Effect of oestradiol and tamoxifen on the testosterone response in male rats to a single injection of hCG

Hodgson, Yvonne; Urquhart, G.M.; Kretser, David M de

doi:10.1530/jrf.0.0680295

Cited by 9 publications

(8 citation statements)

References 25 publications

(29 reference statements)

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“…There was an abrupt increase in basal and hCG-stimulated testosterone production between 35 and 53 days of age, which is in keeping with the observation of Moger (1979) and Huhtaniemi et al (1982). At 53 days of age the in \ritro secretion of testosterone was significantly higher than that seen in adult testes (Hodgson & de Kretser 1983). This post pubertal decline in testicular production of testosterone has also been described in vitro by Sharpe & Fraser (1978).…”

Section: Discussionsupporting

confidence: 86%

The temporal response of rat testes to hCG stimulation during sexual maturation

Hodgson¹,

Kretser²

1984

Int J of Andrology

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Serum testosterone responses to a single sc injection of hCG (25 IU/100 g body weight) were monitored for 5 days in rats throughout sexual maturation (22-70 days). Two hours after hCG injection serum testosterone levels rose in 22, 37 and 53 day-old animals and remained elevated for 2 days, returning to control levels on day 3. This response differed markedly from the biphasic secretion of testosterone reported for adult animals. In 70 day-old animals the serum testosterone response approached that seen in adult animals. Testosterone levels were elevated 2 h after hCG injection (25.4 +/- 2.5 ng/ml) and declined significantly at 12 and 24 h to 17.1 +/- 1.0 and 16.1 +/- 3.4 ng/ml, respectively. Testosterone levels tended to increase again on days 2 and 3 (19.9 +/- 2.8 and 21.1 +/- 3.5 ng/ml, respectively) but the increase was not statistically significant. This response differed markedly to the biphasic secretion of testosterone reported for adult animals. In vitro patterns of basal and hCG-stimulated testosterone secretion by decapsulated testes following a single hCG injection also changed during sexual maturation. In 22 day-old animals the testes exhibited refractoriness to in vitro hCG stimulation at 12 h, but testes from 37 day old rats were refractory from 2 to 24 h. In vitro testosterone responses of testes from 53 and 70 day-old rats were similar to that reported for adult rats with a period of refractoriness from 12 h to 2 days. This study demonstrates that during sexual maturation in the rat alterations occur in the temporal patterns of testosterone secretion in vivo and in vitro following hCG stimulation.

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Section: Discussionsupporting

confidence: 86%

The temporal response of rat testes to hCG stimulation during sexual maturation

Hodgson¹,

Kretser²

1984

Int J of Andrology

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“…Nevertheless, it will be interesting to study the time course of the oestrogen response to hCG, to see whether it corresponds with the vascular response; it would seem more likely to follow the testosterone response. The time-course of the testosterone response to hCG shows some similarities to the results obtained by de Kretser (1982, 1984), Hodgson, Urquhart and de Kretser (1983) and Risbridger, Hodgson and de Kretser (1981).…”

Section: Discussionsupporting

confidence: 85%

The Increase in Testicular Vascular Permeabilty Induced by Human Chorionic Gonadotrophin Involves 5‐hydroxytryptamine and Possibly Oestrogens, but Not Testosterone, Prostaglandins, Histamine or Bradykinin

Sowerbutts

Jarvis

Setchell

1986

Aust J Exp Biol Med

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Summary. Possible intermediates in the response of the rat testicular vasculature to human chorionic gonadotrophin (hCG) have been investigated. Ketanserin, an antagonist of 5-hydroxytryptamine, significantly reduced the increase in 1-h albumin space seen 20 h after hCG, as did one aromatase inhibitor (l,4,6-androstatriene-3, 17-dione), but the effect of another (testolactone) did not reach significance. Aminoglutethimide, which inhibits overall steroid synthesis as well as aromatase, reduced the albumin space in both control and hCG-injected rats but the hCG response, as judged by the ratio between treated and control rats, was unaffected. Inhibitors of overall steroid synthesis (WIN 32,729), prostaglandin synthesis (meclofenamic acid or indomethacin) and angiotensin converting enzyme (captopril) and blockers of HI and H2 histamine receptors (mepyramine, cimetidine or ranitidine) were without effect. The time course of the vascular response to hCG is quite different from the response in testosterone secretion by the testis. Considerable numbers of mast cells were found in the vicinity of the testicular artery in the testicular capsule, and these may be a source of 5-hydroxytryptamine. INTRODUCTIONRecently, it was shown that a single injection of hCG into a male rat produced a striking increase in the permeability of the testicular blood vessels to albumin, in the amount of extracellular fluid in the testis and in testicular lymph flow (Setchell and Sharpe, 1981). For several reasons, it was suggested in that paper that hCG was not acting directly on the blood vessels, but rather that the effect was due to some testicular product whose formation was increased by hCG. Two obvious possibilities were oestrogens and prostaglandins. The present paper reports the results of a series of experiments designed to establish whether these or other possible vasoactive substances are involved in the hCG effect. While this paper was being written, the results of an independent study were published (Veijola and Rajaniemi, 1985), confirming our observations on the lack of effect of indomethacin and aminoglutethimide.

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“…We are unaware of any other species in which moment-to-moment changes in testicular vein steroid levels have been studied. Mean T levels rise -50% after acute human chorionic gonadotropin (hCG) stimulation in men (26), compared with 3-10-fold rises in experimental animals, including the rhesus monkey (23,27,28). Similarly, when LRH is administered to normal men, although pronounced increments in circulating LH levels occur, there are only slight increases in circulating T levels (1 1, 29).…”

Section: Discussionmentioning

confidence: 99%

Testosterone and estradiol are co-secreted episodically by the human testis.

Winters¹,

Troen²

1986

J. Clin. Invest.

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In spite of a striking pulsatile pattern of luteinizing hormone (LH) secretion, testosterone (T) fluctuations in peripheral blood in normal adult men are irregular and of low amplitude. To determine whether T secretion by the human testis is episodic, T was measured in blood samples drawn at 15-min intervals for 4 h through a catheter placed in the testicular vein of six men with varicocele-associated infertility. Estradiol (E2) concentrations were also determined in each sample. Each subject released testosterone in well-defined pulses. Gonadal vein T levels ranged from 1 to 1,540 ng/ml. Mean (±SE) pulse amplitude was 176±42 ng/ml, with a frequency of 4.0±03 pulses per 4 h. Testicular vein E2 levels ranged from 0.01 to 6.8 ng/ml. E2 secretory episodes were generally coincident with T pulses, and their amplitudes were highly positively correlated (r = 0.90, P < 0.01).These results indicate that T secretion by the adult human testis is pulsatile, and suggest a functional relationship between intermittent LH secretion and normal testicular steroidogenesis in men. The failure to appreciate these fluctuations as hormone pulses in peripheral blood may relate to their absolute amplitude and frequency. The concordance between E2 and T pulses suggests that the Leydig cell, under LH control, is the source of most of the E2 secreted by the adult human testis.

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Effect of oestradiol and tamoxifen on the testosterone response in male rats to a single injection of hCG

Cited by 9 publications

References 25 publications

The temporal response of rat testes to hCG stimulation during sexual maturation

The temporal response of rat testes to hCG stimulation during sexual maturation

The Increase in Testicular Vascular Permeabilty Induced by Human Chorionic Gonadotrophin Involves 5‐hydroxytryptamine and Possibly Oestrogens, but Not Testosterone, Prostaglandins, Histamine or Bradykinin

Testosterone and estradiol are co-secreted episodically by the human testis.

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