Effects of teleost urotensins on intestinal absorption of water and NaCl in tilapia, Sarotherodon mossambicus, adapted to fresh water or seawater

Abstract

Urotensins I (UI) and II (UII), peptides released from the teleost urophysis, have been implicated in teleost osmoregulation. The effects of these peptides on intestinal absorption in tilapia are examined in vitro using anterior intestinal segments of freshwater (FW)- and seawater (SW)-adapted fish. Intestinal sacs are incubated with 10- and 20-mU/ml concentrations of semipurified Gillichthys UI or UII. UI causes significant decreases in water and NaCl absorption in FW fish but has no effect in SW fish. On the other hand, UII has no effect on FW fish but increases water and NaCl absorption in SW fish. The results suggest that the effects of UI on intestinal transport may be important in FW fish, whereas those of UII may be advantageous to SW fish. The anteriorintestine joins the urinary bladder, skin, and opercular membrane as a possible locus of action of the urotensins.