Localization of sodium pump sites in frog urinary bladder.
Biochim Biophys Acta
; 375(2): 268-73, 1975 Jan 28.
Article
en En
| MEDLINE
| ID: mdl-123762
ABSTRACT
[3H]Ouabain binding in frog and toad urinary bladder was investigated by short-circuit current (SCC), scintillation counting and autoradiographic techniques. SCC data and analysis of tissue digests following serosal exposure to ouabain showed that ouabain binding and inhibition of Na+ transport was completely reversible in toad bladder whereas, in frog bladder, [3H]ouabain was tightly bound and Na+ transport remained suppressed even after a 60-min washout. Mucosal exposure of frog bladder to [3H]ouabain or serosal exposure after preincubation with unlabeled ouabain led to a marked reduction in binding. Specificity of binding was assessed further by adjusting the concentration of certain (Na+ -K+)-ATPase ligands(K+, ATP) to levels known to reduce ouabain binding. High K+ concentrations and depletion of endogenous ATP by incubation under anoxic conditions resulted in a significant drop in [3H]ouabain binding. Autoradiographic analysis showed that grains are localized primarily to the basolateral plasma membranes of the granular cells, providing direct morphological evidence for the location of Na+ pumps at these sites. Although autoradiographs did not provide sufficient resolution to rule out unequivocally ouabain binding to the mitochondria-rich cell, morphological evidence suggests that grain densities are significantly higher between adjacent granular cells than between granular cell-mitochondria-rich cell interfaces.
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Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Sodio
/
Vejiga Urinaria
Límite:
Animals
Idioma:
En
Revista:
Biochim Biophys Acta
Año:
1975
Tipo del documento:
Article