Photoperiodic modulation of testicular LH receptors in the bank vole (Clethrionomys glareolus)

Tähkä, K. M.; Rajaniemi, Hannu

doi:10.1530/jrf.0.0750513

Cited by 14 publications

(1 citation statement)

References 26 publications

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“…In this study, the high testosterone secretion in High-T bulls was associated with increased concentrations of testicular LH receptors as well as an increase in testis size and basal concen¬ trations of serum LH and FSH. Increases in testicular LH/hCG receptor binding during the breed¬ ing season in the mongoose (Herpestes auropunctatus) (Soares & Hoffman, 1982a) and sheep (Barenton & Pelletier, 1983), or experimentally induced stimulatory photoperiods in hamsters (Bartke et al, 1982) and bank voles (Clethrionomys glareolus) (Tahka & Rajaniemi, 1985) have been related to increased androgen production (Bartke et al, 1982;Barenton & Pelletier, 1983;Tahka & Rajaniemi, 1985). These results are therefore consistent with findings that seasonal patterns of testosterone secretion are due, in part, to altered testicular sensitivity to LH.…”

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confidence: 79%

Impact of season on seminal characteristics and endocrine status of adult free-ranging African buffalo (Syncerus caffer)

et al. 1991

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Pituitary, gonadal and adrenal activity were compared in free-living, adult African buffalo bulls during the breeding and nonbreeding seasons. Frequent blood samples were collected for 2 h from anaesthetized bulls treated intravenously with saline, gonadotrophin-releasing hormone (GnRH, 200 micrograms), human chorionic gonadotrophin (hCG, 10,000 i.u.) or adrenocorticotrophic hormone (ACTH, 1.5 mg). Electroejaculates also were collected from anaesthetized bulls during the breeding and nonbreeding seasons. Pretreatment testosterone concentrations among bulls varied more during the breeding (0.17-23.0 ng/ml) than the nonbreeding (0.15-2.21 ng/ml) season. The variation within the breeding season was attributed to 8 of 25 bulls producing higher (P less than 0.05) serum testosterone (High-T; 16.28 +/- 2.03 ng/ml) and testicular LH receptor (1.53 +/- 0.22 fmol/mg testis) concentrations compared with their seasonal counterparts (Low-T; 0.95 +/- 0.26 ng/ml; 0.38 +/- 0.04 fmol/mg) or with all bulls during the nonbreeding season (0.90 +/- 0.27 ng/ml; 0.31 +/- 0.04 fmol/mg). The magnitude of GnRH- and hCG-induced increases in serum testosterone was similar (P greater than 0.05) between Low-T bulls and bulls during the nonbreeding season. In the High-T animals treated with GnRH or hCG, serum testosterone did not increase, suggesting that secretion was already maximal. Peak serum LH concentrations after GnRH were greater (P less than 0.05) in bulls during the nonbreeding than the breeding season; FSH responses were similar (P greater than 0.05). ACTH treatment did not increase serum cortisol concentrations above the 2-fold increase measured in bulls treated with saline, hCG and GnRH (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Discussionsupporting

confidence: 79%

Impact of season on seminal characteristics and endocrine status of adult free-ranging African buffalo (Syncerus caffer)

et al. 1991

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Influence of Photoperiod, Ambient Temperature and Melatonin on Testosterone Synthesis and Release During Reproductive Maturation in Male Deer Mice

Fail

Whitsett

1988

Journal of Andrology

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Four experiments were designed to investigate the influence of photoperiod and other environmental factors on androgen production and reproductive maturation in deer mice. Male prairie deer mice (Peromyscus maniculatus), born in a light/dark cycle of 6L:18D, either remained in this short photoperiod or were switched to a long day regimen of 16L:8D at weaning. In a cross-sectional experiment, the deer mice were killed between 3 and 8 weeks of age for measurement of serum testosterone concentration and reproductive organ weights. In a second experiment, blood was collected from each mouse at weekly intervals between 3 and 9 weeks of age. This repeated measures design was used to reduce the high variability in testosterone values observed in the first experiment. Reproductive organs were weighed at the termination of the experiment. Testosterone concentrations and reproductive organ weights were greater in males reared in the long photoperiod in both experiments. In a third experiment, the animals were housed under five different conditions to test the influence of high ambient temperature and melatonin as well as photoperiod. At 7 weeks of age, they received an injection of hCG or saline. More testosterone was released in deer mice reared in 16L:8D and 27 C than in those reared in short days (6L:18D) or those reared in high ambient temperature (35 C) or those treated with exogenous melatonin. One week later, animals were sacrificed. The single hCG treatment caused significant reversal of the suppression of accessory sex organ weights following melatonin, short days or 35 C temperature. In a fourth experiment, the additive influence of melatonin and 35 C temperature was tested. Animals treated with 35 C or both melatonin and 35 C had lower serum testosterone at 7 weeks of age, released less testosterone after hCG, and had smaller organ weights with or without hCG than long day controls. The influence of melatonin treatment and 35 C temperature appears to be additive for testicular weight and testosterone release after hCG. Thus, the attenuation of reproductive development that accompanied short days, melatonin treatment and high ambient temperature occurred via diminished testosterone secretion, which can be overcome at least in part by gonadotropin treatment.

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Seasonal modulation of androgen synthesis in the mink (Mustela vison) is associated with qualitative changes in testicular steroidogenesis in vitro

Tähkä¹,

Teräväinen

Sundqvist

1991

J. Exp. Zool.

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Annual changes in testicular weight and microsomal androgen synthesis were studied in the mink (Mustela uison). Testicular samples were taken at different phases of the annual reproductive cycle. Steroidogenesis was assessed by investigating seasonal differences in the testicular conversion of [4-14Clpregnenolone (PI and [4-14Cldehydroepiandrosterone (DHA) to metabolites in vitro. The steroid metabolites were identified by thin-layer chromatography. Seasonal changes in the capacity of the testis to produce testosterone from DHA and P correlated positively with the annual reproductive cycle of the species as well as with our earlier findings on plasma testosterone levels. Although the percentage conversion to testosterone (T) from both substrates decreased (39.8% to 19%, DHA; 33% to 15.5%, P) during testicular regression, the in vitro production of androstenedione (A) was increased. The A/T ratio changed from 0.32 (DHA) and 0.42 (P) during testicular activation in November to 1.9 (DHA) and 2.52 (P) during regression

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Photoperiodic modulation of testicular LH receptors in the bank vole (Clethrionomys glareolus)

Abstract: Summary. The

Cited by 14 publications

References 26 publications

Impact of season on seminal characteristics and endocrine status of adult free-ranging African buffalo (Syncerus caffer)

Impact of season on seminal characteristics and endocrine status of adult free-ranging African buffalo (Syncerus caffer)

Influence of Photoperiod, Ambient Temperature and Melatonin on Testosterone Synthesis and Release During Reproductive Maturation in Male Deer Mice

Seasonal modulation of androgen synthesis in the mink (Mustela vison) is associated with qualitative changes in testicular steroidogenesis in vitro

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