Effects of L-Ornithine on metabolic processes of the urea cycle in human keratinocytes.
The complex metabolic function of L-ornithine has led to a great interest in studying its pharmacotherapeutic potential. L-Ornithine is known to be crucial for the metabolism of keratinocytes, especially in the synthesis of urea, polyamines and precursors of collagen synthesis. In this study, we investigated in vitro the cytotoxicity of L-ornithine, and its influence on urea synthesis and arginase expression in primary human keratinocytes. L-Ornithine (> or =1 mM) induced a decrease in the de novo urea synthesis of keratinocytes and an increase (> or =10 mM) in the expression of the urea-generating enzyme arginase. Up to 20 mM, L-ornithine showed no cytotoxic potential, whereas higher concentrations induced apoptosis in keratinocytes in a concentration- and time-dependent manner.