EFFECTS OF VARIOUS ANALOGUES OF THYROXINE ON OXYGEN UPTAKE OF CARDIAC MUSCLE FROM CHICKS1

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Abstract
The response in oxygen uptake of surviving ventricular myocardium to thyroxine, 3:5:3[image]-triiodothyronine, 3:5-diiodothyronine and 3-monoiodothyronine and their acetic and propionic acid derivatives was studied in cockerels pre-treated with thiouracil. Thiouracil lowered the oxygen uptake from the normal control level of 6.0 [mu]l./hr./ mg. dry tissue to 4.0 [mu]l. Thyroxine gave a greater increase above the normal controls than any of the other compounds at all dosage levels 12 hours following intraperitoneal injection; at the higher dosage levels, triiodothyronine was the next most potent compound. The remaining compounds, in general, did not increase oxygen uptake above the normal control level except at the highest dose. The response to thyroxine reached a maximum at 9-12 hours and subsided by 36 hours; that to triiodothyronine at 12-15 hours and 18 hours respectively.