Physical Chemistry of Lipoids. IV. Influence of Narcotics on the Salt-binding Capacity of Lecithin

Abstract

Direct reactions between lipoids and narcotics were missed in previous studies of viscosimetry 1 and interferometry. 2 In view of the biological importance of lipoids, one must therefore assume that narcotics influence reactions of lipoids with other substances. Nervous excitation is explained by Nernst 3 by changes of ion concentrations occurring at the surface of membranes. Experimental proof of the important rôle of lipoids in artificial polarizable membranes has recently been given. 4 The importance of lipoids in narcosis 5 has been widely assumed. Nevertheless, no data are available that connect the changes of ion concentration on the cell surface with the lipoids. Former experiments 6 on the salt-binding capacity of lecithin were therefore continued, and the influence of narcotics was examined. The lecithin sols made from egg-lecithin (extra pure Merck, Germany) were either emulsions or were prepared by the method of Keeser 7 (pouring small amounts of boiling alcoholic lecithin solutions into boiling distilled water and boiling the alcohol away). In view of former observations 2 only fresh samples of lecithin sol were used.

Since higher concentrations of lecithin were to be used, conductivity measurements were made instead of the formerly used interferometric determinations. The conductivity (K) was measured in the aqueous lecithin solutions (a), in the salt solutions (b), and in an aqueous solution (c) containing lecithin and salt in the same concentrations as in a and b respectively. The difference (KD) between the calculated values (a + b) and the observed value (e) is used as a measure for the amount of ions bound or adsorbed to lecithin. A similar method has been used by Spiegel-Adolf 8 on globulins