Structural response of the hamster Sertoli cell to hypophysectomy: A correlative morphometric and endocrine study

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Abstract
Reproductively active hamsters were hypophysectomized and examined 6 or 20 days later in a combined morphometric and endocrine study of the Sertoli cell to determine 1) the morphological and endocrine effects of hypophysectomy of both short‐ and long‐term duration, 2) if regression of Sertoli cells after hypophysectomy in a seasonal breeder resembles regression due to seasonal changes, and 3) if effects of hypophysectomy in a seasonal breeder are equivalent to the effects of hypophysectomy in a nonseasonal breeder. Six days after hypophysectomy, at a period when germ cell degeneration is first noted, there was a significant decrease in testis weight, interstitial space, tubule diameter and length, volume of seminiferous tubule, and tubular lumen. There were no significant changes in Sertoli cell nuclear and cytoplasmic volume although cell surface area was decreased significantly. Most organelles exhibited no significant change in volume or surface area except for secondary lysosomes which expectedly increased in volume as the result of phagocytosis of germinal cells. Thus at an early time period when functional changes in germ cells and Leydig cells are clearly evident (Russell et al. [1992] Endocrinology), the Sertoli cell shows minimal changes. Twenty days after hypophysectomy, the cell, nuclear and cytoplasmic volumes and surface area of the Sertoli cells, and volumes and surface areas of nearly all organelles were significantly decreased from values measured in normal and in short‐term hypophysectomized hamsters. The exceptions were the total volumes of lipid which increased significantly and lysosomes which were similar to normal but significantly lower than short‐term hypophysectomized animals. The long‐term hypophysectomized hamster Sertoli cell, like that of the short‐day hamster (Sinha Hikim et al. [1989b] Endocrinology, 125:1829–1843) is structurally regressed as a whole rather than exhibiting selective decreases in cellular and subcellular components. The size of the Sertoli cell in pituitary‐intact, long‐ and short‐term hypophysectomized animals showed positive and significant correlations with the volumes and surface areas of all its cytoplasmic organelles except the volume of lipid which showed a negative, significant correlation. Comparisons of long‐term hypophysectomized hamsters (in long‐day light exposure) and short‐day exposed animals (Sinha Hikim et al. [1989b] (Endocrinology, 125:1829–1843) suggested that hypophysectomy, in general, resulted in similar, but slightly more severe regressive changes in the testis and germ cell population than those seen during seasonal regression. This was manifest in the Sertoli cell as a significantly lower cell surface area and nuclear volume although the majority of cytoplasmic organelles of the Sertoli cell were not significantly different, nor were plasma follicle stimulating hormone (FSH) and testosterone levels dissimilar. With respect to the Sertoli cell, the structural manifestations of hypophysectomy in the hamster are strikingly similar to those detected in the rat (Ghosh et al. [1992] Endocrinology) with one exception that the Sertoli cell surface area in the rat does not decrease significantly in the short term. In correlation tests of morphological parameters and hormone levels in long‐day, short‐term and long‐term hypophysectomized hamsters, several parameters were correlated with plasma FSH and testosterone levels. The content, but not the concentration (expressed per basal compartment surface area), of FSH receptors decreased in short‐term hypophysectomized animals. Compared to the Leydig cell, the Sertoli cell structure responds slowly to hypophysectomy, but, like the Leydig cell, is markedly changed in the long term.© Willey‐Liss, Inc.