Detection of caldesmon in muscle and non-muscle tissues of the chicken using polyclonal antibodies.

Polyclonal antibodies raised in rabbits against chicken gizzard caldesmon have been purified and used in immunoblotting experiments to study the distribution of this actin- and calmodulin-binding protein in diverse tissues of the chicken. Total homogenates and heat-treated homogenate supernatants derived from each tissue were subjected to sodium dodecyl sulfate-polyacrylamide gradient slab gel electrophoresis and immunoblotting using the horseradish peroxidase method. All chicken tissues examined contained caldesmon of Mr = 141,000. The amount of caldesmon found in the different tissues varied considerably and semi-quantitative comparison of stained immunoblots indicated the following relative caldesmon contents: gizzard greater than oesophagus greater than duodenum = small intestine greater than lung greater than aorta greater than heart = skeletal muscle greater than kidney = trachea greater than brain greater than liver. Each tissue revealed small amounts of lower Mr immunoreactive proteins, predominantly bands of Mr 94,000 and 70,000, which appear to be proteolytic fragments of caldesmon. Isolated caldesmon was found to be highly sensitive to proteolysis. The widespread distribution and similarity of caldesmon in different tissues of the chicken suggest its functional importance and structural conservation.