RESTRICTED DIFFUSION AND EXCHANGE OF INTRACELLULAR WATER - THEORETICAL MODELING AND DIFFUSION TIME-DEPENDENCE OF H-1-NMR MEASUREMENTS ON PERFUSED GLIAL-CELLS

Intracellular diffusion properties of water in F98 glioma cells immobi lized in basement membrane gel threads, are investigated with a pulsed -field-gradient spin-echo NMR technique at diffusion times from 6 to 2 000 ms and at different temperatures. In extended model calculations t he concept of 'restricted intracellular diffusion at permeable boundar ies' is described by a combined Tanner-Karger formula. Signal componen ts in a series of ct experiments (constant diffusion time) are separat ed due to different diffusion properties (Gaussian and restricted diff usion), and physiological as well as morphological cell parameters are extracted from the experimental data. The intracellular apparent diff usion coefficients strongly depend on the diffusion time and are up to two orders of magnitude smaller than the self diffusion constant of w ater. Propagation lengths are found to be in the range of 4-7 mu m. He reby intracellular signals of compartments with a characteristic diame ter could be selected by an appropriate gradient strength. With cg exp eriments (constant gradient) a mean intracellular residence time for w ater is determined to be about 50 ms, and the intrinsic intracellular diffusion constant is estimated to 1 x 10(-3) mm(2)/s. Studying the wa ter diffusion in glial cells provides basic understanding of the intra cellular situation in brain tissue and may elucidate possible influenc es on the changes in the diffusion contrast during ischemic conditions . (C) 1998 John Wiley & Sons, Ltd.