Morphometric changes in the adrenal medulla of intact and ethane dimethanesulphonate (EDS)-injected rats subjected to chronic treatment with isoproterenol or propranolol

Morphometric characteristics of adrenal medulla were analysed stereologically in adult male rats injected with a single dose of ethane dimethanesulphonate (EDS), an agent that causes atrophy of the inner adrenocortical zone, or vehicle, and subjected to isoproterenol (ISO) or propranolol (PROP) treatment over the following 15 days. Compared with dimethylsulphoxide (DMSO) vehicle-injected controls, in EDS-administered rats the volume of chromaffin cell nuclei was decreased. ISO treatment in these rats increased the volumes of chromaffin cells and their nuclei. Furthermore, in both EDS- and vehicle-injected rats ISO significantly enlarged the total volume of medullary blood vessels, suggesting a vasodilatatory effect of β-adrenoceptor stimulation. However, unexpectedly, in EDS-injected rats PROP treatment also caused an increase in the volumes of chromaffin cells and their nuclei. This finding, most likely, may be related to a non-β-adrenoceptor-related action of PROP. Collectively, the present results suggest that the response of adrenomedullary chromaffin cells to chronic ISO-induced β-adrenoceptor stimulation is dependent on the functional status of adrenal cortex, so that the stereologically detectable changes were found only in rats previously exposed to the destructive action of EDS on the adrenal gland cortical cells. Moreover, they indicate that ISO treatment exerts a reversing effect on the morphometrical changes of chromaffine cells induced by EDS administration.