title: The use of tritiated water to measure absolute rates of hepatic glycogen synthesis.
abstract: Glucogen synthesis in rat liver in vivo was measured by the incorporation of 3H from 3H2O into glycogen. In meal-fed rats incorporation and the incorporation of 3H into glycogen was linear up to 100 min. Before feeding glycogen concentration and the incorporation of 3H were both low; and both rose on feeding to give maximal values after 2-3h. The glycogen concentration was maintained for a further 5h but the incorporation of 3H rapidly declined to pre-feeding values. This shows that glycogen turnover was low in the post-prandial rat. Streptozotocin diabetes decreased the rise in glycogen concentration on feeding and had a similar effect on 3H2O incorporation. Both effects were reversed by insulin administration. The number of 3H atoms incorporated per glycogen glucose moiety formed in biosynthetic experiments (2.84 +/- 0.47) was relatively constant and allowed absolute biosynthetic rates to be calculated. Degradation of glucose from glycogen labelled by 3H2O showed that most of the 3H was located at C-2 and C-5. The incorporation would arise by rapid equilibration of hexose phosphates through phosphoglucose isomerase, transaldolase and triose phosphate isomerase.
mesh_terms: D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000096:biosynthesis; D007700:Kinetics; D008112:Liver Glycogen / Q000096:biosynthesis*; D008297:Male; D009132:Muscles / Q000378:metabolism; D051381:Rats; D014316:Tritium; D014867:Water
chemical_list: D005227:Fatty Acids; D008112:Liver Glycogen; D014867:Water; D014316:Tritium; D006003:Glycogen; D005947:Glucose