. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NA* AND GLUCOSE FLUXES IN HYMENOLEPIS 157 is 2 or mure, and in rabbit iluem it is unity. The coupling coefficients appear to be independent of the glucose concentration in all of these systems. In showing first order dependence on Na+ concentration with coupling co- efficients greater than unity, glucose influx in H. diminuta resembles Na+-coupled glucose influx in C. verticillatum (Pappas and Read, 1972a), and alanine influx in the pigeon erythrocyte (Wheeler and Christensen, 1967). In the latter system, Na+-coupled influxe
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NA* AND GLUCOSE FLUXES IN HYMENOLEPIS 157 is 2 or mure, and in rabbit iluem it is unity. The coupling coefficients appear to be independent of the glucose concentration in all of these systems. In showing first order dependence on Na+ concentration with coupling co- efficients greater than unity, glucose influx in H. diminuta resembles Na+-coupled glucose influx in C. verticillatum (Pappas and Read, 1972a), and alanine influx in the pigeon erythrocyte (Wheeler and Christensen, 1967). In the latter system, Na+-coupled influxes of asparagine, hydroxyproline, serine, and threonine have coupling coefficients of 2 or more, but show a first order dependence on the Na+ 10 FIGURE 10. Effect of HIM phlorizin on the 2 min influx of "C-glucose (J'I; as in Fig. 1) in Hymenolepis diminuta; S = glucose concentration, mm; influxes with phlorizin = solid circles; influxes without phlorizin — solid squares. Each point is the mean of 3 replicates, and lines were fitted by regression analysis. concentration in the suspending medium (Koser and Christensen, 1968). On the other hand, H. diminuta differs from the above mentioned systems in that the coupling coefficient is an inverse function of the Na+ concentration. Any kinetic model which will describe the coupled influx of Na+ and glucose across the brush border of H. diminuta must account for all of the properties of the H. diminuta system indicated above, particularly the first order dependence on Na+ concentration with coupling coefficients exceeding unity. Such a model must include the following: (1) The binary complex of carrier and glucose, or binary or higher complexes of carrier and Na+ (one or more Na+), are translocated to a very minor extent. (2) Binding of one Na+ to the carrier at a single specific site results in translocation of the glucose-carrier-Na+ tertiary complex. (3) If the glucose-carrier complex is translocated at
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