Studies on selenium incorporation into, and electron-transfer function of, liver microsomal fractions from normal and vitamin E-deficient rats given phenobarbitone.

1. The incorporation of (75)Se from Na(2) (75)SeO(3) into the liver endoplasmic reticulum of rats given phenobarbitone was investigated by using a zonal centrifuge technique. 2. It was found that, in rats deprived of vitamin E, or of vitamin E and selenium, phenobarbitone was without effect on the incorporation of (75)Se or on its conversion to (75)Se(2-). When vitamin E was given at the same time as the phenobarbitone and (75)Se, there was a large increase in the amount of (75)Se and (75)Se(2-) found in the smooth reticulum. It is concluded that there may be a specific vitamin E-dependent role for selenium and selenide in the smooth endoplasmic reticulum, and it is suggested, in the light of these and other observations, that the selenide may form a part of the active centre of a non-haem iron-containing protein ;X', that may function in microsomal electron transport. 3. Measurements of the contents of cytochromes P-450 and b(5) in liver microsomal fractions of rats given vitamin E-deficient, and vitamin E- and selenium-deficient diets, showed that haemoprotein biosynthesis is unimpaired in these rats and phenobarbitone treatment resulted in the expected increase in the haemoproteins. 4. When the reduction of cytochrome P-450 by NADH and NADPH was measured, no difference was found between normal and deficient animals. 5. These results are discussed in relation to current knowledge of microsomal electron transfer.