Morphometric Study of the Testicular Interstitium of the Rat during Postnatal Development

Kim, In Shik; Yang, Hong Hyun

Abstract

The purpose of this morphometric study was to obtain quantitative information on the rat testis interstitium during postnatal development. Eight groups of male rats aged 1, 7, 14, 21, 28, 40, 60 and 90 days (n=5 rats per group) after birth were used. Tissue from perfusion-fixed testes was embedded in Epon-Araldite; and sections were subjected to morphometric measurements at the light microscopic level, using point counting method for volume densities and the Disector technique for numerical densities (the number of cells per unit volume of testis). The volume density of the interstitium represents 66% of the testicular parenchyma at day 1. This proportion progressively diminishes during development to reach a value of 8% at day 90. The absolute volume of blood vessels, macrophages, and endothelial cells increased with age. The absolute volume of lymphatic spaces, pericytes and myoid cells were greater at 90 days than at any other age. The absolute volume of fetal Leydig cells per testis was unchanged from 1 (0.07 mm3) to 14 (0.1 mm3) days, despite a decrease in the volume density. The number of mesenchymal cells, myoid cells, macrophages, endothelial cells, and pericytes per testis increased with age. The number of fetal Leydig cells per testis did not change from days 1 (0.054 million)~21 (0.070 million) although on day 21 (615 micrometer3) an average fetal Leydig cells was smaller in volume than at earlier ages (days 1 (1338 micrometer3)~14 (1296 micrometer3)). Adult Leydig cells were recognized at day 14 and their absolute volume and number per testis increased from 14 (0.5 mm3, 0.6 million) to 90 (52.83 mm3, 21.14 million) days. The average volume of a adult Leydig cell increased significantly with age and reached maximum size by 60 days (2548 micrometer3) of age where the volume is nearly three times bigger than that of at day 14 (832 micrometer3). No change in the average volume of the macrophages could be detected in this study groups. The average volume of the mesenchymal cells decreased significantly from day 1 (812 micrometer3) to day 14 (385 micrometer3) then increased until day 28 (901 micrometer3) at which the volume is maximum and declined significantly thereafter.