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

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)