Intratesticular Control Of Steroidogenesis

Sharpe, Richard M.

doi:10.1111/j.1365-2265.1990.tb03916.x

Cited by 84 publications

(40 citation statements)

References 106 publications

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“…Details of both intratesticular and plasma concentrations of testosterone are necessary before the relationship between testosterone and testicular apoptosis during seasonal regression can be clarified. In addition, other variables, such as expression of 3β-hydroxysteroid dehydrogenase (3β-HSD), aromatase activity, oestradiol production, and cofactor regulation, can affect testis concentrations of testosterone (Sharpe, 1990), as well as pathways regulated by testosterone. Aromatase protein expression differs seasonally in bank vole (Clethrionomys glareolus) testes (Bilinska et al, 2000), as do testicular 3β-hydroxysteroid dehydrogenase concentrations , 2001b.…”

Section: Role Of Testosteronementioning

confidence: 99%

Mediation of seasonal testicular regression by apoptosis

Young¹

2001

Reproduction

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Seasonal rhythms in physiology and behaviour are characteristic of most temperate and boreal species (Bronson, 1989). Synchronizing energetically demanding biological functions to the most favourable time of the year enables individuals to cope with recurring stressors such as seasonal declines in food or water availability, or annual fluctuations in ambient temperature. Environmental factors such as food availability, social cues, ambient temperature and the initial predictive cue of daylength (photoperiod) can facilitate or inhibit reproductive function seasonally. These factors maintain testicular function during favourable times of the year in some species (for example, birds), and induce testicular regression or atrophy when environmental conditions are less favourable in others (for example, small mammals). Environmental factors regulate testicular function through the hypothalamic-pituitary-gonadal (HPG) axis. Photoperiod serves as the primary predictive factor in the regulation of reproductive timing in long-and short-day breeding mammals and in most bird species (Wingfield and Kenagy, 1991;Bronson and Heideman, 1994). The general long-day breeding rodent response to seasonal changes in daylength is shown (Fig. 1); however, the actual HPG response to photoperiod is distinct among different species of birds, reptiles and mammals. Supplementary cues such as food and water availability also affect reproductive function directly, serving to fine-tune the initial, general reproductive response to photoperiod (Wingfield and Kenagy, 1991). Environmental factors that stimulate or maintain reproduction promote synthesis and secretion of GnRH from the hypothalamic median eminence, and positively regulate secretion of the gonadotrophins (LH and FSH) from the anterior pituitary (Bronson and Heideman, 1994). In contrast, non-stimulatory environmental factors decrease GnRH (pulse amplitude and frequency) release, resulting in testicular atrophy, reduced spermatogenesis and diminished testosterone production from Leydig cells, the steroidogenic somatic cells in the testicular interstitium (Sinha Hikim and Swerdloff, 1999).During the transition from the breeding to the nonbreeding state, males in most seasonally breeding species undergo 40-90% atrophy in testis mass. Cells must either undergo marked reduction in size, increases in the rate of cell death, or both, to achieve the reduction in volume observed during regression. The rate of cell division may decrease in the testis during regression, indirectly contributing to seasonal atrophy; however, total testicular DNA content in rodents is reduced with non-stimulatory photoperiod exposure, indicating an increase in cell death during regression (Desjardins and Lopez, 1983). Recent studies have examined complex changes that occur in testicular cells during seasonal reproductive regression. In this review, the contribution of apoptosis, or programmed cell death, in the mediation of seasonal atrophy is discussed. Specifically, the review focuses on the interactions of gona...

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Section: Role Of Testosteronementioning

confidence: 99%

Mediation of seasonal testicular regression by apoptosis

Young¹

2001

Reproduction

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“…Hormonal response is accomplished via specific membrane receptors on granulosa cells and Sertoli cells, causing adenylate cyclase activation and thereby secretion and/or synthesis of various factors essential for target cell differentiation and gamete maturation (1,2).…”

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confidence: 99%

Single-Dose Pharmacokinetics and Pharmacodynamics of Recombinant Human Follicle-Stimulating Hormone (Org 32489) in Gonadotropin-Deficient Volunteers

