Zonal distribution of cytochrome P-450s (P-450 11β and P-450 scc) and their relation to steroidogenesis in bovine adrenal cortex

Abstract

Zona glomerulosa and zonae fasciculata-reticularis of bovine adrenal cortex were separated by our improved method using a remodeled microtome. A considerable amount of fresh mitochondria and microsomes was quickly obtained. Specific content of cytochrome P-450 in the mitochondria was higher in zonae fasciculata-reticularis than in zona glomerulosa. When metyrapone was added to the mitochondria and the drug-induced difference spectra were measured, there appeared two phases in the titration curve; the first phase was saturated at a concentration of 3 μM and the second phase appeared at concentrations higher than 10 μM. The first phase seemed to be due to the substrate-free P-450 11β and the second phase to the cholesterol-bound P-450 scc. From these spectral studies contents of cytochrome P-450 scc and P-450 11β were estimated, and those were found to be equal for each zone. From similar studies on substrate-induced difference spectra, there seemed to be no difference between two zones in the affinity of cytochrome P-450 11β for deoxycorticosterone and 11-deoxycortisol. This was also the case with 11β-hydroxylase activity and substrate specificity for deoxycorticosterone and 11-deoxycortisol.