Now Arginine & Citrulline – With 500mg Arginine ^ 250mg Citrulline! Support Protein Metabolism & Helps Maintain Muscle Tissue!Support Protein Metabolism & Helps Maintain Muscle Tissue!Arginine and Citrulline are two amino acids that are integral to protein metabolism and utilization, as well as to the maintenance of muscle tissue. Both are key intermediates in the urea cycle, where they participate in the detoxification of ammonia via the production of urea. Arginine that has not been converted to urea enters general circulation where it is distributed to various tissues and metabolized for other uses such as protein synthesis. Scientific studies have shown that supplementing Citrulline along with Arginine helps maintain nitrogen balance better than supplementation with Arginine alone. Note: Manufacturers continually change product specifications. While we try our best to keep product descriptions up to date, they do not necessarily reflect the latest information available from the manufacturer. We are not responsible for incorrect or outdated product descriptions and/or images.