Morphological and Hormonal Changes Following Vasectomy in Rats, Suggesting a Functional Role for Leydig-Cell Associated Macrophages

Summary The effects of bilateral vasectomy on hormone serum levels as well as Leydig cell and associated macrophage structure were analysed in parallel in rats 36 weeks following the operation. Serum testosterone was decreased in vasectomized rats (1.96 ± 0.11 ng/ml) compared with control animals (3.44 ± 0.22 ng/ml, p < 0.05). Vasectomy also resulted in an increase in serum luteinizing hormone (LH) to 0.299 ± 0.02 ng/ml compared to the control group (0.175 ± 0.01 ng/ml, p < 0.05). Also serum follicle-stimulating hormone (FSH) was increased following vasectomy (350.88 ± 15.5 ng/ml) compared to 132.0 ± 4.8 ng/ml in control animals (p < 0.01). Morphometric analysis of Leydig cells showed hypertrophy with a 19% increase of total cell area, p < 0.01 (cytoplasm 28%, nucleus 8% increase). On the ultrastructural level, leydig cells demonstrated massively dilated smooth endoplasmic reticulum characteristic for stimulated cells. There was also a significant hypertrophy of the Leydig cell-associated macrophages. The macrophage cell area was enlarged by 22%, p < 0.01 (cytoplasm 25%, nucleus 18%). Vasectomy also led to remarkable ultrastructural changes of macrophages with a marked dilated and extended rough endoplasmic reticulum. Macrophages were found in apposition to Leydig cells with close cellular contact zones, and they frequently formed cell extensions on Leydig cells. Our data obtained following vasectomy indicate that, by their close contacts to Leydig cells, as well as the known influence on Leydig-cell steroidogenesis, macrophages may form the basis of a local immunoendocrine regulation of the pituitary-gonadal axis.