Changes in the number, proliferation rates, and bcl-2 protein immunoexpression of epithelial and periductal cells from rat epididymis during postnatal development

To investigate 1) the correlation between the proliferative activity of epi didymal epithelium plus myoid cells and the increase in the number of these cells and 2) the role of the basal epithelial cells in the renewal of epid idymal epithelium, a quantitative evaluation of the proliferation of both e pithelial cells and periductal myoid cells in the different epididymal regi ons (caput corpus, and cauda) has been carried out during postnatal develop ment of the rat by immunohistochemical evaluation of BrdU-labeling indices. These data were correlated with cell numbers and counted by the optical di sector method. The presence of bcl-2 protein was immunohistochemically dete cted and evaluated. No significant differences in BrdU indices were observe d among epididymal regions in any stage studied. Cell proliferation decreas ed from the prepubertal period to adulthood in both epithelial and myoid ce lls in the three regions of the epididymis, suggesting a close relationship between epithelial and mesenchymal components. The numbers of both cell ty pes were significantly higher in the caput than in the corpus and cauda in all stages studied, suggesting functional differences between regions. A ne gative linear correlation between proliferative activity and cell numbers w as noted that might be related to regulation of the cell population size. B asal cells showed a lower proliferation rate than principal cells, but most of the immunoreactive bcl-2 protein, in pubertal and adult epididymides, w as observed in basal cells. Therefore, these cells might comprise a low-pro liferating and apoptosis-resistant population.