Ultrastructural alterations in rats adrenal cortical cells produced by 4-aminopyrazolopyrimidine and ACTH administration.

The correlation between adrenal cortical steroid metabolism and ultrastructural alterations was studied in rat adrenal glands stimulated by 4-aminopyrazolopyrimidine (4-APP) and ACTH. Ultrastructural alterations were focused on the outer fasciculata (Outer zone) and inner fasciculata-reticularis (Inner zone) of the rat adrenal cortical cells. In 4-APP administered rats, the most striking ultrastructural alteration was noted in the characteristic tubular profiles of smooth endoplasmic reticulum, mainly of the Inner zone. In ACTH administered rats, proliferation of fine tubulo-vesicular profiles of smooth endoplasmic reticulum was frequently seen in intermitochondrial space in both the Outer and the Inner zones. On the other hand, by 4-APP plus ACTH administration, the most striking ultrastructural changes were detected in mitochondria, mainly of the Inner zone. These mitochondria had a highly electron dense matrix and protrusions or blebs of mitochondrial outer membrane were frequently observed. In contrast, no remarkable changes were detected in the Outer zone of the cortex, except a slight enlargement of the mitochondria. On the bases of our findings, it is strongly suggested that the Inner zone of the cortex after 4-APP plus ACTH administration, at least in part, probably corresponds to highly activated steroid synthesis and it is further, speculated that steroidogenesis in the adrenal cortical cells after 4-APP administration is partially impaired in mitochondrial 11 beta-hydroxylase system.