Comparative effects of scopoletin and aflatoxin B1 on bovine hepatic mitochondrial respiration in vitro

A comparative study of the in vitro effects of the coumarin compounds, scopoletin and aflatoxin B1 (AFB1), on bovine (Bos indicus) hepatic mitochondrial respiration was carried out polarographically, using isocitrate -NAD+ (3 - site), succinate (2 - site), and reduced cytochrome c (1 - site), as respiratory substrates. Both scopoletin and AFB1 elicited a substrate--dependent stimulation or inhibition of the mitochondrial states 4 and 3 respiration. The results suggest that AFB1 has a higher tendency to inhibit the mitochondrial respiration than scopoletin, while scopoletin showed higher uncoupling effects than AFB1. The effects of scopoletin and AFB1 on mitochondria were more pronounced on the electron transport than on phosphorylation reaction. The extent (3-35%) of AFB1 induced inhibition of bovine mitochondrial respiration observed in this study, was appreciably lower than the values indicated in other animal species (rats and guinea fowls) reported in previous studies using equivalent concentrations of the toxin. These results were discussed in terms of the susceptibility of the animal species to the toxic effects of scopoletin and AFB1.