The effect of phloridzin on carbohydrate metabolism in vitro

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Abstract
Carbohydrate synthesis in liver slices is partly suppressed by NaF and iodoacetate but is apparently increased by phloridzin through inhibition of carbohydrate disappearance in the early stage of incubation. This disappearance is due to oxidation rather than to fermentation of carbohydrate and is unaffected by insulin; phloridzin thus inhibits carbohydrate oxidation in vitro. This view is supported by a regularly occurring inhibition of O2 consumption by phloridzin at the same period of in-cubation at which in its absence carbohydrate oxidation mainly takes place. Further evidence is an R.Q. approaching unity in the absence and 0.58 in the presence of phloridzin. Phloretin, unlike phloridzin, partly inhibits both O2 uptake and carbohydrate synthesis in liver slices in conc. higher than 0.001 M. When glucose is also added, phloretin shows an effect similar to that of phloridzin on carbohydrate synthesis. The phloridzin effect is thus probably due to the complete glucoside rather than to its constituents. The above phenomenon and the fact that the carbohydrate level of liver tissue remains unchanged when incubated with phloridzin under anaerobic conditions dispose of the idea of a possible hydrolysis of the glucoside during the period of incubation, which otherwise could have vitiated the ob-servations.