Studies of adrenocortical structure and function in rats with a transplantable mammotropic pituitary tumor

Adrenal cortical structure and function have been studied in hyperplastic rat adrenal glands which result from the presence of a mammotropic pituitary tumor (MtT) secreting very large quantities of ACTH. Compared to normal rat adrenals, the hyperplastic adrenals when homogenized and incubated with progesterone-4¹⁴C, produced little 18-hydroxy-11-deoxycorticosterone¹ (18-OH-DOC) and corticosterone but did convert progesterone efficiently to 11-deoxycorticosterone (DOC). Mitochondria isolated from the hyperplastic adrenals also showed reduced 11β- and 18-hydroxylating activities when compared to normal rat adrenal mitochondria and this correlated well with reduced levels of cytochrome P-450 in the hyperplastic adrenal mitochondria. The reduced cytochrome P-450 levels of these mitochondria also correlated with abnormal ultrastructure observed by electron microscopy. Hyperplastic adrenal mitochondria had reduced numbers of vesicular cristae in zona fasciculata cells compared to normals. The decreased 11β-hydroxylating activity of the mitochondria from hyperplastic adrenals was reflected in greatly elevated peripheral plasma levels of DOC.