Effect of cyclic AMP on acidification in the isolated turtle bladder.

Effect of cyclic AMP on acidification in the isolated turtle bladder. Cyclic AMP (10 mM) has been demonstrated to inhibit hydrogen ion secretion in the isolated turtle bladder. These experiments were designed to study the effect of cyclic AMP on hydrogen ion secretion in the isolated turtle bladder using both the pH stat and the reverse short circuit current techniques. Sodium transport was measured as the short circuit current. Studies were carried out at 0% CO 2 and 1% CO 2 at pH 7.4. Cyclic AMP (10 mM) was added to either the serosal or mucosal solutions, and hydrogen ion secretion was measured from 0 to 120 min. In the presence or absence of carbon dioxide, cyclic AMP and dibutyryl cyclic AMP had no effect on hydrogen ion secretion in fasted turtles. The addition of theophylline (10 mM) to the serosal solution, with or without cyclic AMP had no effect on proton secretion. Sodium transport was unchanged from control following serosal or mucosal addition of 10 mM cyclic AMP in the presence or absence of carbon dioxide. In chronically bicarbonate-loaded turtles proton secretion was the same as control fasted turtles. In these animals, however, serosal administration of 10 mM cyclic AMP significantly stimulated bicarbonate secretion. Stimulation of bicarbonate secretion occurred in the presence of a 20 mM bicarbonate gradient. When there was no bicarbonate gradient, cyclic AMP was without effect; cyclic AMP had no effect on bicarbonate permeability when measured in the presence of acetazolamide. These results indicate that cyclic AMP has no effect on hydrogen ion secretion or sodium transport in the isolated turtle bladder when studied at two different rates of acidification (0 and 1% CO 2 ). Cyclic AMP appears to stimulate active bicarbonate secretion. Effet de l'AMP cyclique sur l'acidification dans la vessie de tortue isolee. Il a ete montre que l'AMP cyclique (10 mM) inhibe la secretion d'ion hydrogene dans la vessie de tortue isolee. Ces experiences ont ete concues pour etudier l'effet de l'AMP cyclique sur la secretion d'ion hydrogene dans la vessie de tortue isolee, en utilisant des techniques de pH stat et de courant de court-circuit inverse. Le transport de sodium a ete mesure comme courant de court-circuit. Les etudes ont ete faites a 0% CO 2 et a 1% CO 2 a pH 7,4. L'AMP cyclique (10 mM) etait ajoute aux solutions sereuses ou muqueuses, et la secretion d'ions hydrogene etait mesuree de 0 a 120 min. En presence ou en l'absence de carbone dioxyde, l'AMP cyclique et le dibutyryl AMP cyclique n'avaient pas d'effet sur la secretion d'ions hydrogene chez les tortues a jeun. L'addition de theophylline (10 mM) a la solution sereuse, avec ou sans AMP cyclique, n'avait pas d'effet sur la secretion de protons. Le transport du sodium n'etait pas different du controle apres addition sereuse ou muqueuse de 10 mM d'AMP cyclique en presence ou en l'absence de carbone dioxyde. Chez des tortues en surcharge chronique en bicarbonates, la secretion de protons etait la meme que chez des tortues controles a jeun. Cependant, chez ces animaux l'administration sereuse de 10 mM d'AMP cyclique stimulait significativement la secretion de bicarbonates. La stimulation de la secretion de bicarbonate se produisait en presence d'un gradient de bicarbonate de 20 mM. Quand il n'y avait pas de gradient de bicarbonates, l'AMP cyclique etait sans effet; l'AMP cyclique n'avait pas d'effet sur la permeabilite aux bicarbonates mesuree en presence d'acetazolamide. Ces resultats indiquent que l'AMP cyclique n'a pas d'effet sur la secretion d'ions hydrogene ou sur le transport du sodium dans la vessie de tortue isolee, etudies a deux vitesses d'acidification differentes (0% et 1% de CO 2 ). L'AMP cyclique parait stimuler la secretion active de bicarbonates.