Comparison of the fates of ingested leucine and ingested 2-ketoisocaproate in rats.
We previously reported that the ratio, R, of 14C to 3H in the leucine of whole body protein, measured 6 h after ingestion of [3H]leucine and [1-14C]2-ketoisocaproate is equal to ratio of the dose of leucine to the dose of 2-ketoisocaproate (KIC) (on a leucine-free diet) required to achieve the same rate of growth. To determine whether R is dependent on the interval between injection and sampling, R was measured at intervals in purified whole body protein after oral injection of these isotopes in groups of rats; it was constant from 1 h onward for 1 wk, averaging 0.64 +/- 0.01 (means +/- SEM). Thus, the extent of incorporation into the leucine of whole body protein of ingested KIC remains close to 64% of the incorporation of ingested leucine administered as such simultaneously, from 1 h onward for at least 1 wk.
Imura
K
K
Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Walser
M
M
D000818:Animals; D002250:Carbon Radioisotopes; D005753:Gastric Mucosa / Q000378:metabolism*; D007408:Intestinal Absorption; D007651:Keto Acids / Q000378:metabolism / Q000493:pharmacokinetics*; D007930:Leucine / Q000378:metabolism / Q000493:pharmacokinetics*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium
D002250:Carbon Radioisotopes; D007651:Keto Acids; D014316:Tritium; C013082:alpha-ketoisocaproic acid; D007930:Leucine