ヒト外尿道括約筋の組織化学的検討

Abstract

Human external urethral sphincters (n = 13) were studied histochemically, using ATP-ase staining. The proportions of constituent muscle fiber types (slow twitch type 1 fibers: 35.6-97.7%, mean 65.7%, SD 16.6) were different among the individuals. There were no significant relationships between the percentage of type 1 fibers and the sex or the age. As for the mean muscle fiber diameter of 13 cases, the sizes of type 2 fibers (19.2-42.4 um, mean 27.8 um) were significantly (p less than 0.05, t-test) larger than those of type 1 fibers (15.7-30.3 um, mean 22.3 um). In analyses of individual cases, 10 male cases had significantly larger type 2 fibers than type 1. Two of 3 female cases had no significant difference in diameter between the two fiber types and the remaining 1 female case, in contrast with male cases, had significantly larger type 1 fibers than type 2. There was no significant relationship between the proportions and the diameters of constituent muscle fiber types. Our study thus showed extreme interindividual variation and implicated the presence of sexual difference in human external urethral sphincter muscle.