title: Differential regulation of the degradation of myofibrillar and total proteins in skeletal muscle of rats: effects of streptozotocin-induced diabetes, dietary protein and starvation.
abstract: In order to examine the effects of streptozotocin-induced diabetes, dietary protein, and starvation on protein degradation in skeletal muscle of perfused rat hindquarters, rates of myofibrillar and total protein degradation were estimated from the release of 3-methylhistidine (N tau-methylhistidine, 3-MH) and tyrosine, respectively. In rats fed a 20% protein diet (controls), the fractional degradation rate of myofibrillar protein was approximately 56% of the total muscle protein. In streptozotocin-induced diabetic rats, 3-MH release by perfused muscle increased significantly on d 1 of treatment and sustained a high level thereafter. By contrast, tyrosine release did not change. Feeding a 50% protein diet for 1 wk altered neither 3-MH nor tyrosine release. Protein-free feeding, though, suppressed tyrosine release to 49% of controls, but did not affect 3-MH release. Starvation for 3 d did not affect tyrosine release, but did increase 3-MH release to 203% of controls. These results indicate that in diabetic and starved rats myofibrillar protein is preferentially degraded, while in protein-deficient rats, non-myofibrillar protein degradation is selectively suppressed. From these observations, we conclude that the degradation of myofibrillar and non-myofibrillar proteins in skeletal muscle can be differentially regulated.
authors.affiliation: Department of Agricultural Chemistry, University of Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kadowaki
authors.forename: N
authors.initials: N
authors.lastname: Harada
authors.forename: S
authors.initials: S
authors.lastname: Takahashi
authors.forename: T
authors.initials: T
authors.lastname: Noguchi
authors.forename: H
authors.initials: H
authors.lastname: Naito
mesh_terms: D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000652:urine; D004044:Dietary Proteins / Q000494:pharmacology*; D006614:Hindlimb; D007328:Insulin / Q000378:metabolism; D008297:Male; D008762:Methylhistidines / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism
chemical_list: D004044:Dietary Proteins; D007328:Insulin; D008762:Methylhistidines; D009124:Muscle Proteins; D014443:Tyrosine; C028118:3-methylhistidine