L‐type Ca 2+ channel current is controlled by ROS regulated by glucose‐6‐phosphate dehydrogenase and mitochondrial respiratory chain complex I (698.2)

H 2 O 2 moderately inhibits L‐type Ca 2+ channel current ( I Ca,L ) and dithiothreitol (DTT), a reducing agent, reverses I Ca,L inhibition in rat aorta‐derived A7r5 cells. This suggests that oxidation of thiol on Cav1.2 protein by H 2 O 2 , at least partly, contributes to the inhibition of I Ca,L . Furthermore, the whole‐cell I Ca,L recorded with 10 mM‐Ba 2+ as a charge carrier and evoked by a depolarization step repetitively at 1/20 s are completely suppressed by ebselen (3 μM). This suggests that S‐glutathionylation of Ca V 1.2 might also be potentially involved in the H 2 O 2 ‐induced inhibition. 6‐Aminonicotinamide (6‐AN; 1 mM), an inhibitor of glucose‐6‐phosphate dehydrogenase (G6PD) that blocks reduction of NADP + to NADPH and GSSG to GSH and O 2 ‐ production from NADPH‐oxidase, inhibited I Ca,L by 18% in 5 min. Rotenone (Rot), an inhibitor of mitochondrial complex I that reduces O 2 ‐ in a tissue specific manner, rapidly but transiently augmented I Ca,L amplitude in a dose‐dependent manner (10 nM‐10 μM), and increased I Ca,L up to 30% at 10 μM. But, it subsequently accelerated the time course of inactivation. The 6‐AN‐induced inhibition of I Ca,L suggests that NADPH generated by G6PD contributes to sustain normal I Ca,L by reducing S‐glutathionylation induced by H 2 O 2 . While, Rot‐induced reduction of mitochondrial H 2 O 2 potentially removes its basal inhibitory action on Ca V 1.2 and this increases I Ca,L in the presence of G6PD‐derived NADPH. In conclusion, our results indicate that basal I Ca,L magnitude is regulated by extra‐mitochondrial and mitochondrial redox.