Activins and activin receptors in the rat testis

Inhibin and activin are gonadal protein hormones, which were originally defined by their negative and positive feedback action on the release of follicle stimulating hormone (FSH) from the pituitary gland. However, recent studies revealed that inhibin and activin do not only control FSH release but can also affect the functions of a large number of other cell types, as will be discussed in section 1.7. This section is preceded by short descriptions of the testicular cell types (section 1.2), the structures of inhibins, activins and other members of the TGF·-B family of growth and differentiation factors (sections 1.3 and 1.4), and of receptors and non-receptor binding proteins for inhibin and activin (sections 1.6 and 1.7). Finally, events occurring after binding of activin to its receptor are discussed in section 1.8. The aim of the experiments described in this thesis was the elucidation of intratesticular effects of activin. The expression of activin receptors, the secretion of activins and the effects of activins in the rat testis have been investigated.