Synthesis of Apolipoprotein A-I in the Skeletal Muscle of the Developing Chick

Abstract

In 1982 Blue et al. reported for the first time that in rooster, apolipoprotein A-I (apo A-I) is synthesized not only by liver and intestine, as in mammals, but also by several peripheral tissues, including the heart and the skeletal muscle (1). They also found that apo A-I produced by peripheral tissues has charge properties and isoform composition super-imposable to those of apo A-I synthesized by liver and intestine (1). Since then, other reports have confirmed Blue’s observation with regard to the synthesis of apo A-I in the skeletal muscle and have pointed out that a “ burst ” in apo A-I synthesis in skeletal muscle occurs around the time of hatching. This increased synthesis is associated with a parallel change of the level of translatable apo A-I mRNA (2,3). Apo A-I mRNA level and apo A-I synthesis decrease rapidly after the first week of post-natal life (2, 3). The physiological significance of elevated apo A-I production by the skeletal muscle of the newborn chick is still poorly understood. It has been suggested that the synthesis of apo A-I in skeletal muscle may be important for: a) the local traffic and distribution of lipids among the muscle cells and the cellular organelles of a rapidly growing tissue; b) the removal of lipids accumulated in the skeletal muscle during the prenatal life; c) the differentiation of myoblasts into mature muscle fibers.