Cholesterol side-chain cleavage activity and levels of high-spin cytochrome P-450in adrenal-regeneration hypertension (ARH)

Whatever steroids are involved in the pathogenesis of adrenal-regeneration hypertension (ARH), cholesterol side-chain cleavage (SCC) activity is a prerequisite for their synthesis. Both cholesterol SCC and 11β-hydroxylase activities were compared in our experiments. By combining the use of cyanoketone, a 3β-ol dehydrogenase inhibitor, with a sensitive radioimmunoassayfor pregnenolone, we were able to measure pregnenolone formed from endogenous cholesterol in adrenal mitochondrial incubations. The results from a quiescent sacrifice indicated greater SCC activity in the ARH group (0.75 nmoles prognenolone/minute/mg protein) than in controls (0.45 nmoles pregnenolone/minute/mg protein). This was related to the significantly greater (p < 0.001) amount of SCC cytochrome P-450 in the high spin state observed in adrenal mitochondria from the ARHgroup (determined by the pregnenolone-induced modified Type II spectral, change). After ether stress, both control and ARH groups had comparableamounts of high-spin SCC cytochrome P-450 and pregnenolone formation (2.5 nmoles pregnenolone/min/mg protein). llβ-Hydroxylase activity was lower in adrenal mitochondria from the ARH group (10.8 ± 0.35 nmoles corticosterone/min/mg protein) than in controls (14.0 ± 0. 1 8 nmoles corticosterone/min/mg protein). Therefore, at 25 dayspostoperatively, cholesterol SCC activity has been restored in the ARH group whilellβ-hydroxylase activity remains impaired.