Sexual and Regional Differences in Myosin Heavy Chain Expression in the Rat External Urethral Sphincter

This study used triple immunofluorescence labeling to visualize one slow (type 1) and two fast (types 2A and 2B) myosin isoforms in rat external urethral sphincters from both sexes. Type 2A fibers predominated throughout the sphincter and type 2B fibers were restricted to the proximal one‐third of the external urethral sphincter in the female rats. Type 1 fibers were present adluminally and were concentrated in the proximal and distal segments of the sphincter. While most of the male external urethral sphincter comprised type 2B fibers, type 2A fibers intermingled among these fibers in the proximal one‐third of the sphincter, and a few type 1 fibers were present that were restricted to the adluminal region of the proximal segment. The fiber‐type compositions and their areal densities changed in both sexes after gonadectomy. The areal density of the type 1 fibers increased significantly in the ovariectomized females, especially in the distal segment. In the orchidectomized males, the areal densities of the type 1 and type 2A fibers increased significantly, but that of the type 2B fibers decreased. These results indicate that myosin heavy chain expression in the rat external urethral sphincter is sexually dimorphic and shows regional differences. This article is protected by copyright. All rights reserved.
Source: The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology - Category: Molecular Biology Authors: Tags: Full Length Article Source Type: research