Inhibition of CRF- and urotensin I-stimulated ACTH release from goldfish pituitary cell columns by the CRF analogue alpha-helical CRF-(9-41)

alpha-Helical CRF-(9-41) is an analogue of corticotropin-releasing factor (CRF) that antagonizes CRF-stimulated ACTH release in rats. In the present study, alpha-helical CRF-(9-41) was tested to determine whether it would antagonize the ACTH-releasing activity of CRF or urotensin I (UI) observed with superfused, dispersed goldfish anterior pituitary cells. At a concentration of 4 microM, alpha-helical CRF-(9-41) completely blocked the ACTH-releasing activity of 100 nM CRF or 100 nM UI. The inhibitor by itself showed little intrinsic ACTH-releasing activity. This investigation reveals similarities in the CRF-antagonism of alpha-helical CRF-(9-41) in the teleost and mammalian pituitary in vitro. It also provides are similar and suggests that alpha-helical CRF-(9-41) may be useful as a tool to investigate the effects of CRF-like and UI-like peptides in teleost fishes.