Abstract
Abstract
We investigated parameters of leucine metabolism in thyroparathyroidectomized (TPX) and pair-fed control rats using a technique of continuous infusion of [1-14C]leucine. The rate of leucine turnover was significantly smaller in TPX than in control rats (42.5 ± 2.6 vs 35.1 ± 1.9 μmole/hr/100 g, mean ± SEM, six rats). There was no significant difference between rates of α-decarboxylation of leucine by the two groups of rats. The protein incorporation of leucine was significantly smaller in the muscle of TPX than control rats (39 ± 5 vs 24 ± 4 pmole/mg protein, mean ± SEM, six rats) but in liver it was not significantly different. Thyroparathyroidectomy also had no significant effect on concentration of either leucine or its ketoacid (α-ketoisocaproate) in plasma, liver, and muscle. We conclude that hypothyroidism does not alter catabolism of leucine but reduces its incorporation into muscle protein.
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