Plasma skeletal muscle myosin phenotypes identified by immunoblotting are associated with pulmonary embolism occurrence in young adults

Purified skeletal muscle myosin (SkM) binds factor Xa and is procoagulant. The molecular forms of SkM in human plasma have not been characterized. Method: Human plasma SkM heavy chain (HC) isoforms of different molecular weights were detected by a newly developed immunoblotting protocol. In this pilot study, the distribution of SkM HC antigen isoforms in plasmas of healthy subjects and young adult patients with venous thrombosis was analyzed.

Three SkM HC antigen phenotypes were identified in human plasma by immunoblotting, and Type II phenotype was correlated with the occurrence of isolated pulmonary embolisms in younger patients.

Multiple SkM HC antigen bands were detected in human plasmas, corresponding to full-length SkM HC, heavy meromyosin, or the S1 fragment. Plasma immunoblots of healthy subjects displayed three major phenotypes: Type I with two primary bands for full-length SkM and heavy meromyosin, and two lesser bands including S1 fragment (54%); Type II with bands primarily for full-length SkM HC (34%); and Type III with only a band for the S1 fragment (12%). Plasma SkM HC antigen Type II phenotype was associated with an increased occurrence of isolated pulmonary embolism in younger patients, respectively (≤50 years old). Conclusions: Three SkM HC antigen phenotypes were identified in human plasma by immunoblotting, and Type II phenotype was correlated with the occurrence of isolated pulmonary embolisms in younger patients.