[Change in transport kinetics of D-xylose in frog muscle fibers due to the specific inhibitors of sugar transport phlorhizin and phloretin].

The phloretin and phlorizin inhibition kinetics of D-xylose transport into muscle fibres of Rana temporaria has been studied. Phlorizin inhibits the entry of D-xylose competitevely and reversibly with Ki = 2.8 . 10(-4)M. Ki =9.8 . 10(-5)M has been attributed for phloretin inhibition. Phloretin inhibition was slightly reversible and depended on the state of muscle fibres. The decree of inhibition of sugar exit did not exceed that of sugar entry into the muscle fibres. The effect of phlorizin (5 . 10(-5) and 1 . 10(-4)M) and phloretin (2 . 10(-4)M) was not additive.