Orally administrated D-arginine exhibits higher enrichment in the brain and milk than L-arginine in ICR mice

• Published in: Journal of Veterinary Medical Science Vol. 82; no. 3; pp. 307 - 313
• Main Authors: ASO, Kenta, NISHIGAWA, Takuma, NAGAMACHI, Satsuki, TAKAKURA, Mayumi, FURUSE, Mitsuhiro
• Format: Journal Article
• Language: English
• Published: Japan JAPANESE SOCIETY OF VETERINARY SCIENCE 2020; Japan Science and Technology Agency; The Japanese Society of Veterinary Science
• Subjects: Amino acids; Arginine; brain; Cerebral cortex; D-Amino acids; enrichment; Growth hormones; Hypothalamus; Infants; Metabolites; mice; Milk; Oral administration; Physiology; milk; enrichment; arginine; brain; mice
• ISSN: 0916-7250; 1347-7439
• DOI: 10.1292/jvms.19-0630

D-Amino acids exert various physiological functions and are widely present in animals. However, they are absorbed to a lesser extent than L-amino acids. Little is known about D-arginine (D-Arg); however, its isomer L-Arg serves as a substrate for several metabolites and exhibits various functions including promotion of growth hormone secretion. Milk is the only nutrient source for infants; it plays an important role during their initial growth and brain development. No studies have evaluated the availability of D-Arg in the brain and milk in mammals. Here, we have studied the differential availability of orally administered D- and L-Arg in the brain and milk using ICR mice. Our results revealed that without D-Arg administration, D-Arg was undetectable in both plasma and brain samples. However, the plasma D-Arg was about twice the concentration of L-Arg post administration of the same. In the cerebral cortex and hypothalamus, L-Arg concentration remained almost constant for over period of 90 min after L-Arg treatment. Nevertheless, the L-Arg concentration decreased after D-Arg administration with time compared to the case post L-Arg administration. Contrastingly, D-Arg level sharply increased at both the brain regions with time after D-Arg treatment. Furthermore, L-Arg concentration in the milk hardly increased after L-Arg administration. Interestingly, oral administration of D-Arg showed efficient enrichment of D-Arg in milk, compared with L-Arg. Thus, our results imply that D-Arg may be available for brain development and infant nourishment through milk as an oral drug and/or nutrient supplement.