In vitro metabolization of (14C) testosterone by spermatogenic tissue and the accessory gland of Blennius pavo (Blenniiformes, Teleostei)

The male gonad of blenniid fishes consists of two separate parts, a larger spermatogenic portion and a relatively small accessory gland. Within that glandular portion are scattered clusters of cells which are considered to correspond to mammalian Leydig cells. In this study spermatogenic and glandular tissue of Blennius pavo were incubated separately with labelled testosterone in vitro. The proportions of metabolites produced by both types of tissue differ greatly. In the spermatogenic section reductive metabolization predominates whereas in the glandular part a higher share of Δ4-steroids is noticeable. Among these, 11-oxygenated compounds represent quantitatively the most important part. This observation is the more striking as the mass of glandular tissue which the incubations had to be carried out was considerably smaller. It is concluded that a distinct qualitative difference exists between steroid producing interstitial cells in the two components of the male gonad of this fish. On these grounds problem of 'homology' between mammalian Leydig cells and interstitial cells in teleosts is discussed. (author). 17 refs