The effect of thyroxine on the coenzyme A content of some tissues.

While the rBle of thyroxine in the body’s growth, development, and maintenance is important, as yet no definitive mechanism or locus of action for it has been delineated. In a recent review, Barker (1) has considered many of the enzymatic phenomena associated with different thyroidal states, and it is obvious from a consideration of the effects of this hormone that its action has wide-spread ramifications. Martius and Hess (2) and others (3, 4) have shown that thyroxine can act as an uncoupling agent. Drabkin (5) observed that tissue levels of cytochrome c were influenced by thyroxine. Much of this type of evidence implicates thyroxine with the energetics of the body. Recently coenzyme A (CoA) has been shown to be necessary in many biochemical processes (B), and it is known that a number of these CoA-dependent phenomena are influenced by thyroxine. Minx and Cohen (7) have suggested that there is a possible interrelationship between CoA and thyroxine in intestinal peristalsis. Because of the possible interrelationship between CoA and the tissue levels of thyroxine, it was considered to be worth while to investigate the influence of thyroxine on CoR levels in the tissues of the rat.