Coexistence of Fast and Slow Myosin Isozymes in Human External Urethral Sphincter. A Preliminary Report

Human external urethral sphincter muscle was isolated for biochemical research. Myosin samples were prepared and pyrophosphate gel electrophoresis and two-dimensional electrophoresis were performed. Assignment in pyrophosphate gel of myosin isozymes of human external urethral sphincter was carried out by making comparisons with those from human rectus abdominis muscle. Myosin light chains in human external urethral sphincter were identified using two-dimensional electrophoresis. Human external urethral sphincter, similar to other voluntary muscles, is composed of fast and slow twitch muscle fibers, since fast and slow myosin components were shown in both pyrophosphate gel and two-dimensional electrophoretograms.