Dose related effects of dexamethasone treatment on the ultrastructure of articular cartilage in rats.

Corticosteroid administration is known to cause degenerative changes in articular cartilage interfering with the cell metabolism of chondrocytes. The present study analyzes the ultrastructural changes in chondrocytes after systemic dexamethasone acetate treatment in relation to dosage, using a standardized morphometrical method. Five male Wistar rats of 300 g body weight in each experimental group were subjected to 3, 4 and 5 mg dexamethasone acetate by intramuscular injections of 1 mg per week. 1000 electron micrographs of single chondrocytes in the middle zone of hyaline cartilage from the knee joints were evaluated with standardized morphometry and nonparametric statistics. With increasing dexamethasone dosage the amount of rough endoplasmic reticulum and Golgi apparatus decreased. Considerably increased glycogen granula and clusters indicated a severe change in glycolytic pathways. Lysosomes duplicated in number. Degenerative changes were also manifested in lipid droplets and myeloid bodies, which, like the amount of microfilaments, exhibited a clear dosage-dependent increase under dexamethasone treatment. The ratio of dead versus living chondrocytes increased in relation to dosage up to 25% cell mortality.