Leydig cell differentiation in the prepubertal rabbit testis

Abstract

The pattern of Leydig cell differentiation in the postnatal rabbit was studied. The adult generation of Leydig cells appears at 5-6 weeks of age, with a sharp rise in the percentage of Leydig cells in the interstitial tissue at 6-7 weeks. There is a further steady, although less steep increase up to 9-10 weeks and a second sharp rise at 10-11 weeks to reach adult levels. Mitosis is active in the interstitial tissue between 5 and 7 weeks, then falls off sharply and is absent after 9 weeks. The increase in relative numbers of Leydig cells is therefore only partly a result of cell multiplication and primarily due to differentiation of cells in the testicular interstitium. Partially differentiated cells comprise a significant and relatively constant proportion of the interstitial cell population throughout the postnatal period, as occurs during fetal Leydig cell development, indicating similarity in the pattern of differentiation of the two Leydig cell generations. However, the differentiation process occurs over several weeks postnatally, as opposed to only a few days in the fetus.