THE EFFECTS OF TRIIODO- l -THYRONINE AND l -THYROXINE ON THE OXYGEN CONSUMPTION AND BODY WEIGHTS OF RATS FED ON A DIET CONTAINING 0·05% PROPYLTHIOURACIL

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  • AHA. C. L. Hsieh
    A. C. L. Hsieh
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Abstract
SUMMARY The effects of triiodo-l-thyronine (T3) and l-thyroxine (T4) on the oxygen consumption of normally fed rats and rats fed on a diet containing 0·05% propylthiouracil (PTU) have been determined over a dose range of 0·039 to 20 μg./day for T3 and 0·312 to 160 μg./day for T4. PTU increases the sensitivity of rats to T3 but decreases their sensitivity to T4. A bioassay of T3 using change in weight of PTU-fed rats after 5–7 days of daily subcutaneous injections has been performed. It is pointed out that the simplicity, sensitivity (dose range 0·05 to 0·2 μg./day) and precision (s/b ratio of about 0·13) may outbalance the disadvantage in length of time required for the assay.