Formation of Diiodotyrosine (DIT) by Ether-Link Cleavage of T4 in Rat Liver Homogenate as Measured by DIT Radioimmunoassay
Recent studies clearly demonstrate that extrathyroidal formation of diiodotyrosine (DIT) by cleavage of the ether bridge of T4 is an existing pathway of T4 metabolism. Tracer techniques demonstrated DIT production by this pathway in vitro in phagocytosing human leukocytes (1) and both in vitro and in vivo in the rat (1,2). Further evidence was provided by very recent in vivo studies on the turnover of DIT and T4 in thyroidectomized T4-substituted rats (3). The present paper describes studies on this metabolic process in rat liver homogenate using a sensitive radioimmunoassay for direct measurement of T4-derived DIT. Initial preliminary results have been reported elsewhere (4).
KeywordsDiphenyl Ether Ether Bridge Sensitive Radioimmunoassay Chelate Agent EDTA Unlabeled Substrate
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