[Biochemical analysis of the external urethral sphincter of female rabbits].

The proportion of fast and slow myosin molecules in external urethral sphincter (EUS) was studied. The contents of fast and slow myosin light chains in EUS from 6 female rabbits (Japanese White, 6-month-old) were estimated using two-dimensional electrophoresis. The percentages of fast and slow myosin molecules were 54.5 +/- 14.9 and 46.0 +/- 14.9, respectively. It was thus shown that female rabbits EUS is composed of both fast and slow muscle fibers. The ratio of fast to slow myosins in female EUS was different from that in male EUS (fast myosin 90%). These results implicate that female and male EUS would be functionally distinct.