The metabolism of orally administered 4-methyl-2-thiouracil in cockerels

Abstract

The metabolism of orally administered methylthiouracil (= MTU) was studied by chemical determinations in the excrements, the contents of the digestive tract, blood plasma, muscle tissue and the thyroids. Daily doses of 40, 50, 80, 100 and 120 mg MTU were used. From the results the following conclusions are drawn: 1. About half of the amount of MTU may be recovered from the excrements within 24 hours after the administration; 2. The excretion rate is maximal about 2–6 hours after the administration. Most of the excretion takes place within 12 hours, excretion is almost complete after 24 hours; 3. In blood plasma and muscle tissue the maximal concentrations (2–4 mg%) are reached in 2–5 hours, after which a rapid decline occurs and no or very little MTU may be found after 20–24 hours; 4. Concentrations of MTU in thyroid tissue are markedly higher than those in muscle tissue. The differences, however, are much smaller than those found by other investigators; 5. MTU is very rapidly absorbed from the gastro-intestinal tract. MTU is only excreted by way of the kidneys, no direct passage through the digestive tract into the excrements occurs; 6. No cumulation of MTU in muscle tissue takes place.

All these facts favour the opinion that MTU may very easily penetrate into and be just as readily eliminated from body tissues