Ultrastructure of the adrenocortical homologue in dexamethasone-treated eels.

The ultrastructural modifications of the adrenocortical homologue (AH) in the North American eel (Anguilla rostrata) were studied following a 10 day treatment with dexamethasone (20 mg/day). The principal changes were: disorganization of smooth endoplasmic reticlum, regression and fragmentation of the Golgi apparatus, and a lowering of matrix density in the mitochondria. Steroid treatment also induced the appearance of numerous cytoplasmic inclusions: (a) lamellated bodies with electron-lucent cores; (b) membranous whorls isolating cytoplasmic regions containing smooth endoplasmic reticulum and mitochondria and (c) complex aggregates showing whorls of membranes, residues of cytoplasmic organelles, and dense matrix. The non-accumulation of lipid droplets in repressed AH cells was noteworthy. These subcellular changes indicate endogenous cellular autophagy in the AH as a result of steroid-induced suppression of ACTH production by the pituitary.