Quantitation of elastin production in cultured vascular smooth muscle cells by a sensitive and specific enzyme-linked immunoassay.

An enzyme-linked immunoassay (ELISA) procedure has been developed to quantitate the amount of elastin produced by cultured porcine aortic smooth muscle cells. ELISA was used to determine both titer and specificity of antisera raised in rabbits against porcine aortic alpha-elastin conjugated with key-hole limpet hemocyanin. Under optimum conditions (1: 3000 dilution of antiserum, 20 ng alpha-elastin per assay well), sensitivity averaged 60 ng/ml). Specificity was confirmed by immunoprecipitation of [125I]-tropoelastin, radial immunodiffusion, Western blotting and lack of cross-reactivity with serum proteins or collagen. Extensive cross-reactivity was found with both human alpha-elastin and porcine beta-elastin, while porcine tropoelastin was able to compete with 80% of the alpha-elastin determinants. Affinity of anti-porcine antisera for sheep alpha- elastin was significantly lower. When the ELISA was made specific for tropoelastin by coating wells with 60 ng of this antigen, a time-dependent and serum-dependent rate of production of tropoelastin was observed in the culture medium of primary and secondary cultures of smooth muscle cells. Comparison of elastin production in cultures of porcine smooth muscle cells suggests that porcine aortic elastin production varies as a function of cell density and phase of growth.