Presence of immunoreactive corticotropin-releasing factor in rat testis

We attempted to demonstrate the presence of immunoreactive (ir) CRF in rat testis by RIA, and by an immunocytochemical technique. The RIA was performed on 27,000 x g supernatants of phosphate buffer extracts of adult rat testes, and revealed a high concentration of irCRF (51 - 74 ng/g testis), with a clear parallelism to the standard curve prepared with synthetic rat CRF. In contrast, the peripheral blood level of irCRF was extremely low (less than 0.05 ng/ml). Immunocytochemical studies of irCRF revealed strong specific staining in the Leydig cells and germ cells in normal adult rat testis. Epididymal spermatozoa also stained positive. Testicular irCRF fluctuated significantly with age. The levels (mean +/- SD) assayed in 10, 20, 60 and 90-day-old rats were 41.6 +/- 4.7, 8.7 +/- 0.2, 55.5 +/- 3.3 and 71.3 +/- 3.4 ng/g testis, respectively (P less than 0.01). The level was drastically reduced after abdominal translocation of a testis (9.6 +/- 1.3 ng/g testis), and after hypophysectomy (16.7 +/- 1.6 ng/g testis) in adult rats. However, neither hemicastration nor unilateral cryptorchidism influenced the irCRF levels in the contralateral testis. These data suggest a local production of irCRF which may play a role in regulation of Leydig cell function and sperm maturation in testis and epididymis.