Further studies on corticosteroidogenesis IX. Energy-linked transhydrogenase in rat adrenal gland mitochondria

Abstract

While malonate inhibited succinate-supported 11β-hydroxylation of 11-deoxy-corticosterone in rat adrenal mitochondria, it had no effect on the utilization of α-ketoglutarate for this purpose. Addition of 5 mM Amytal in the presence of α-ketoglutarate and deoxycorticosterone led to an inhibition of respiration and a greatly diminished corticosterone production. Addition of succinate to this Amytal-blocked α-ketoglutarate system, reestablished O 2 consumption and corticosterone production. Rotenone, 10 μM, had only a slight effect on succinate or α-ketoglutarate supported 11β-hydroxylation and respiration. It would appear that rotenone which is known to inhibit NADH oxidation in mitochondria from most mammalian cells at this concentration behaves differently in rat adrenal mitochondria. The findings obtained in the experiments with Amytal indicate participation of an energy-linked transhydrogenase enzyme involved in reaction(s) leading to the oxidation of NADH and generation of NADPH, which is necessary for 11β-hydroxylation of deoxycorticosterone. It is postulated that in the Amytal-inhibited systems ATP or high energy compounds generated by the aerobic oxidation of succinate over the uninhibited part of the respiratory chain serve as the source of energy for the transhydrogenase enzyme.