The actions of corticotropin-releasing hormone (CRH) on steroidogenesis in enriched preparations of mouse and rat Leydig cells were investigated. Primary cultures of purified Leydig cells as well as a Leydig tumor cell line were used in these studies. CRH had a stimulatory effect on steroid production in both isolated preparations of mouse Leydig cells (80-90% Leydig cells) and MA-10 cells (a mouse Leydig tumor cell line). In primary cultures of mouse Leydig cells, CRH was effective over a range of 1 nM-100 nM, while MA-10 cells were responsive over a wider range (10 nM-100 μM). When a submaximal dosage of CRH was given together with a maximal dosage of hCG, steroid production was stimulated even more highly in MA-10 cells. However, when primary cultures of mouse Leydig cells were treated with CRH and hCG, no similar response was observed. In addition, a CRH antagonist, α-helical CRH9-41, reversed the CRH stimulatory effect on steroidogenesis in both mouse Leydig cells and MA-10 cells. The accumulation of intracellular cAMP after CRH treatment was dose-responsive to CRH in both cell types, a finding similar to the results described above for steroid production. CRH had no effect on steroidogenesis in rat Leydig cells (60- 80% Leydig cells) in the present study. These results indicate that mouse Leydig cells respond to CRH through specific receptors with increased production of cAMP and steroids.
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