Selenium and vitamin E are known to be essential nutrients for many species of animals; they have also been implicated in several problems in human health. Recent studies have provided good evidence of at least some of the biochemical functions of selenium and vitamin E, understanding of which is necessary to evaluate fully their roles in human nutrition and health. The selenium- and vitamin E-deficient chick has been established in this laboratory as a useful animal model for investigating the biochemical mechanisms of action of selenium and vitamin E. We propose to use the chick to determine the biochemical basis for the specific function of selenium in maintaining pancreatic exocrine function, a function which may be independent of the role of selenium in glutathione peroxidase. Specifically, we propose to determine whether selenium functions in the pancreas (a) to affect the activity of the selenium-dependent glutathione peroxidase, (b) to affect the subcellular distribution of selenium in the pancreas, and (c) for respiratory control of oxidative phosphorylation. We seek to determine which biochemical lesions in the chick pancreas may precede decreases in the activity of Se-GSHpx. We will employ established biochemical techniques including determinations of Se-GSHpx; lipoyl dehydrogenase; cell marker enzymes; incorporation of radio-labeled precursors into DNA, RNA and protein; respiratory control of oxidative phosphorylation. Because all biochemical studies will utilize nutritionally controlled and monitored animals, results will be evaluated relative to the performance of the intact animal.