[Calcium transport in proteoliposomes incorporating membranes of skeletal muscle T-system]

Using the radioisotope method, the Ca2+ transport through proteoliposomes was investigated. The proteoliposomes originating from total brain lipids and skeletal muscle T-system membranes of the rabbit were shown to possess a Ca2+ permeability which can be stimulated by 1.4-dihydroxypyridine derivatives (10(-9)-10(-7) M). Verapamil and Cd2+ (10(-5) M and 10(-3) M, respectively) inhibit the Ca2+ permeability of proteoliposomes stimulated by dihydroxypyridine derivatives. The activating effect of the latter depends on the microviscosity of the proteoliposome lipid bilayer. An addition of cholesterol to brain phospholipids at a ratio of 1:5 increases the stimulating effect of dihydroxypyridine by 50%.