Cornford E M, Bocash W D, Oldendorf W H
J Parasitol. 1981 Feb;67(1):24-30.
The double internal standard isotope method (utilizing both a highly diffusible [H3 water] and a nondiffusible reference isotope [113m-indium bound to ethylene diamine tetra-acetic acid]) was applied in studies of C14 glucose uptake in the rodent blood fluke. Schistosomatium douthitti. Uptake of C14-L-glucose was minimal and occurred by a diffusional mechanism alone. Transintegumental uptake of the stereoisomer C14-D-glucose, corrected for passive adsorption of the solute on the external tegumental surface, occurred by a saturable, carrier-mediated mechanism. Kinetic analyses demonstrated that glucose uptake was best described by a carrier system plus a diffusional component. Estimates were derived in male worms for the half-saturation constant (Km - 1.7 +/- 1.0 mM), maximal velocity (Vmax = 10.4 +/- 1.7 nmol.min-1.mg wet wt-1) and diffusional component (Kd = 0.57 microliters.min-1.mg wet wt-1). In females, these measurements (Km = 1.8 +/- 1.4 mM; Vmax = 11.3 +/- 2.2 nmol.min-1.mg wet wt-1; and Kd = 0.60 microliters.min-1.mg wet wt-1) were similar. These parameters were compared with estimates from mammalian tissues, and differences were attributed tentatively to the greater surface area-to-volume ratio of the schistosome.
双内标同位素法（同时使用一种高扩散性的[H3水]和一种非扩散性的参考同位素[与乙二胺四乙酸结合的113m-铟]）被应用于研究啮齿类血吸虫（杜氏血吸虫）对C14葡萄糖的摄取。C14-L-葡萄糖的摄取量极少，且仅通过扩散机制发生。经校正溶质在外皮层表面的被动吸附后，立体异构体C14-D-葡萄糖的经皮层摄取是通过一种可饱和的、载体介导的机制发生的。动力学分析表明，葡萄糖摄取最好用一个载体系统加一个扩散成分来描述。得出了雄虫的半饱和常数（Km = 1.7 +/- 1.0 mM）、最大速度（Vmax = 10.4 +/- 1.7 nmol·min-1·mg湿重-1）和扩散成分（Kd = 0.57微升·min-1·mg湿重-1）的估计值。在雌虫中，这些测量值（Km = 1.8 +/- 1.4 mM；Vmax = 11.3 +/- 2.2 nmol·min-1·mg湿重-1；Kd = 0.60微升·min-1·mg湿重-1）相似。这些参数与来自哺乳动物组织的估计值进行了比较，差异初步归因于血吸虫更大的表面积与体积比。
