Immunomodulatory role of urotensins in teleost Channa punctatus.

The present study, for the first time in ectothermic vertebrates, reports the immunoregulatory role of urotensins I and II (UI and UII). Urotensins decreased the phagocytosis and nitrite production by splenic phagocytes. On superoxide production, UI had stimulatory while UII showed inhibitory effect. UI exerted its effect on phagocytes through corticotrophin-releasing factor (CRF) receptor as its non-specific antagonist astressin completely blocked the effect of UI on phagocytosis, nitrite release and superoxide production. Among the antagonists for specific CRF receptor 1 and 2, only CRF receptor 1 antagonist NBI 27914 abolished the effect of urotensin I. On the other hand, UII mediated its effect through urotensin receptor (UT receptor) since its antagonist urantide antagonized the effect of UII on phagocytosis, superoxide and nitrite release. These findings provide the direct evidence on physiological role of UI and UII through CRF receptor 1 and UT receptor, respectively in control of fish immune responses.