MORPHOLOGICAL AND MORPHOMETRIC CHANGES IN THE ADRENAL GLAND UNDER THE INFLUENCE OF MYCOBACTERIA: AN AGE-DEPENDENT EXPERIMENTAL STUDY

Background. The adrenal gland is a central organ of the stress and immune-endocrine response, and chronic systemic inflammation induced by mycobacteria-containing Freund's adjuvant may cause marked morphofunctional remodelling of the adrenal cortex. Aim. To evaluate the age-dependent morphological and morphometric changes of the adrenal gland in outbred rats exposed to mycobacteria, covering the cortical parenchyma, microvasculature and cellular compartment. Materials and methods. Outbred white male rats aged 4 and 9 months were used; exper­imental animals received a single subcutaneous injection of Freund's adjuvant containing killed mycobacteria, and intact animals served as controls. Adrenal tissue was studied by haematoxylin–eosin and van Gieson staining, and five morphometric parameters were quantified (M ± m; p < 0.05). Results. Mycobacterial exposure produced, at both ages, a decrease in zona fasciculata thickness and in the lipid content of corticocytes, and an increase in sinusoid capillary diameter, macrophage and lymphocyte counts. In 4-month animals the changes were predominantly com­pensatory and reversible, whereas in 9-month animals a more pronounced destructive response was observed, with vacuolisation and fatty dystrophy of fasciculata cells, vascular dilation and hyperaemia. Conclusion. Mycobacteria induce a reproducible, age-modified complex of dystrophic, microcirculatory and immune-inflammatory changes in the rat adrenal cortex, with a shift from compensation at a younger age towards decompensation at an older age, confirming the model's value for studying chronic inflammation-associated adrenal injury.