EXPRESSION OF THE BETA-ISOFORMS OF NA,K-ATPASE IN THE RENAL-CORTEX OFRATS

The aim of the present study was to assess the presence of beta(1)- an d beta(2)-isoforms of the P-subunit ofNa,K-ATPase in the rat renal cor tex. This has been accomplished by immunohistochemistry and Western bl otting using isoform-specific antisera. Western blot of brain extract, used as positive control, revealed the bands corresponding to beta(1) - and beta(2)-glycosylated peptides, with a molecular weight (MW) of s imilar to 50-60 that, after exhaustive treatment with N-endoglycosidas e-F, migrated to the MW corresponding to the core peptides (similar to 35). In the renal cortex, Western blot revealed the bands correspondi ng to beta(1). After deglycosylation of the samples, the bands hybridi zing with the anti-beta(1)-antibodies moved to the MW corresponding to a partially deglycosylated form and the core peptide. Bands with a MW of similar to 50-60 hybridized with anti-beta(2), although digestion with endoglycosidase failed to move the band towards a lower MW. Immun ohistochemistry revealed the presence of beta(1)- but not beta(2)-isof orm. Northern blot for total mRNA showed strong signals for beta(1) in renal cortex, the mRNA for the beta(2)-isoform being undetectable. In conclusion, only mRNA and glycopeptide of the pl-isoform seem to be p resent in renal cortex of adult control rats.