Calcified foci at the junction between adrenal cortex and medulla of rhesus monkeys

The occurrence of calcified foci at the junction of adrenal medulla and cortex in monkeys obtained from toxicity studies during a 10-year period is reported. The survey included reinvestigated adrenal samples from 274 male and 270 female rhesus monkeys and 52 male and 52 female cynomolgus monkeys. The incidence of calcified foci was 46% in male and 45% in female rhesus monkeys, and 6% in male cynomolgus monkeys, while their females did not show the lesion. In male rhesus monkeys, the mean number of foci was 4 for both glands, in females, 2 for the right and 4 for the left one. Initial stages indicated that the lesions develop possibly from focal apoptosis of medulla cells followed by a dystrophic mineralization. No correlation was observed concerning dose groups, test article, study length, testing facility, origin of monkeys, their sex, age, diet or final body weight. The foci of mineralization were dystrophic, species-specific in the rhesus monkey and possibly related to stress. The location of the foci at the cortico-medullary junction, precisely the location of the remnants of the fetal zone, may indicate their origin from this zone.