Relative insensitivity of avian skeletal muscle glycogen to nutritive status

Previous studies in avian species have reported time-dependent losses in mu scle glycogen with prolonged feed withdrawal (FW). However, cervical disloc ation was used to collect tissues, a method that results in significant inv oluntary muscle convulsions. In this study, cervical dislocation alone was found to reduce muscle glycogen by 23%, therefore, barbiturate overdose was used to collect tissue samples before and after FW, at the end of refeedin g, and from continuously fed controls at each interval. Additionally, plasm a samples from 6-wk-old male chickens were taken at the initiation and end of a 24-hr feed withdrawal, and at various times during refeeding. After 24 hr of FW, liver glycogen decreased markedly (77%; P < 0.05), whereas muscl e glycogen decreased slightly and transiently, such that it returned to and remained at control levels, even after prolonged (72 hr) FW. Plasma glucos e was decreased, whereas glucagon was elevated after a 24-hr feed withdrawa l (P < 0.05), when compared with control concentrations. Muscle glycogen le vels were not significantly increased over control levels after refeeding, but liver glycogen was increased by 380% (P < 0.05). Feed deprivation follo wed by refeeding resulted in increased circulating insulin and glucose leve ls when compared with control levels. Therefore, by using methods of tissue collection that ensure that muscle glycogen determinations are not confoun ded by artifactual degradation, these results verify that regulation of avi an muscle glycogen stores is similar to that in mammals. (C) Elsevier Scien ce Inc. 1999.