title: EFFECTS OF BARIUM CHLORIDE ON ELECTROLYTE TRANSPORT ACROSS ISOLATED COLONS FROM NORMAL AND ALDOSTERONE-TREATED LIZARDS (GALLOTIA GALLOTI)
abstract: Addition of BaCl2 to the solution bathing colons of normal lizards did not alter the absorptive Na+ flux, but did reverse the net absorption of Cl- to become net secretion. Cl- secretion resulted from an increase in its serosal-to-mucosal movement and was positively correlated to an increase in short-circuit current. Ba2+-induced short-circuit current was dependent on the presence of both Na+ and Cl- in the serosal medium. Ba2+-induced Cl- secretion could be reversed by serosal amiloride (10(&shy;4) mmol l-1). Colons from acutely or chronically aldosterone-treated lizards exhibited a considerably higher short-circuit current, potential difference and net Na+ absorption than did untreated colons. Net Cl- transport was unaltered by acute treatment, but was totally abolished after chronic treatment. BaCl2 rapidly decreased the potential difference, short-circuit current and tissue conductance across colons from aldosterone-treated lizards. Net Na+ transport was markedly inhibited by Ba2+ in both acutely and chronically treated tissues, but barium did not change unidirectional or net Cl- fluxes in these. The present results support the following hypotheses: (1) that BaCl2 inhibits electrogenic Na+ absorption induced by acute or chronic aldosterone treatment and (2) that Ba2+ induces an electrogenic Cl- secretion by stimulating a basolateral Na+-dependent Cl- intake in normal but not in aldosterone-treated colons. This also suggests that aldosterone could exert an antisecretory influence in colonic epithelia.
authors.initials: M
authors.lastname: D&Iacute;Az
authors.initials: A
authors.lastname: Lorenzo
authors.initials: T
authors.lastname: G&Oacute;Mez
authors.initials: P
authors.lastname: Bad&Iacute;A
authors.initials: A
authors.lastname: Bola&Ntilde;Os