LIPOLYTIC DISORGANIZATION OF THE MUSCLE CELL MEMBRANE AND THE MOVEMENTS OF MEMBRANE Na⁺ AND Ca⁺⁺

抄録

Using isolated frog sartorius muscles, participation of Na and Ca ions in the maintenance of the architectural resting state of the membrane was investigated by observing the change in ionic linkage between these ions and membrane lipid which is a master substance of the membrane. The dissociation of radioisotopic Na and Ca from the membrane and the change in Na and K contents were examined when lipase, lecithinase and heparin were applied externally.1. Lipase was less effective in producing the change in concentrations of muscle Na and K, as compared with other enzymes. It was presumed that the substrate which was influenced by lecithinase was different, as far as the experiments on ²² Na efflux and ion contents were concerned, from that which was affected by lipase. Recovery of the muscle treated lipolytically was incomplete, when viewed from the restoration of ion contents or mechanical activity.2. ²² Na efflux was increased continuously by lecithinase at lower concentrations and transiently by lipase at higher concentrations. The sites to which ouabain demonstrates its specific activity lose their responsive ability by lipase. It is supposed that the structure of active Na transport is principally built up by lipids which are hydrolyzed strongly by lipase and weakly by lecithinase.3. Release or exchange of membrane Ca was increased by lipolysis but was stabilized by proteolysis. The pattern of ⁴⁵Ca efflux in K free Ringer and that by lipolytic enzymes could superpose on each other as an algebraic sum, while ⁴⁵Ca efflux in Ca free Ringer containing the enzyme was increased in “either-or” manner that when one condition of them demonstrated its own effect the other could not show its specific effect. There is a part of membrane Ca which contributes to aggregate lipid components, and the sites that these Ca ions are playing a role in combining lipids are affected more strongly by lipase than by lecithinase.