[Structural and functional characteristics of the sarcoplasmic reticulum membranes of the skeletal muscles in thyrotoxicosis].

A rate of CA2+ accumulation and efficiency of Ca2+-pump were decreased in the fractions of skeletal muscle sarcoplasmic reticulum isolated from rabbits with thyrotoxicosis. Temperature of phase transition in membranes of sarcoplasmic reticulum was changed by 4-5 degrees towards low temperatures. Under conditions of thyrotoxicosis fatty acid composition of total lipids from the sarcoplasmic reticulum fractions was altered as follows: amount of palmitic acid was increased 1.4-fold but oleic and arachidonic acids were decreased 21.8% and 40.5%, respectively. Modification of Ca2+-transport properties in sarcoplasmic reticulum caused by long-term administration of thyroid hormones into animals appears to alter the membrane protein-lipid composition.