Effects of glycerol feeding before and after exhausting exercise in rats.
Rats were fed either 1 g of glycerol or 1 g of glucose following exercise to exhaustion. Glucose feeding resulted in a rapid increase in blood glucose, with attainment of peak hyperglycemia within 1 h and of peak muscle glycogen in about 2 h. Feeding 1 g of glycerol resulted in marked elevation of glycerol concentration in blood, liver, and muscle; the highest values, measured 1 h after glycerol feeding, ranged from 29 to 42 mumol/g tissue. Blood glucose and muscle glycogen increased slowly in the glycerol-fed rats and peaked much later than after glucose feeding. In perfused rat hindlimb muscles, negligible amounts of [14C]glycerol were incorporated into glycogen. These findings suggest that muscle is not able to utilize glycerol to a significant extent and that glucose derived from glycerol was the major substrate for muscle glycogen synthesis. Animals fed glycerol before a run to exhaustion were able to exercise significantly longer than control rats (153 +/- 11 min vs. 116 +/- 6 min). The glycerol-fed rats depleted their muscle and liver glycogen stores less rapidly than the controls and were protected against development of hypoglycemia during the exercise.
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005934:Glucagon / Q000097:blood; D005947:Glucose / Q000494:pharmacology; D005990:Glycerol / Q000032:analysis / Q000494:pharmacology*; D006003:Glycogen / Q000032:analysis; D007328:Insulin / Q000097:blood; D007773:Lactates / Q000032:analysis; D008099:Liver / Q000032:analysis; D008112:Liver Glycogen / Q000032:analysis; D008297:Male; D009132:Muscles / Q000032:analysis; D005082:Physical Exertion / Q000187:drug effects*; D051381:Rats; D013997:Time Factors
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D007773:Lactates; D008112:Liver Glycogen; D006003:Glycogen; D005934:Glucagon; D005947:Glucose; D005990:Glycerol