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At least 289 records · Page 16Linked to original sources
PubMed1992

Basic fibroblast growth factor enhances testosterone secretion in cultured porcine Leydig cells: site(s) of action.

The effect and mechanism of action of basic fibroblast growth factor (bFGF) on testicular steroidogenesis were investigated using as a model primary cultures of purified porcine Leydig cells from immature intact animals. Basic FGF increased basal and human chorionic gonadotrophin (hCG)-induced testosterone accumulation (with an ED50 of 0.64 ng/ml bFGF, 35 pM) in the medium following a long-term treatment. The effects of bFGF (10 ng/ml, 72 h) were found at all hCG concentrations tested (0.001-1 ng/ml), the growth factor affecting the maximal steroidogenic capacity of the Leydig cells but not their sensitivity to the gonadotrophin. In this context, we have therefore investigated whether the stimulatory effect of bFGF on testosterone formation was related to an increase of the steroidogenic enzyme activities. The data obtained indicate that the growth factor did not affect the gonadotrophin action on the formation of delta 5-steroid hormone, namely dehydroepiandrosterone (DHEA) (evaluated in the presence of 10(-5) M WIN 24540, an inhibitor of 3 beta-hydroxysteroid dehydrogenase/isomerase). By contrast, bFGF (10 ng/ml, 72 h) was found to increase in a comparable manner the conversion of pregnenolone, DHEA and delta 4-androstenedione into testosterone, suggesting a stimulatory effect on 17 beta-hydroxysteroid dehydrogenase activity. Indeed, bFGF enhanced in a dose-dependent manner (ED50 = 39 pM) this enzyme activity evaluated through the conversion of delta 4-androstenedione to testosterone. These effects of bFGF on Leydig cell steroidogenic activity are probably exerted through specific membrane bFGF receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

17-Hydroxysteroid Dehydrogenases↗
PubMed2006

Horn growth related to testosterone secretion in two wild Mediterranean ruminant species: the Spanish ibex (Capra pyrenaica hispanica) and European mouflon (Ovis orientalis musimon).

Seasonal variations in the horn development and testicular activity of the Spanish ibex (Capra pyrenaica hispanica) (n=6) and European mouflon (Ovis orientalis musimon) (n=5) were monitored to determine the role of increasing testosterone concentration on the arrest of horn growth during the rutting season. Marked seasonal variations in the rate of horn growth (P<0.01) and testicular activity (P<0.001) were seen in both species, although the magnitude and timing of these changes were different (P<0.01). Horn growth rate was inversely correlated to seasonal levels in testosterone plasma concentration in both species (ibex: R=-0.45, P<0.01; mouflon R=-0.51, P<0.01). In the mouflon, the increase in plasma testosterone concentration recorded in September (P<0.05 compared with the lowest concentration) coincided with a significant reduction in horn growth (P<0.05). In the ibex, the increase in plasma testosterone concentration in October (P<0.05 compared with the lowest concentration) was associated with a significant arrest of horn growth in November (P<0.05). These results appear to support the hypothesis that high peripheral plasma levels of testosterone are linked with the seasonal arrest of horn growth during the rutting period.

Animals↗
PubMed1985

Effect of a gonadotropin-releasing hormone agonist on luteinizing hormone and testosterone secretion and testicular histology in male rhesus monkeys.

Three adult male rhesus monkeys were treated for 20 weeks with a gonadotropin-releasing hormone (GnRH) agonist (Ag; Wy-40972; Wyeth Laboratories, Philadelphia, PA) using osmotic minipumps. Ag administration resulted in a transient increase and then a precipitous decrease in the concentration of luteinizing hormone (LH) and testosterone (T). After 5 weeks, serum levels of LH were undetectable (less than 0.2 microgram/ml), while serum T was always detectable, but continued to fall throughout the period of Ag administration. The serum LH and T response to 50 micrograms of GnRH was abolished by 4 weeks of Ag treatment, and this effect persisted through the treatment period. Testicular histology at 20 weeks of Ag treatment exhibited diffuse atrophy of seminiferous tubules, suppressed germinal cell division, and the absence of spermatids or spermatozoa. There was no evidence of testicular necrosis or calcification of the seminiferous tubules. Following the termination of Ag infusion, serum LH and T concentrations rebounded to levels that exceeded pretreatment values for a 5-week period before falling back to baseline levels. A complete restoration of spermatogenesis and testicular volume occurred by 12 weeks after treatment. These data suggest that continuous Ag administration is an effective method of reversibly disrupting spermatogenesis in the male rhesus monkey.

Animals↗
PubMed1988

Testosterone-secreting adrenocortical tumor in a pubertal girl. Case report and review of the literature.

A girl aged 12 years and 10 months presented with deepening of the voice first noted 7 months earlier. Pubertal development was almost completed. The girl had regular monthly menses and no signs of hirsutism, clitoris enlargement or Cushing's disease. Serum testosterone was about threefold above normal, whereas dehydroepiandrosterone was in the upper normal range. The 17-ketosteroids as well as the gas-chromatographically analyzed 5 alpha and 5 beta derivatives of testosterone from urine were slightly increased. Other serum and urinary steroids were normal. Dynamic tests of the endocrine function exhibited inconclusive results. Ultrasonography revealed no ovarian cysts. A small, left-sided adrenal mass was identified by computed axial tomographic scan and removed by surgery. There were no signs of local metastasis nor of vascular extension. The histopathological diagnosis was adrenocortical carcinoma. 5 months after surgery, the preoperatively elevated steroid levels had returned to normal.

Adolescent↗
PubMed1983

Effect of experimental microvascular orchidopexy on testosterone secretion in the dog.

This study was undertaken to investigate the endocrine function of the testis that was autotransplanted by microvascular techniques in 10 healthy dogs. After a control period of 4 weeks, hemicastration was carried out, and 4 weeks later the experimental orchidopexy was done. Finally, the transplanted testis was removed after another 4 weeks. Peripheral blood testosterone levels were measured at weekly intervals during the control period, after hemicastration, after autotransplantation and after removal of the transplanted testis. 1 week before each operation, 500 IU human chorionic gonadotrophin (HCG) was given intravenously and the peripheral testosterone levels were determined after 2 and 24 h. During each operation a testicular venous blood sample was taken for testosterone measurements. No differences were found between the basal and HCG-stimulated peripheral plasma levels of testosterone after the hemicastration and the orchidopexy in comparison with the values during the control period. There was a statistically significant positive correlation between the testosterone levels in the testicular venous and peripheral plasma samples. It was concluded that microvascular anastomosis was successful in every case.

Animals↗
PubMed1994

[Influence of intratesticular injections of tamoxifen on spermatogenesis and testosterone secretion in the rat].

Three groups of adult Wistar rats were injected every second day with: 5 or 10 or 20 micrograms of tamoxifen (Tx) to the right testis. Left testis was injected with the same volume of solvent. Control group received the solvent for Tx. Animals were killed after 15 days. Blood samples were taken from heart for testosterone determinations. Both testes were taken for histological examination and quantitative analysis of seminiferous epithelium was performed. Testosterone was analysed with radioimmunoassay method. It was demonstrated that intratesticular supply of Tx caused significant rise in the number of type A spermatogonia and significant increase of testosterone concentration in the blood. It is concluded that Tx influences spermatogenesis in adult rats through stimulation of the earliest steps of gamete formation. Testosterone may or may not mediate this effect.

Animals↗