A comparative study in twelve mammalian species of volume densities, volumes, and numerical densities of selected testis components, emphasizing those related to the sertoli cell

Abstract

Morphometric studies were performed on 12 mammalian species (degu, dog, guinea pig, hamster, human, monkey, mouse, opossum, rabbit, rat, stallion, and woodchuck) to determine volume density percentage (V v%), volume (V), and numerical density (N v) of seminiferous tubule components, especially those related to the Sertoli cell, and to make species comparisons. For most species, measurements were taken both from stages where elongate spermatids were deeply embedded within the Sertoli cell and from stages near sperm release where elongate spermatids were in shallow crypts within the Sertoli cell. Montages, prepared from electron micrographs, were used to determine V v% of Sertoli cell components in seminiferous tubules. Excluding the tubular lumen, the Sertoli cell occupied from a high of 43.1% (woodchuck) to a low of 14.0% (mouse) of the tubular epithelium. There was a strong negative correlation (r =−0.83; P<0.005) of volume occupancy of Sertoli cells with sperm production. Nuclear volume, as determined by serial reconstruction using serial thick sections, ranged from a high of 848.4 μm 3 (opossum) to a low of 273.8 μ 3 (degu). There was no correlation (r=0.02) of nuclear volume with volume occupancy (V v%) in the tubule. Sertoli cell volume was determined by point‐counting morphometry at the electron‐microscope level as the product of the nuclear size and points determined over the entire cell divided by points over the nucleus. Sertoli cell V ranged from 2,035.3 μm 3 (degu) to 7,011.6 μm 3 (opossum) and was highly correlated (r=0.85; P<0.001) with nuclear size. However, there was no significant correlation between the Sertoli cell size (V) and volume occupancy (V v%; r = 0.13) or sperm production (r = 0.21). Stereological estimates of the numerical density (N v) of Sertoli cells ranged from a high of 101.9 × 10 6 (monkey) to a low of 24.9 × 10 6 (rabbit) cells per cm 3 of testicular tissue. There was no correlation of numerical density of Sertoli cells with sperm production (r=0.002). A negative correlation was, however, observed between the numerical density of the Sertoli cells and the Sertoli cell size (r=−0.79; P<0.002). Data from the present study are compared with those previously published. This is the first study to compare Sertoli cell morphological measurements using unbiased sampling techniques. Morphometric data are provided which will serve as a basis for other morphometric studies.