Influence of rat testicular macrophages on Leydig cell function in vitro

The influence of co-cultures of rat testicular macrophages and Leydig cells (LC) on LC morphology and steroidogenesis was investigated with and without macrophage stimulation by a bacterial lipopolysaccharide (LPS). LC showed an elongated form in the presence of stimulated testicular macrophages. In the presence of non-stimulated testicular macrophages a significant inhibition of testosterone production was observed (decrease of 33%) from 48 h in co-culture while an increase of 16% was obtained at the same culture time, after stimulation of macrophages by LPS. When LC were treated with testicular macrophage-conditioned media (MCM) obtained from LPS-treated macrophages, they became fusiform and there was stimulation (78%) of steroid production. After human FSH stimulation (1-1000 mIU ml-1), MCM from testicular macrophages was no more effective in enhancing testosterone production by LC than was media from untreated LC. Similar experiments with LPS were conducted with macrophages of peritoneal origin. Peritoneal macrophages stimulated or not by LPS in co-cultures with LC or peritoneal MCM did not significantly modify testosterone production. However, these cells were able to modify LC morphology when LPS-MCM was added to LC-culture medium. The present results suggest strongly that testicular macrophage-LC interactions could be important in the control of LC steroidogenesis.