ISSN:
1432-1424
Keywords:
K+,Na+ transport
;
intracellular Ca2+
;
pH
;
membrane depolarization
;
quinine
;
quinidine
;
lidocaine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary 86Rb+ fluxes have been measured in suspensions of vesicles prepared from the epithelium of toad urinary bladder. A readily measurable barium-sensitive, ouabain-insensitive component has been identified; the concentration of external Ba2+ required for half-maximal inhibition was 0.6mm. The effects of externally added cations on86Rb+ influx and efflux have established that this pathway is conductive, with a selectivity for K+, Rb+ and Cs+ over Na+ and Li+. the Rb+ uptake is inversely dependent on external pH, but not significantly affected by internal Ca2+ or external amiloride, quinine, quinidine or lidocaine. It is likely, albeit not yet certain, that the conductive Rb+ pathway is incorporated in basolateral vesicles oriented right-side-out. It is also not yet clear whether this pathway comprises the principle basolateral K+ channel in vivo, and that its properties have been unchanged during the preparative procedures. Subject to these caveats, the data suggest that the inhibition by quinidine of Na+ transport across toad bladder does not arise primarily from membrane depolarization produced by a direct blockage of the basolateral channels. It now seems more likely that the quinidine-induced elevation of intracellular Ca2+ activity directly blocks apical Na+ entry.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01871229
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