Leucine catabolism and incorporation into tissue proteins in thyroparathyroidectomized rats.
We investigated parameters of leucine metabolism in thyroparathyroidectomized (TPX) and pair-fed control rats using a technique of continuous infusion of [l-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 mumole/hr/100 g, mean +/- SEM, six rats). There was no significant difference between rates of alpha-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 (alpha-ketoisocaproate) in plasma, liver, and muscle. We conclude that hypothyroidism does not alter catabolism of leucine but reduces its incorporation into muscle protein.
Vazquez
J A
JA
Department of Medicine, Montefiore Hospital, Pittsburgh, PA 15213.
Paul
H S
HS
Adibi
S A
SA
D000818:Animals; D001835:Body Weight; D007651:Keto Acids / Q000097:blood / Q000378:metabolism; D007930:Leucine / Q000097:blood / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D010280:Parathyroid Glands / Q000502:physiology*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000502:physiology*; D013965:Thyroidectomy
D007651:Keto Acids; D009124:Muscle Proteins; D011506:Proteins; C013082:alpha-ketoisocaproic acid; D007930:Leucine