition of both basal and hCG-stimulated release of testosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed2000

Gonadal source of testosterone metabolites in urine of male cotton-top tamarin monkeys (Saguinus oedipus).

Examining gonadal function in the small excitable cotton-top tamarin monkey (Saguinus oedipus) requires noninvasive sampling techniques. Two studies were performed to identify the quantifiable urinary metabolites of testosterone in cotton-top tamarins and which of the measurable metabolites would best reflect a gonadal source of testosterone secretion. In the first study, we injected unlabeled testosterone i.m. in males at either 500-ng or 1-microg levels. Urine samples were analyzed for androgens and estrogens. Testosterone and dihydrotestosterone (DHT) increased significantly following the injections in test males but not in control males. No significant increases in androstenedione occurred. Mean levels of estradiol and estrone did not consistently increase during the 5 days following injection. In the second study, a gonadotropin-releasing hormone antagonist, Antide, was used to block LH stimulation of gonadal steroidogenesis. Males given Antide at either a 6 mg/kg dose or an 18 mg/kg dose showed significantly lower levels of urinary LH than controls. At the higher Antide dose, testosterone levels were significantly reduced during weeks 1 and 2 posttreatment, whereas DHT levels significantly declined during the 2nd week posttreatment. Estradiol levels were highly variable prior to treatment but decreased significantly following treatment, whereas estrone levels remained variable throughout. These results indicate that measurement of urinary testosterone and possibly DHT reflect gonadal function in male cotton-top tamarins. Other sources of urinary estrogens may occur for the male cotton-top tamarin, but these data suggest that a substantial part of urinary estradiol is from gonadal sources, whereas urinary estrone appears to be mainly from extragonadal sources.

Androstenedione↗
PubMed1980

Androgen receptors in the diabetic rat.

Male rats rendered diabetic by IV streptozotocin (65 mg/kg body weight) were treated with exogenous insulin or testosterone. Charcoal-coated dextran and polyacrylemide gel electrophoresis techniques were employed in studying the characteristics of androgen (R1881) binding to prostate cytosol protein. In comparison with normal (N) rats, the replacement therapy of diabetic (D) animals with insulin (D + I) or testosterone (D + T) was able to restore epididymal weight (N = 0.40 +/- 0.04 g; D = 0.18 +/0 0.02 g; D + I = 0.42 +/- 0.05 g; D + T = 0.40 +/0 0.06 g) and total prostate weight (N = 0.24 +/- 0.02 g; D = 0.15 +/- 0.02 g; D + I = 0.24 +/- 0.05 g; D + T = 0.35 +/- 0.06 h). Testicular endogenous content of testosterone was restored after insulin treatment (N = 154 +/- 13 ng/testis; D = 41 +/- 5 ng/testis; D + I = 142 +/- 9 ng/testis), and significant improvements of serum testosterone levels were also achieved (N = 540 +/- 64 ng/100 ml; D = 238 +/- 37 ng/100 ml; D + I = 358 +/- 18 ng/100 ml). Prostate cytosol of streptozotocin-diabetic rats had strongly lowered capacity for 3H-R1881 binding compared with controls (94 and 12 fmol/mg protein, respectively). Testosterone treatment produced a 3.3-fold improvement of this lowered value, whereas the increment seen with insulin was less (1.5-fold). It is emphasized that some of the improvements caused by insulin replacement therapy in diabetic animals are due to the partial restoration of testosterone secretion. Thus, the combined actions of insulin and testosterone (instead of insulin alone) seem to be of major importance in the maintenance and regulation of accessory sex glands function.

Animals↗
PubMed1992

Effect of Thymomodulin on luteinizing hormone, prolactin and testosterone in male rats.

The effect of Thymomodulin (TMD), a calf thymus derivative, on luteinizing hormone, prolactin and testosterone was studied in male rats after acute and chronic treatment. The results showed that the stimulatory action on prolactin and testosterone secretion after acute (prolactin) or one month chronic (testosterone) treatments completely vanished during six month chronic administration. No effect was observed on luteinizing hormone after acute or chronic treatment.

Animals↗
PubMed1989

Evaluation of the human testis and its age-related dysfunction.

The human testis has been evaluated by its endocrine function, daily sperm output in ejaculates, general appearance of seminiferous tubules, differential cell counts in the testis, and daily sperm production. Within-subject variation for total sperm count in ejaculates is extremely high at 42% to 75% coefficient variation. This variation can be reduced to 12% by averaging the counts obtained for the last three of five daily ejaculates. Plasma FSH concentrations are particularly useful in assessing the status of seminiferous epithelium and/or its Sertoli cell function in infertile men. In aged men, plasma LH, FSH, and estradiol concentrations are higher while plasma testosterone, free testosterone, and the ability of the testis to secrete testosterone following stimulation are reduced. Other age-related changes in human testes include a high incidence of azoospermia, reduced sexual activity, reduced testicular size, impaired spermatogenesis, reduced tubular length, increased thickness of tubular boundary tissue, sclerosis, focal mononuclear orchitis, and dilation of the rete testis. Due to the long duration of the spermatogenic cycle and low numbers of germ cells in human testis, daily sperm production per g parenchyma (efficiency of spermatogenesis) is much lower in humans than in other species. Testicular parenchymal weight, proportion of testis occupied by seminiferous epithelium, volume of seminiferous epithelium, and daily sperm production are significantly reduced in aged men. In various species, including man, germ cell degeneration occurs during spermatocytogenesis, meiosis, and/or spermiogenesis. Germ cell degeneration plays a pivotal role in spermatogenesis, but the mechanisms of degeneration, its etiology, and approaches for its prevention remain unclear.

Adult↗
PubMed1985

The effect of testicular irradiation on established BPH in the dog: evidence of a non-steroidal testicular factor for BPH maintenance.

Irradiation of the testes of four to 13-year-old male beagles with benign prostatic hyperplasia (BPH) was undertaken to attempt to evaluate the possibility that the testes secrete a non-androgenic accessory sex gland-stimulating substance that may have a critical role in the development of BPH. Available evidence indicates that development of prostatic hyperplasia in dog and man is dependent on testicular secretions and that testes irradiation is unlikely to alter testosterone secretion appreciably but does produce profound effects on the seminiferous tubules. Thirteen non-irradiated and shoulder irradiated control and 16 beagles subjected to 1500 to 2200 rads single dose testis irradiation had pre-irradiation, interval post-irradiation and terminal caliper measurements of prostatic length, width and depth, prostatic and testicular biopsies, and determination of serum testosterone and estradiol levels. Four beagles survived in a group observed for 109 weeks post testis irradiation, 12 in a group observed for 51 and 10 in a group observed for 59 weeks. The wet weight of the prostate was determined at sacrifice. Ratios of the final/initial length and width and final actual/initial calculated weight of the prostate were significantly decreased in testis-irradiated as compared to control beagles. Histologic evaluation also demonstrated a significant difference in degree of prostatic stimulation in control and testis-irradiated groups. The serum testosterone and estradiol levels were not significantly different in the testis-irradiated and control beagles. These observations indicate that irradiation of the testes of beagles with BPH alters the size, weight and histology to suggest decreased stimulation of the prostate without producing an identifiable change in the serum levels of the steroid hormones studied. The data support the hypothesis that the testis of the aging beagle secretes a non-androgenic and probably non-steroidal prostatic stimulating substance which is affected by irradiation of the testis.

Animals↗