Increased testosterone production in vitro by Leydig cells from rats with severe autoimmune orchitis.

We have previously observed (M. O. Suescun et al., 1994, Journal of Andrology, 15, 442-448) that rats with autoimmune orchitis (EAO) exhibit increased testosterone production in vitro by isolated testes. The aim of the present study was to determine whether the increase in testosterone production correlated with an enhanced number of Leydig cells and/or enhanced steroidogenic capacity per Leydig cell. For this purpose, EAO was induced in adult Sprague-Dawley rats by active immunization with testicular homogenate and adjuvants. At 80 days after the primary immunization, 60% of rats presented with severe testicular damage characterized by sloughing of the seminiferous epithelium, seminiferous tubule atrophy and interstitial mononuclear cell infiltration. At 160 days after the first immunization, testicular lesions were more severe. A morphometric study, by light microscopy, showed an increase in the number of Leydig cells in rats with EAO (45% increase at 80 days and 50% at 160 days). By electronmicroscopy, testicular sections of rats with EAO revealed the presence of numerous Leydig cells closely associated with macrophages. Most Leydig cells exhibited ultrastructural features of active steroid secreting cells. The steroidogenic capacity of Percoll-purified Leydig cells from tests of rats with EAO, killed at 80 and 160 days, was evaluated. Leydig cells from rats with EAO exhibited an enhanced steroidogenic response to hCG in vitro at 80 days (38%) and an increase in basal (77%) and post-hCG testosterone production (115%) at 160 days compared to controls. However, these cells were less sensitive to hCG. In conclusion, the results indicate that the enhancement of in-vitro testosterone production observed in rats with EAO is accounted for both by the increased number of Leydig cells and by the increased testosterone production of each Leydig cell.