Proliferative activity in the rat epididymis during postnatal development.

The proliferative activity of the rat epididymis during postnatal development was investigated with the use of autoradiography. Animals at 14, 21, 28, 35 and 56 days of age were sacrificed 2 hours following the administration of 3H-thymidine. Cell types that showed a significant labeling index were columnar cells in 14- and 21-day-old animals; principal and basal cells in 28, 35, and 56 day old rats. During this period of development, the pattern of cellular activity in the initial segment differed from the middle and terminal segments in having a peak of activity on day 28. The middle and terminal segments had similar proliferative patterns. In two additional experiments, 10- and 21-day-old rats were given 3H-thymidine and killed 1 week later on day 16 and 28. Labeled narrow cells were present in day 16 animals, whereas labeled narrow, principal, and basal cells were found in day 28 rats. It was concluded that columnar cells are the precursor to narrow, principal and basal cells.