Ultrastructural changes in rat adrenocortical cells produced by a 4-aminopyrazolopyrimidine (4-APP) dosage.

The relation between adrenal cholesterol synthesis and ultrastructural changes was studied in rat adrenal glands stimulated by 4-aminopyrazolopyrimidine (4-APP). Ultrastructural observations were focused on the inner fasciculata-reticularis (Zone I) and the outer fasciculata (Zone O) of the adrenal glands. Zone I in 4-APP-treated rat adrenals had increased tubules and vesicles in the smooth endoplasmic reticulum, mitochondrial enlargement and the accumulated osmiophilic lipid droplets. In contrast, Zone O of the 4-APP-treated rat adrenals showed a decrease in osmiophilic lipid droplets and no increase in any of the elements of the smooth endoplasmic reticulum. These results are strong evidence that under 4-APP treatment cholesterol synthesis takes place in the increased smooth endoplasmic reticulum in Zone I cells. The functional status of the cells of the inner and outer zones of the adrenal cortex also is discussed.