ACTH-releasing activity of urotensin I and ovine CRF: interactions with arginine vasotocin, isotocin and arginine vasopressin.

The release of ACTH from superfused dispersed goldfish anterior pituitary cells was examined to determine if the neurohypophyseal peptides arginine vasotocin (AVT), isotocin (IST) or arginine vasopressin (AVP) potentiate the ACTH-releasing activities of the structurally homologous peptides urotensin I (UI) or ovine corticotropin-releasing factor (CRF). The ACTH-releasing activities of the neurohypophyseal peptides and UI or CRF were additive. AVT, IST or AVP failed to potentiate the ACTH-releasing activity of UI or CRF. These results suggest that in teleost fishes neurohypophyseal peptides have intrinsic ACTH-releasing activity but, unlike mammals, do not potentiate the release of ACTH evoked by CRF, or by the piscian CRF-like peptide, UI.