Mannaerts

Shoham

Schoot

et al. 1998

Fertility and Sterility

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Objective: To assess safety, pharmacokinetic, and pharmacodynamic properties of recombinant human follicle-stimulating hormone (FSH; Org 32489, Organon International, Oss, the Netherlands) after a single intramuscular injection in the buttock. Design:In a prospective study, safety variables, serum FSH, luteinizing hormone, inhibin, estradiol (females only), and testosterone (males only) were evaluated up to a maximum of 11 days after injection of 300 IU recombinant FSH. Setting: Four specialist Reproductive Endocrinology and Infertility units.Volunteers: Fifteen men and women exhibiting all pituitary gonadotropin deficiency. Result(s):A single bolus of 300 IU recombinant FSH was well tolerated, and no drug-related adverse effects were noted. Comparison of before and after treatment safety variables, including serum antirecombinant FSH antibodies, showed no changes of clinical relevance. Analysis of serum FSH levels revealed comparable elimination half-lives of 44 Ϯ 14 (mean Ϯ SD) and 32 Ϯ 12 hours in women and men volunteers, respectively. In contrast, peak FSH concentrations were significantly lower in women than in men volunteers (4.3 Ϯ 1.7 versus 7.4 Ϯ 2.8 IU/L), and the time required to reach peak levels of FSH was significantly longer in women than in men (27 Ϯ 5 versus 14 Ϯ 8 hours). The area under the serum level versus time curve tended to be smaller in women than in men volunteers (339 Ϯ 105 versus 452 Ϯ 183 IU/L ϫ hours), but the difference did not reach statistical significance. Together these data suggest that recombinant FSH is absorbed from its intramuscular depot to a lower rate and extent in women than in men. In both sexes a relationship between serum FSH levels and body weight was apparent. During the experimental period, other hormones remained low at baseline levels or were only slightly increased. Conclusion(s):Our findings indicate that recombinant FSH is well tolerated and that it is absorbed from its intramuscular depot to a higher rate and extent in men than in women. After intramuscular administration, its half-life is in good agreement with that previously reported for natural FSH. (Fertil Steril 1993;59:108 -14.

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“…For a long time, this functional role of the microvasculature in the human testis was neglected. During the past decade, the testicular microvasculature has attracted attention because of its assumed modulation by endocrine and paracrine mechanisms that are important for the regulation of spermatogenesis (Bergh et al 1988;Damber et al 1987Damber et al , 1989Sharpe 1990;Setchell 1990;Bergh and Damber 1992). This is supported by the detection of androgen receptors on the arterial side of the microvasculature and of estrogen receptors in the vasculature of the human testis (Ergün and Ungefroren 1995).…”

Section: Introductionmentioning

confidence: 95%

Capillaries in the lamina propria of human seminiferous tubules are partly fenestrated

Ergün

Davidoff

Holstein

1996

Cell and Tissue Research

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The three capillary parts of the microvasculature of the human testis, namely the arterial side inter-Leydig cell capillaries, the intramural capillaries, and the venous side inter-Leydig cell capillaries, were studied in detail by dual detection of alkaline phosphatase enzyme activity and endothelial marker immunoreactivity, and by means of light- and transmission-electron microscopy. Alkaline phosphatase enzyme activity was seen in intertubular arterioles, capillaries, and venules, and in intramural capillaries of the human testis, whereas the lamina propria of human seminiferous tubules showed no staining. Alkaline phosphatase enzyme activity and the endothelial marker detected by the Qbend 30 antibody co-existed within the endothelial cells of the microvasculature. Electron-microscopically, the endothelial cells of the arterial and venous side inter-Leydig cell capillaries, and of the intertubular capillaries free of Leydig cells were of the continuous type without fenestrations (A-1-alpha type). The intramural capillaries consisted of non-fenestrated (A-1-alpha type) and fenestrated sections (A-2-alpha type). The fenestrations faced the germinal epithelium. Capillaries with a continuous non-fenestrated endothelium contained a large number of transcytotic vesicles and channels. These were numerous in the endothelial cells of the inter-Leydig cell capillaries and the non-fenestrated part of the intramural capillaries. Capillaries partly ran in between the layers of the lamina propria and therefore represented the capillarization of the seminiferous tubules. Thus the multilayered lamina propria probably requires its own capillary supply to allow rapid exchange between the microvasculature and the epithelium of the human seminiferous tubules.

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Intratesticular Control Of Steroidogenesis

Cited by 84 publications

References 106 publications

Mediation of seasonal testicular regression by apoptosis

Mediation of seasonal testicular regression by apoptosis

Single-Dose Pharmacokinetics and Pharmacodynamics of Recombinant Human Follicle-Stimulating Hormone (Org 32489) in Gonadotropin-Deficient Volunteers

Capillaries in the lamina propria of human seminiferous tubules are partly fenestrated

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