Abstract
Substrate induced difference spectra in microsomes from 3-methylcholanthrene treated rats were investigated using substrates which cause type I difference spectrum in microsomes from control rats. It was found that α, α'-dipyridyl showed only type II spectrum, whereas SKF 525-A and ethylmorphine produced type I spectra. Additionally, hexobarbital, aminopyrine and imipramine produced type I spectra when they were used by rather low concentrations but type II spectra were induced by high concentrations of them.α, α'-Dipyridyl caused type II spectrum when microsomes from control rats were treated with phospholipase C. The type II spectrum of α, α'-dipyridyl in 3-methylcholanthrene-induced microsomes was increased by treatment with phospholipase C.
Moreover, α, α'-dipyridyl showed type II spectrum in microsomes from control rats when SKF 525-A, which has a high affinity to combine with type I binding site of P-450, was added into reference and sample cuvettes.
From above data, the authors concluded that most of type I compounds could combine with both type I and type II binding sites, and discussed on the properties of type I and type II binding sites.
