The purpose of this proposal is to study the metabolism of ammonia in the lens of the eye. Amino acids accumulate in the lens by a number of active transport systems. They are utilized for biosynthetic reactions and can also enter into several metabolic pathways, including transamination, deamidation, and oxidative deamination. These reactions directly or indirectly lead to the formation of ammonia in the lens. Several possible pathways exist for utilization or detoxification of this ammonia, including synthesis of glutamate by glutamate dehydrogenase, synthesis of glutamine by glutamine synthetase, or urea synthesis by the urea cycle. Various combinations of glutamate synthesis with transamination reactions may result in formation of amino acids such as aspartate or alanine. The literature contains supporting data for the presence of the enzymes necessary for any or all of these pathways to be active in the lens. It is proposed to study ammonia metabolism in the lenses of calves, rabbits and rats. The activities and locations of several of the enzymes involved with ammonia fixation will be determined, and the relative contribution of each to the overall nitrogen economy of the lens of each species will be estimated based on the availability of the necessary enzymes and the kind and amount of product formed under various experimental conditions. Enzymes will be assayed in lens homogenates using standard methods, and the products accumulated by lenses will be measured in lens culture.