Effect of Urotensin I on the ionic content of the plasma and the Gallbladder bile of Hoplias malabaricus (Bloch, 1974) (Teleostei, Characiformes, Erythrinidae)

Abstract

In this study the urotensin I (UI) effect on the ionic content of the plasma and the gallbladder bile (GB) of Hoplias malabaricus, a freshwater teleost, was investigated, and action of this hormone on the water trasnport in the gallbladder was analyzed. Fishes were captured in ponds situated on the campus of the Federal University of Santa Maria (UFSM), Santa Maria, Southern Brazil. Blood was collected by puncture of caudal artery and GB was drained by the cystic duct. The intraperitoneal injection of UI (500 ng/kg) in H. malabaricus increased the Na+ levels in the plasma and in the GB in relation to the saline-injected group. However, no change was observed in the levels of K+, Ca++ and Mg++ in the plasma and in the GB when UI was injected. The gallbladder of H. malabaricus has a mucosa-serosa water flow. On incubation of the serosa of the gallbladder sacs with UI (10-8M) there was a significant increase in water flow. Due to the fact that UI alters the GB Na+ levels and the water flow in the gallbladder, it is possible that UI can be involved in the regulation of the bile composition on fishes.

Ion levels in the gastrointestinal tract content and plasma of four teleosts with different feeding habits

“…In traira, the levels of Na + and Cl ) in the plasma were similar or slightly higher (around 10%) than those determined in specimens maintained for several days in the laboratory, but the plasma levels of other ions were similar (Baldisserotto et al 1996a;Baldisserotto and Mimura 1997). In the silver catfish used in the present study, the levels of plasma Na + were higher and those of Clwere lower than those determined by Borges et al (2004) in a study on silver catfish kept in the laboratory for 3 days; those of other ions were similar.…”