[Immuno-endocrine interactions in the testis: possible involvement of Ca2+ in signal transduction pathway in Leydig...

The testis is divided, both functionally and anatomically, into two specialised compartments, i.e. the vascular interstitial tissue and avascular seminiferous tubules. Leydig cell steroidogenesis is mainly controlled by luteinizing hormone (LH) secreted from the anterior pituitary. It is well known that LH is able to generate second messengers by adenylate cyclase and the cycle of inositolphospholipids. Also Ca2+ ions are taken into account as an important modulators of Leydig cell steroidogenesis. The aim of this study was to show the effect of macrophage-conditioned medium on the basal and LH stimulated testosterone secretion by mouse Leydig cells in vitro. A source of Leydig cells was the testis of mature, Swiss strain mice. Leydig cells were isolated and cultured for 48 hrs. Testosterone levels were measured radioimmunologically. Intracellular free Ca2+ ions were analysed by computer automatic system 'MAGICAL'. Results indicated that not only LH but also macrophage-conditioned medium were able to modulate testosterone secretion by Leydig cells and increase intracellular calcium concentration. Therefore, it seems possible that the action of proteins secreted from macrophages is mediated through Ca2+ ions which are involved in another signal transduction pathway leading to stimulation of testosterone biosynthesis by Leydig cells in vitro.