A factor in spent media from Sertoli-cell-enriched cultures that stimulates steroidogenesis in Leydig cells.

We investigated whether Sertoli cell spent media (SCM) contain a factor (or factors) which influences steroidogenesis in Leydig cells. Freshly prepared prepubertal interstitial cells or Percoll-purified Leydig cells and similar cells cultured in the presence or absence of LH were incubated for 24 h in the presence of a 5 alpha-reductase inhibitor and in the presence or absence of SCM. The accumulation of C19-steroids (testosterone and androstenedione), C21-steroids (progesterone, 17 alpha-hydroxyprogesterone and 20 alpha-hydroxypregn-4-en-3-one) and cyclic AMP was measured by radioimmunoassay. It could be demonstrated that SCM contains a factor that stimulates an early step in the steroidogenic pathway but at the same time hampers the conversion of C21-precursors into androgens. In freshly prepared Leydig cells the final effect is a stimulation of the androgen output. In Leydig cells cultured in the absence of LH, mainly C21-steroid output is increased. These biological effects resemble those observed with LHRH and its agonists. The activity of the Sertoli cell factor is not affected by an LHRH antagonist, however, and maximally effective concentrations of the factor and LHRH have additive effects, suggesting that they act by distinct receptor systems. Preliminary characterization shows that the factor in SCM is a thermolabile protein with a MW greater than 10 000. The production of the factor decreases during prolonged culture in serum-free medium. Addition of fetal calf serum causes a marked and dose-dependent increase in the production or activity of the factor. Several permanent cell lines (B16, Bowes, BHK, Ratec, RK13, Vero) produce a factor with comparable biological effects on Leydig cells. Nonetheless, the observation that the production of this factor by Sertoli cell cultures is stimulated by FSH and dbcAMP suggests that, in the testis, it may play a role in the paracrine control of Leydig cell function.