Thyroid hormone deiodination in the domestic cat

D J Foster, K L Thoday, G J Beckett

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We have investigated thyroid hormone deiodination in the liver, kidney and thyroid of the domestic cat. Affinity labelling with I-125-bromoacetyl reverse T-3 (I-125-BrAc-rT(3)) demonstrated that liver and kidney, but not the thyroid, express type I iodothyronine deiodinase (IDI), results that were confirmed by measuring the activity of the IDI using I-125-rT(3) and T-4 as substrate. Feline hepatic and renal IDI metabolised rT(3) at approximately 0.2% of the rate of rat hepatic IDI under identical assay conditions. The K-m of the feline enzyme was at least 500-fold greater than that of rat IDI. However, feline and rat hepatic IDI metabolised T-4 at a similar rate and had similar K-m values (1.35 mu M and 2.25 mu M, respectively). This study demonstrates that cats and rats express IDI in the liver and kidney in similar concentrations; however, the feline enzyme appears unable to utilise rT(3) as a substrate under physiological conditions.

Original languageEnglish
Pages (from-to)119-126
Number of pages8
JournalJournal of molecular endocrinology
Issue number1
Publication statusPublished - Feb 2000


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