Liver has long been known to be a major site of carbohydrate formation from lactate (Cori & Cori, 1929), but in the past it has not proved possible to reproduce the synthesis satisfactorily in isolated tissue in vitro. It is true that liver slices suspended in a saline medium synthesize some carbohydrate (Takane, 1926; Buchanan, Hastings & Nesbett, 1942, 1949), but for reasons that are still obscure the rate of carbohydrate synthesis in slices is very much lower than the rate in vivo. There are no records of experiments in which the synthesis occurred in disrupted liver cells. Since cell-free material is a prerequisite for the detailed investigation of the process, efforts were made to obtain a cell-free liver preparation capable of synthesizing carbohydrate at high rates. A pigeon-liver homogenate is described below which readily forms carbohydrate from L-lactate. EXPERIMENTAL Analytical method8. Glucose and the sum of glycogen and glucose were determined enzymically by the glucoseoxidase method (see Krebs, Bennett, de Gasquet, Gascoyne & Yoshida, 1963). 'Bound' glycogen, i.e. glycogen insoluble in aqueous HC104, was determined by washing the centrifuged and well-drained sediment from the HC104 treatment twice with 2% (w/v) HC104 solution. The washed precipitate was dissolved in 1 ml. of 30% (w/v) KOH and heated in a boiling-water bath for 20 min. The glycogen was isolated according to the method of Good, Kramer & Somogyi (1933) and determined as described by Krebs et al. (1963).
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