Status of cochlear Na,K-ATPase in the aged SHR rat and its possible role in hearing loss.

The relationship between levels of Na,K-ATPase isoforms was studied in the lateral walls of the cochlea in aged spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. Dense staining for the enzyme's alpha 1 subunit was found especially in the basal turns of the cochlea, while external sulcal cells were more intensely stained in the more apical turns in both SHR and WKY rats. In contrast, staining for beta 1 Na,K-ATPase was demonstrable in significant levels in the stria vascularis and suprastrial regions of the SHR rat, with involvement of the basilar suprastrial region pronounced in both strains of animals. Findings suggest a spatially defined, age-induced alteration in cochlear homeostasis with a possible consequent effect on sound perception.