Internalization of non-permeant materials into cultured mammalian cells by vortex-stirring in the presence of a high molecular weight polyacrylic acid: direct evidence of internalization and its dependence on the cell lines.

Laser scanning confocal fluorescence microscopic analysis provided a direct evidence of the internalization of non-permeant Lucifer Yellow and a dextran of MW 4400 into leukemia L1210 cells when the cells were vortex-stirred in the presence of a high molecular weight polyacrylic acid, A-119 (MW ca. 9 x 10(6)). The morphology of A-119-treated cells was probed by scanning electron microscopic analysis using 2% glutaraldehyde for fixation. The cells immediately after vortex-stirring with A-119 showed many blebs on the cell surface, indicative of local weakening of the plasma membrane. The blebby surface returned to normal within 5 min at 37 degrees C, but not completely at 0 degree C even after 20 min. Several cultured cell lines, murine splenocytes, and Ehrlich ascites carcinoma cells were particularly susceptible to permeabilization by this method, although the efficiency varied from one type of cell to another.