Renal Na+,K(+)-ATPase in Dahl salt-sensitive rats: K+ dependence, effect of cell environment and protein kinases.
Na+,K(+)-ATPase in renal epithelial cells plays an important role in the regulation of Na+ balance, extracellular volume and blood pressure. The function of renal Na+,K(+)-ATPase in Dahl salt-sensitive (DS) rats, an animal model for salt-sensitive hypertension, and Dahl salt-resistant (DR) rats has been studied. In Na+,K(+)-ATPase partially purified from renal cortex, affinities and the Hill coefficients for Na+ and K+ activation were similar in DS and DR rats. Only one component of low ouabain affinity site was found in both strains, indicating the presence of the alpha 1 isoform. Protein kinase C and cAMP-dependent protein kinase phosphorylated Na+,K(+)-ATPase alpha subunit in DS and DR rats, and the phosphorylation by protein kinase C was associated with an inhibition of enzyme activity. The kinetic parameters for K+ activation were also studied in a preparation of basolateral membranes and were found to be similar in DS and DR rats. In a preparation of cortical tubule cells, Na+,K(+)-ATPase activity was determined as ouabain-sensitive oxygen consumption (OS QO2). Maximal OS QO2, measured in Na+ loaded cells, was the same in DS and DR rats. The K0.5 for K+ was significantly lower in DS than DR rats (0.163 +/- 0.042 vs. 0.447 +/- 0.061 mM, P < 0.05), indicating that factors regulating Na+,K(+)-ATPase activity in intact cells are altered in DS rats. Kinetic parameters for Na+ activation in cells were the same in both strains. In summary, the function of renal Na+,K(+)-ATPase molecule is not altered in DS rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Nishi
A
A
Department of Paediatrics, Karolinska Institute, Stockholm, Sweden.
Bertorello
A M
AM
Aperia
A
A
D000818:Animals; D006973:Hypertension / Q000201:enzymology*; D007672:Kidney Cortex / Q000201:enzymology*; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D012965:Sodium Chloride; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium