Effect of corticosterone administration at varying levels on leucine oxidation and whole body protein synthesis and breakdown in adrenalectomized rats.
Adrenalectomized rats were implanted with pellets containing corticosterone in proportions varying from 0% to 100%, plus cholesterol. Stable levels of plasma corticosterone resulted, varying from close to zero (I) to physiologic (II) to supraphysiologic (III). Whole body protein synthesis (S) was measured during fasting by a technique involving injection of [1-14C]-leucine, analysis of expired air for 14CO2, and measurement of urinary excretion of urea N plus ammonia N (C). Whole body breakdown (B) during fasting was calculated as the sum of S and C. C rose progressively from I to III, but fractional oxidation of 14C leucine was lowest in II. Both S and B were markedly reduced in I and maximal in II. In III, S fell but B remained high. Thus variations in glucocorticoid levels above and below physiologic exert profound effects on leucine oxidation and protein turnover, involving effects on both synthesis and breakdown.
Quan
Z Y
ZY
Department of Pharmacology and Molecular Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD 21205.
Walser
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M
D000315:Adrenalectomy; D000818:Animals; D003345:Corticosterone / Q000097:blood / Q000494:pharmacology*; D007930:Leucine / Q000378:metabolism*; D008297:Male; D009584:Nitrogen / Q000652:urine; D010084:Oxidation-Reduction / Q000187:drug effects; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D011506:Proteins; D007930:Leucine; D009584:Nitrogen; D003345:Corticosterone