Responsiveness of α₁, and β₁ Cochlear Na, K-ATPase Isoforms to Thyroid Hormone

Abstract

The effects of thyroid hormone on Na, K-ATPase subunit isoforms under euthyroid (EUTH), hypothyroid (HYPO) and hyperthyroid (HYPER) states were investigated via immunocytochemistry and the use of polyclonal antibodies specific to each isoform (α₁ α₂, α₃ and β₁, β₂). in HYPO animals, there was a distinct decrease in Na, K-ATPase α₁, isoform immunoreactivity in the stria vascularis (SV), spiral ganglion (SG) cells, spiral limbus (SLi) and cochlear nerve (CN) as compared with that in EUTH animals by the 17th day of the experiment. Immunostaining of the α₁, isoform increased in HYPER animals as compared with that in HYPO animals, and reached a level comparable to that in EUTH animals after 2 days of triiodothyronine (T3) treatment. Levels of α₂ α₃ and β₂ isoforms did not appear to be affected by T₃ administration. by the 19th day of a low I₂ diet, the immunoreactive intensity of the β₁, isoform was reduced in cochlear tissues of HYPO animals as compared with that in EUTH animals. the immunoreactivity of the β₁, isoform increased after treatment with T, for 4 days and was comparable with levels in EUTH animals. These data indicate that α₁, and β₁, isoforms within specific cochlear regions of the adult rat are responsive to thyroid hormone.

Key Words:

• T₃
• sodium pump
• immunocytochemistry
• inner ear