Histological study of Leydig cells in the cat from birth to sexual maturity.

Testes of 20 cats with an age ranging from 1 day to 1 year were obtained. Histological study revealed three different populations of Leydig cells. In the early postnatal period (from birth to 1 month) they were round or polyhedral with an ovoid and eccentric nucleus. From 2 to 4-5 months Leydig cells were similar to those seen in the early postnatal period, showing shrunken nuclei with condensed chromatin masses and accumulation of lipid droplets in the cytoplasm. The peritubular Leydig cells mostly contained elongated nuclei. From 5 to 6 months of age adult Leydig cells were encountered, generally polygonal in outline with large nuclei that were usually round to ovoid and displaced to one side of the cell. The cytoplasm contained lipid droplets and lipofuscin granules. The number of testosterone-containing cells decreased progressively from 1 to 4 months; from 3 to 4 months only a small number of testosterone-containing cells were present.