Oral administration of l-ornithine increases the content of both collagen constituting amino acids and polyamines in mouse skin

Abstract

l-Ornithine is found in animals as a free amino acid and is a vital component of the urea cycle in the liver; it is reported to have various functions such as promoting wound healing, promoting growth hormone secretion, hypnotic effects, and so on. The present study aimed to investigate the effects of a single oral administration of l-ornithine on 1) the metabolism of amino acids in the liver and skin of mice and 2) the metabolism of polyamines in the skin of mice. To this end, ICR mice were separated into five groups; four groups were administered l-ornithine dissolved in fresh water (3.0 mmol/10 ml/kg) and a fifth group, the control, was not administered l-ornithine. The four groups comprised mice sampled at specific times (30, 60, 120 and 180 min) after oral administration of l-ornithine. We found that metabolism of l-ornithine to l-citrulline was rapid and that l-citrulline concentration remained high in mice sampled at later stages. Similarly, the concentrations of l-proline and glycine, both of which are important components of collagen, also rapidly increased in the skin following l-ornithine treatment. The concentrations of polyamines (putrescine, spermidine and spermine), which are known to increase the synthesis of certain proteins and enhance the epidermal barrier function, were also significantly increased in the skin. Our study shows that oral administration of l-ornithine significantly influences the chemical composition of the skin of mice through increases in both amino acids and polyamines after a short period of time.

Keywords: Collagen constituting amino acids; Metabolic changes; Polyamines; l-citrulline; l-ornithine.