Cholinergic inhibition of urinary acidification by the turtle bladder
| Autor: | Jose A.L. Arruda, Sandra Sabatini, with the technical assistance of George Dytko, Roger Mola, Jell Hseih |
|---|---|
| Jazyk: | angličtina |
| Předmět: |
Atropine
medicine.medical_specialty Pentobarbital Carbachol Urinary Bladder chemistry.chemical_element Calcium Lanthanum Internal medicine Muscarinic acetylcholine receptor medicine Extracellular Animals Secretion Cyclic GMP Hydrogen-Ion Concentration Turtles Endocrinology chemistry Parasympathomimetics Nephrology Cholinergic medicine.drug |
| Zdroj: | Kidney International. (5):622-630 |
| ISSN: | 0085-2538 |
| DOI: | 10.1038/ki.1980.73 |
| Popis: | Cholinergic inhibition of urinary acidification by the turtle bladder. The effect of carbachol on urinary acidification by the turtle bladder in vitro was studied. Carbachol inhibited urinary acidification in a dose-dependent fashion, with half maximal inhibition occurring at 4.5 × 10 -5 M. The effect of carbachol on urinary acidification could be totally prevented by atropine, indicating that the inhibition is mediated through a muscarinic receptor. Carbachol inhibited hydrogen ion secretion by decreasing the active proton conductance and not by altering the proton motive force. Carbachol failed to increase passive loss of hydrogen ion from the mucosa. Carbachol increased calcium uptake by the turtle bladder; this increase in calcium uptake could be prevented by pretreatment with atropine, pentobarbital, or lanthanum. Pentobarbital or lanthanum blunted the inhibitory effect of carbachol on hydrogen ion secretion. In the presence of low extracellular calcium (0.2 mM), carbachol failed to increase calcium uptake but caused a significant inhibition of hydrogen ion secretion. In the presence of normal calcium concentration, carbachol caused a significant efflux of calcium. These data demonstrate that carbachol inhibits urinary acidification and suggest that the mechanism of this inhibition may be related, at least in part, to changes in cytosolic calcium. Inhibition cholinergique de l'acidification urinaire par la vessie de tortue. L'effet du carbachol sur l'acidification urinaire par la vessie de tortue in vitro a ete etudie. Le carbachol inhibe l'acidification urinaire, l'inhibition est dose dependante et la demi-inhibition maximale est obtenue a 4,5 × 10 -5 M. L'effet du carbachol sur l'acidification urinaire peut etre completement empeche par l'atropine, ce qui indique que l'inhibition a pour mediateur un recepteur muscarinique. Le carbachol inhibe la secretion d'ions de hydrogene en diminuant la conductance et non en modifiant la force cinetique. Le carbachol n'a pas augmente la perte passive d'ions de hydrogene par la muqueuse. Le carbachol a augmente la captation de calcium par la vessie de tortue. Cette augmentation peut etre empechee par un pretraitement par l'atropine, le pentobarbital ou le lanthane. Le pentobarbital ou le lanthane masquent l'effet inhibiteur du carbachol sur la secretion d'ions de hydrogene. En presence d'une concentration extracellulaire de calcium faible (0,2 mM), le carbachol n'a pas augmente la captation de calcium, mais a determine une inhibition significative de la secretion d'ions de hydrogene. En presence d'une concentration normale de calcium le carbachol entraine un efflux significatif de calcium. Ces resultats demontrent que le carbachol inhibe l'acidification urinaire et suggere que le mecanisme de cette inhibition peut etre en rapport, au moins partiellement, avec des modifications du calcium cytosolique. |
| Databáze: | OpenAIRE |
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