Morphometric analyses of the epididymis from normal and vasectomized rats

Abstract

To provide a structural basis for region-specific biochemical activities of rat epididymal cells and to assess the morphometric effects of vasectomy, tissue and cellular morphologic parameters for each of six histologically defined regions from the epididymis of long-term sham-operated and vasectomized rats were analyzed stereologically. In sham-operated rats, tubule diameter generally increased from region 1 to region 6 (163 microns to 338 microns) while tubular wall height decreased (35 microns to 17.5 microns) as did tubular wall volume density (0.48 to 0.12). For columnar epithelial cells, the absolute cell number/region ranged from 16.5 to 5.1 X 10(6) such that region 2 greater than region 1 greater than region 5 greater than region 4 greater than region 6 greater than region 3. Based on cell volume, the largest columnar epithelial cells were found in region 3 (2607 +/- 127 microns3). The epididymal tubule wall was made up of 91% columnar epithelial cells, 5% lymphocytes, and 4% basal cells. The relatively small tubular lumen, large wall volume, and large columnar epithelial cell number in the caput (regions 1 to 3) provide the structural basis for maximizing biochemical interactions between columnar epithelial cells and spermatozoa. In contrast, the distal cauda (region 6), with its large lumen and small tubular wall volume, is structurally optimized for the function of storage, which requires minimal columnar epithelial cell interaction with spermatozoa. In vasectomized rats, mean tissue volumes for most epididymal regions were significantly greater than in sham rats. The absolute number of lymphocytes in vasectomized rats significantly increased in several regions, thus implicating them in post-vasectomy events.