Measurement of instant rates of protein degradation in skeletal
muscle of intact mice by the accumulation of bestatin-induced
peptides.
Botbol, Violeta, and Oscar A. Scornik.
Department of Biochemistry, Dartmouth Medical School, 7200 Vail
Building, Room 402, Hanover, NH 03755-3844, Tel. (603) 650-1630, Fax
(603) 650-1128, email oscar.scornik@dartmouth.edu
APStracts 4:0190E, 1997.
Bestatin, an aminopeptidase inhibitor, permits the degradation of
cellular proteins to di- and tripeptides, but interferes with the
further breakdown of these peptides to amino acids. We propose to
measure instant rates of protein degradation in skeletal muscles of
intact mice, by the accumulation of bestatin-induced intermediates.
Muscle protein was labeled by injection of L-(guanidino-14C)
-arginine; 3 days later, maximum accumulation of intermediates was
measured in abdominal wall muscles, 10 min after the intravenous
injection of 5 mg of bestatin. The peptides were partially purified
and hydrolyzed in 6N HCl, and the radioactivity in peptide-derived
arginine was determined, after conversion to 14CO2 by treatment with
arginase and urease. The measurement of bestatin-induced
intermediates provides a unique tool for studying acute changes in
muscle protein turnover in live mice. We observed a 62% increase in
muscle protein breakdown after a 16-h fast, reversed by refeeding for
3.5 h, and a 38% increase after 3 days of protein depletion.
Received 13 February 1997; accepted in final form 15 August 1997.
APS Manuscript Number E69-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 27 August 1997