Quantitative study on the effect of an ACTH-producing pituitary tumor on the ultrastructure of the mouse adrenal gland.

The ultrastructure of the adrenal cortex was studied by quantitative stereologic techniques in LAF1 mice bearing a transplantable, ACTH-secreting pituitary tumor (AtT). The tumor stimulated a significant increase in volume and surface area of smooth endoplasmic reticulum and mitochondrial membranes in all three zones of the adrenal cortex. Concomitantly, plasma corticosterone was increased significantly in tumor-bearing animals. The AtT was an adenoma of the chromophobe type. Continuity of the nuclear membrane with the rough endoplasmic reticulum was readily observed in tumor parenchymal cells.