Insulin-stimulated glycogen synthesis and glycogen synthase activation after electrical stimulation of epitrochlearis muscles with different initial glycogen contents.
Glycogen synthesis increases after muscle contraction and during insulin stimulation, and insulin-stimulated glycogen synthesis is enhanced after contraction. We hypothesized that the initial glycogen content influences the magnitude of additive effect of contraction on insulin-stimulated glycogen synthesis. Contraction and insulin had full additive effect on rate of glycogen synthesis measured after contraction in muscles with normal and high glycogen content. In muscles with low glycogen, contraction increased insulin-stimulated glycogen synthesis nearly as much as in muscles with normal glycogen, but not to the sum of the two stimuli studied separately; still glycogen synthesis was generally highest in muscles with low glycogen. Glycogen synthase fractional activity inversely correlated with glycogen content and contraction increased glycogen synthase fractional activity. Contraction and insulin additively increased glycogen synthase fractional activity at all glycogen contents. In conclusion, after contraction insulin-stimulated glycogen synthesis was increased by rather similar magnitude at all glycogen contents in concert with increased glycogen synthase activation.
Lai
Yu-Chiang
YC
Department of Physical Performance, Norwegian School of Sport Sciences, PO Box 4014 Ullevål Stadion, N-0806 Oslo, Norway.
Stuenaes
Jorid T
JT
Kuo
Chia-Hua
CH
Jensen
Jørgen
J
D000818:Animals; D004558:Electric Stimulation; D004789:Enzyme Activation / Q000187:drug effects; D006003:Glycogen / Q000096:biosynthesis* / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D007328:Insulin; D006003:Glycogen; D006006:Glycogen Synthase