Altered expression of G proteins in thyroid gland adenomas obtained from hyperthyroid cats

Objective - To determine whether expression of G proteins (G(i) and G(s)) i s altered in thyroid gland adenomas obtained from hyperthyroid cats. Sample Population-Adenomatous thyroid glands obtained from 8 hyperthyroid c ats and thyroid glands obtained from 4 age-matched euthyroid cats. Procedure-Expression of G(i) and G(s) was quantified in enriched membrane p reparations of thyroid gland tissue, using immunoblotting with G(i) and G(s ) antibodies and toxin-catalyzed ADP-ribosylation. Results - Expression of G(i) was significantly reduced in thyroid gland ade nomas from hyperthyroid cats, compared with normal thyroid gland tissue fro m euthyroid cats. Expression of G(s) was similar between the 2 groups. Conclusions and Clinical Relevance - A decrease in expression of G(i) in ad enomatous thyroid glands of cats may reduce the negative inhibition of the cAMP cascade in thyroid cells, leading to autonomous growth and hypersecret ion of thyroxine. Understanding the molecular mechanisms for hyperthyroidis m in cats may lead to better treatment or, ultimately prevention of the dis ease.