Abstract
FAD, as one of the ester-forms of riboflavin, is formed by FAD pyrophos-phorylase from FMN and plays an important role as a coenzyme in the oxidoreduction system. Various physiological actions of FAD have been investigated using rats. The induction of adrenal atrophy in rats treated with dexamethasone phosphate was partially prevented by the simultaneous administration of FAD. Electronmicroscopic study showed that the number of organelles and fat droplets, the shape of the nuclei in the fascicular zone, the decrease of glucose-6-phosphate dehydrogenase activity and the turnover of ^<32>P in the cell fractions of adrenals were normalized by FAD administration compared to dexamethasone alone. The ^<32>P turnover in the adrenal-microsomal fraction in the dexamethasone treated rats increased remarkably by simultaneous administration of FAD and ACTH. The finding suggests a synergistic effect between FAD and ACTH. The decreased synthesis of cortisol-binding protein in the lens by dexamethasone phosphate was restored by FAD administration probably due to promotion of mRNA turnover. The stimulation effect of in vitro FAD on rat lenticular glutathione reductase represents a sensitive indicator of the riboflavin nutritional status as well as the activity coefficient of glutathione reductase in human and rat erythrocyte.
