Prolonged suppression of spermatogenesis by oestrogen does not preserve the seminiferous epithelium in procarbazine‐treated rats

Morris²

1993

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The epidermal growth factor (EGF) receptor is expressed in a wide variety of cell types and is known to be present in the testis of many species including man. In the present study, specific 125I-labelled EGF binding was observed in isolated interstitial cell preparations from both the intact and Leydig cell-depleted rat testis. It was demonstrated that the population of cells to which 125I-labelled EGF binds has a different buoyant density from either of the two adult Leydig cell populations, and remains unchanged in the absence of Leydig cells following in-vivo treatment with ethane dimethane sulphonate (EDS). Cells of this density (1.064 g/ml) identified by electron microscopy were fusiform mesenchymal cells, identical to those suggested by others to be able to differentiate into Leydig cells in vitro, i.e. Leydig cell precursors. In a culture system using two interstitial cell preparations of different buoyant densities from immature rats, both EGF and transforming growth factor-alpha (TGF-alpha) caused increased [3H]thymidine incorporation in the less dense cell preparation. TGF-alpha was more potent than EGF. EGF increased testosterone production in both fractions in amounts which could be related to the amount of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD)-positive cells. This study demonstrated that rat Leydig cells (defined as those cells which bind 125I-labelled human chorionic gonadotrophin, have distinct buoyant densities, are 3 beta-HSD positive and are sensitive to EDS), do not bind 125I-labelled EGF. Rather, EGF binds to a mesenchymal cell without LH receptors which is resistant to EDS.(ABSTRACT TRUNCATED AT 250 WORDS)

Section: Methodsmentioning

confidence: 99%

Paracrine effects via the epidermal growth factor receptor in the rodent testis may be mediated by non-Leydig interstitial cells

Morris²

1993

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“…Testosterone was measured in the culture fluid using a previously described RIA (Morris et al 1990). The sensitivity of the assay was 0-16 ng/ml and the intraassay coefficient of variation was 3%.…”

Section: Ria Of Testosteronementioning

confidence: 99%

The involvement of insulin-like growth factor-I in local control of steroidogenesis and DNA synthesis of Leydig and non-Leydig cells in the rat testicular interstitium

Morris²

1993

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Insulin-like growth factor-I (IGF-I) peptide, receptors and binding proteins are present in the rodent testis, which strongly implies that IGF-I has one or more testicular functions. In the present study we provide further information to support the concept that IGF-I is an important local mediator in the testis. High concentrations of IGF-I were measurable in interstitial fluid by radioimmunoassay, and IGF-I-binding proteins (IGFBPs) were readily detectable in interstitial fluid by ligand blotting, the predominant type being IGFBP-2. In vitro, IGF-I bound to testicular interstitial cells which did not have 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity and which were resistant to ethane dimethanesulphonate treatment. In vitro, IGF-I receptor-mediated actions increased both steroidogenesis and DNA synthesis. Insulin stimulated DNA synthesis at concentrations appropriate to cross-react with the IGF-I receptor, and this effect was greater in a testicular interstitial Leydig cell-depleted cell population compared with a Leydig cell-enriched cell culture. Furthermore, combinations of epidermal growth factor or transforming growth factor -alpha together with insulin appeared to act synergistically, causing extremely large increases in [3H]thymidine incorporation in the interstitial cells. These results support a paracrine and/or autocrine role for IGF-I in interstitial cell growth and development.

“…This dose was chosen on the basis of previous experiments in which hCG has been shown to stimulate Leydig cell activity (Chemes et al 1976;Christensen & Peacock, 1980). (2) Silastic capsules (Dow Corning Corpora¬ tion, Midland, MI, U.S.A. ; internal x external diame¬ ter x length = 2-6 mm 4-9 mm 5 mm for immature rats or 25 mm for adult rats) containing oestradiol-17ß were implanted s.c. and the rats were used after 7 days (Morris, Bardin, Gunsalus & Ward, 1990). The dimensions of the capsules were chosen to deliver pharmacological concentrations of oestradiol which would atrophy the testis and inhibit the activity of the Leydig cell.…”

mentioning

confidence: 99%

In-vitro DNA synthesis in Leydig and other interstitial cells of the rat testis

Findlay²,

Morris³

1992

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Replicative DNA synthesis (125I-labelled iododeoxy-uridine incorporation) was measured in interstitial cells prepared from rat testes and separated by Percoll density gradient centrifugation. Leydig cells were identified by 125I-labelled human chorionic gonadotrophin (hCG) binding and 3 beta-hydroxysteroid dehydrogenase histochemistry. Continuous density gradients indicated that interstitial cell DNA synthesis was not associated with Leydig cells, and was greater in cells from the immature than from the mature rat testis. Fractionation of cells by discontinuous density gradients into Leydig cell-rich and -depleted pools did not result in a similar enrichment of DNA synthesis. Treatment of the adult rat with hCG increased DNA synthesis into both fractions but oestrogen had no effect. DNA synthesis was greater in cells from the immature rat but, in contrast to the adult, in-vivo hCG treatment had no effect, whilst oestrogen decreased synthesis. To characterize the cells synthesizing DNA further, interstitial cells were prepared from testes in which the Leydig cells were depleted by in-vivo treatment with ethane dimethanesulphonate (EDS) or depleted in their germ cells by treatment in utero with busulphan. EDS treatment had no effect on DNA synthesis by the interstitial cells in spite of the 125I-labelled hCG binding being markedly reduced. Similarly, busulphan treatment was also without effects upon DNA synthesis. Fluorescence-activated cell cycle analysis of cells from both fractions from germ cell-depleted testes indicated that only a small proportion (3%) of the interstitial cells were actively dividing and this was almost doubled in cells from the germ cell-depleted immature rat testes.(ABSTRACT TRUNCATED AT 250 WORDS)