Effect of urotensin II on water and ion fluxes in the intestine, Gallbladder and urinary bladder of the freshwater teleost, Hoplias malabaricus

Abstract

The effect of urotensis II (UII) on the flow of water and ions (Na+, K+, Ca2+ and Mg2+) in the medium intestine, rectum, gallbladder and urinary bladder of the freshwater teleost Hoplias malabaricus was investigated. The flow of water of all the studied organs of H. malabaricus is from mucosa to serosa (absorption). UII increased the flow of water in the medium intestine, gallbladder and urinary bladder. The medium intestine, gallbladder and urinary bladder also absorb Na+. K+ is absorbed in the rectum and secreted in the urinary bladder. UII did not affect the flow of Na+ and K+ in the studied portions. All studied portions secreted Ca2+, and UII reduced the fow of this ion in the medium intestine and urinary bladder. The flow of Ca2+ in the rectum and gallbladder was not altered by UII. There is no significant flow of Mg2+ in the studied portions, and UII stimulated the absorption of this ion in the medium intestine and urinary bladder. This study indicates that UII participates in the controlo f osmoregulatory organs of H. malabaricus. This study also raises the possibility that UII may be involved in the regulation of the composition of the bile fishesm, since it alters water and Ca2+ fluxes in the gallbladder of H. malabaricus.

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

“…In vitro experiments of intestinal portions of traira using the same solutions at both the mucosal and serosal sides showed water absorption and Ca 2+ secretion in the mid-and posterior intestine, respectively, and Na + and K + absorption in the mid-and posterior intestine, respectively, and no significant Mg 2+ absorption (Cl ) absorption was not studied) (Baldisserotto et al 1996b). This would explain the decrease in Na + levels and the fourfold increase in Ca 2+ levels in the fluid phase from the pyloric ceca to the posterior intestine.…”

“…The intestine also has to reabsorb ions discharged by gastric secretion (such as Cl ) ) (Hirano and Mayer-Gostan 1976) as well as by bile when fat enters the intestine. The intestine of several species of freshwater teleosts either absorbs (Smith 1964;Skadhauge 1969;Nakamura 1985;Baldisserotto et al 1996b) or does not transport K + (Dabrowski et al 1986;Baldisserotto et al 1993).…”

Ion levels in the gastrointestinal tract content of freshwater and marine–estuarine teleosts

“…The intestine also reabsorbs ions discharged by gastric secretion (such as Cl -) (Hirano and MayerGostan 1976) and bile when fat enters the intestine. The intestine of several species of freshwater teleosts either absorbs (Smith 1964;Skadhauge 1969;Nakamura 1985;Baldisserotto et al 1996) or does not transport K ? (Dabrowski et al 1986;Baldisserotto et al 1993).…”