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  • Author: G. P. Risbridger x
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G. F. Gonzales, G. P. Risbridger and D. M. de Kretser


The effect of epidermal growth factor (EGF) on the production of immunoreactive inhibin by adult rat isolated seminiferous tubules in vitro has been investigated. EGF (0·1–1000 ng/ml) added to cultures of seminiferous tubules from adult rats caused a dose-dependent increase in inhibin content in the tubules without changing the amount secreted into the media. However, after continuous stimulation with EGF for periods in excess of 5 days, an increase in inhibin secretion was observed. In the presence of 10 and 100 ng FSH/ml, EGF (10 ng/ml) produced a further increment in the inhibin content of the tubules, but this effect was not found with FSH concentrations of 500 or 1000 ng/ml. EGF also increased the tubule content of inhibin after the addition of 100 μg dibutyryl cyclic AMP/ml but no effect of EGF was observed on the FSH- or dibutyryl cyclic AMP-induced secretion of inhibin into the medium.

The effect of EGF on inhibin content in the tubules was partially suppressed by the addition of 4β-phorbol-12β-myristate-13α-acetate (20 ng/ml). Insulin (1–100 ng/ml) decreased basal inhibin secretion without changing the inhibin content of tubules and this effect was antagonized by EGF (10 ng/ml) with insulin doses of 1–50 ng/ml whereas, at 100 ng/ml, the effect of EGF on tubule inhibin content was reversed. The addition of EDTA (2 mmol/l) resulted in an inhibition of basal and EGF-induced inhibin production. These data demonstrate a stimulatory effect of EGF on inhibin production by isolated seminiferous tubules which is inhibited by insulin and phorbol esters, both stimulators of protein kinase C activity.

Journal of Endocrinology (1989) 123, 213–219

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G. P. Risbridger, J. B. Kerr and D. M. de Kretser


Leydig cells were selectively eliminated from the testis by treatment with the cytotoxin, ethane dimethane sulphonate. Rats were then made unilaterally cryptorchid and the morphological and functional response of the interstitial tissue in abdominal compared with scrotal testes was examined for up to 8 weeks. Regeneration of new Leydig cells occurred more rapidly in the interstitial tissue of abdominally cryptorchid testes compared with the interstitial tissue of contralateral scrotal testes. More rapid recovery of Leydig cells was coincident with significant increases in the bioactivity of a local factor(s), collected from interstitial fluid of cryptorchid testes, which stimulated testosterone production by isolated Leydig cells in vitro. These results support the theory that the production of a local factor(s) plays a role in the regeneration of Leydig cells and is affected by damage to the seminiferous epithelium.

J. Endocr. (1987) 112, 197–204

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G P Risbridger, T Thomas, C J Gurusinghe and J R McFarlane


Inhibin and activin are members of the transforming growth factor β (TGFβ) family which can regulate cell proliferation in a number of tissues. The presence of inhibins and the related proteins, activins, in the prostate has been implicated by the detection of activin type II receptors. The aim of this study was to determine whether or not immunoactive (ir) inhibin and ir-activin are present in the rat prostate and to study the acute regulation by androgens. The results showed that mRNAs for the α and β inhibin subunits were detected in rat prostate by reverse transcription-PCR together with ir-inhibin and ir-activin in prostate cytosols. The levels of ir-activin in the prostate (223 ± 44 ng/gland) were greater than the levels of ir-inhibin (6·89 ng/gland), and activin immunoreactivity was localised to the epithelial cells. The presence of these proteins and the subunit mRNAs suggests that these proteins are produced in the prostate and may have a role in prostate function. The study of the effect of androgen withdrawal on the levels of ir-activin and ir-inhibin in these tissues showed no change in the content of ir-inhibin or ir-activin (ng/g tissue) after 3 days of castration or following the administration of the cytotoxic drug ethane dimethane sulphonate (EDS), although there was a significant (P<0·01) decline in prostate weight. Fourteen days after EDS treatment, as the prostate weight fell significantly lower, the amount of ir-inhibin and ir-activin per prostate gland was significantly (P<0·01) reduced although the concentration was unaffected. These data demonstrate, for the first time, that inhibin α and β subunit mRNA and ir-inhibin and ir-activin are present in the prostate; the role of these proteins in prostate function remains to be established.

Journal of Endocrinology (1996) 149, 93–99