ISSN:
1432-1424
Keywords:
furosemide
;
HeLa cells
;
Na+
;
K+
;
Cl+−
;
cotransport
;
potassium
;
rubidium influx
;
sodium
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The effects of intracellular K+ and Na+ (K+ c, Na+ c) on the Na+,K+,Cl+− cotransport pathway of HeLa cells were studied by measuring ouabain-insensitive, furosemide-sensitive Rb+ influx (JRb) at various intracellular concentrations of K+ and Na+ ([K+]c, [Na+]c). When [K+]c was increased and [Na+]c was decreased, keeping the sums of their concentrations almost constant, JRb as a function of the extracellular Rb+ or Na+ concentration ([Rb+]e, [Na+]e) was stimulated. However, the apparent K 0.5 for Rb+ e or Na+ e remained unchanged and the ratio of the apparent K +0.5 for K+ c and the apparent K i for Na+ c was larger than 1. When JRb was increased by hypertonicity by addition of 200 mM mannitol, the apparent maximum JRb increased without change in the apparent K 0.5 for Rb+ e. These results show that K+ c stimulates and Na+ c inhibits JRb, without change in the affinities of the pathway for Rb+ e and Na+ e. The affinity for K+ c is slightly lower than that for Na+ c. Hypertonicity enhances JRb without any change in the affinity for Rb+ e. We derived a kinetic equation for JRb with respect to K+ c and Na+ c and proposed a general and a special model of the pathway. The special model suggests that, in HeLa cells, JRb takes place when Rb+ e binds to the external K+ binding site of the pathway after the binding of K+ c to the internal regulatory site.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00239001
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