Effects of gluconeogenic precursor flux alterations on glycogen resynthesis after prolonged exercise.
The importance of gluconeogenic substrates (i.e., lactate, glycerol, and alanine) in the glycogen resynthesis observed in fasting rats after exhausting submaximal exercise [R.D. Fell et al. Am. J. Physiol. 238 (Regulatory Integrative Comp. Physiol. 7): R328-R332, 1980] was examined in muscles and liver in response to pharmacological alterations of gluconeogenic precursor flux. The minor role of lactate for glycogen resynthesis after prolonged submaximal exercise was confirmed by the insignificant accumulation of lactate neither in muscles nor in plasma. When the rate of lipolysis is reduced either by beta-blockade or by nicotinic acid injection, the replenishment of muscle glycogen persisted, suggesting that glycerol released by triglycerides hydrolysis did not play an important role in glycogen resynthesis. On the other hand, when pyruvate oxidation is enhanced by dichloroacetate (DCA), thus reducing plasma levels of lactate and alanine, glycogen resynthesis was completely blocked in liver and partly in some but not all muscles. This failure in total inhibition of glycogen resynthesis associated with the significant reduction of the plasma alanine level could be attributed to the possible stimulation of gluconeogenesis from alanine by DCA (R.A. Harris and D.W. Crabb. Arch. Biochem. Biophys. 189: 364-371, 1978). The results could point out alanine as the major gluconeogenic substrate during recovery from exhaustive exercise in fasting conditions.
Favier
R J
RJ
Unité Associeé 0621, Centre National de la Recherche Scientifique, Laboratoire de Physiologie A, Lyon, France.
Koubi
H E
HE
Mayet
M H
MH
Semporé
B
B
Simi
B
B
Flandrois
R
R
D000409:Alanine / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D003999:Dichloroacetic Acid / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005943:Gluconeogenesis / Q000187:drug effects; D005990:Glycerol / Q000097:blood; D006003:Glycogen / Q000096:biosynthesis*; D007773:Lactates / Q000097:blood; D008112:Liver Glycogen / Q000096:biosynthesis; D008297:Male; D009132:Muscles / Q000378:metabolism; D009539:Nicotinic Acids / Q000494:pharmacology; D005082:Physical Exertion; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007773:Lactates; D008112:Liver Glycogen; D009539:Nicotinic Acids; D006003:Glycogen; D003999:Dichloroacetic Acid; D011433:Propranolol; D000409:Alanine; D005990:Glycerol