Ionic transport through model membranes. I. Effects of accelerators of carcinogenesis.
Abstract 1. 1. Egg phosphatidyl choline adsorbed at an hydrocarbon-water interface was used as a physical model of a membrane-cytoplasm interface. The rate of transport of an anionic dyestuff could be measured across the interface from the aqueous to the organic phase under conditions of emulsification. The process simulates carrier transport in that the lecithin is an essential requirement, forming a tightly bound complex with the dye that becomes solubilized in the phospholipid micelles in the bulk organic phase. 2. 2. The standard organic phase was then modified by inclusion of n- alkanes from C 7 to C 24 . Most of the alkanes that have biological activity as accelerators of carcinogenesis, C 10 -C 20 , produced a significant reduction of the rate of transport of the dyestuff into the organic phase. 3. 3. Correlation was inferred between these observations and those of investigators of intracellular ionic transport in epithelial tissue cultures, who found a marked reduction of transport rates in certain malignant epithelia in contrast to the corresponding normal tissues. A membrane-mediated mechanism of control of initiated neoplastic cells is suggested. The hypothetical control depends upon a specific surface charge distribution at the lipoprotein-cytoplasm interface that is altered by the absorption of C 10 -C 20 n- alkanes .