The aim of the present study was to assess the presence of beta1- and beta2-isoforms of the beta-subunit of Na,K-ATPase in the rat renal cortex. This has been accomplished by immunohistochemistry and Western blotting using isoform-specific antisera. Western blot of brain extract, used as positive control, revealed the bands corresponding to beta1- and beta2-glycosylated peptides, with a molecular weight (MW) of approximately 50-60 that, after exhaustive treatment with N-endoglycosidase-F, migrated to the MW corresponding to the core peptides (approximately 35). In the renal cortex, Western blot revealed the bands corresponding to beta1. After deglycosylation of the samples, the bands hybridizing with the anti-beta1-antibodies moved to the MW corresponding to a partially deglycosylated form and the core peptide. Bands with a MW of approximately 50-60 hybridized with anti-beta2, although digestion with endoglycosidase failed to move the band towards a lower MW. Immunohistochemistry revealed the presence of beta1- but not beta2-isoform. Northern blot for total mRNA showed strong signals for beta1 in renal cortex, the mRNA for the beta2-isoform being undetectable. In conclusion, only mRNA and glycopeptide of the beta1-isoform seem to be present in renal cortex of adult control rats.