Mice, Rats and Guinea Pigs Exhibit Significant Variations in the Plasma, Urine and Tissue Levels of Taurine, Betaine, Sarcosine and Other Osmolyte-Active Amino Acids.

BACKGROUND: Osmolytes are naturally occurring compounds that protect cells from osmotic stress in high-osmolarity tissues, such as the kidney medulla. Some amino acids, including taurine, betaine, glycine, alanine, and sarcosine, are known to act as osmolytes. This study aimed to establish the levels of these amino acids in body fluids and tissues of laboratory animals used as models for human diseases in biomedical research.

METHODS: Liquid chromatography coupled with mass spectrometry was used to quantify taurine, glycine, betaine, alanine, beta-alanine, and sarcosine in plasma, urine, and tissues of adult, male mice, rats and guinea pigs.

RESULTS: Among the species analyzed, taurine was found to have the highest tissue concentrations across all compounds, with the heart containing the greatest amount. In guinea pigs, betaine levels were higher in the renal medulla than in the renal cortex ( p < 0.01), while in rats and mice, there were no significant differences in betaine levels between the kidney cortex and medulla. The urine of guinea pigs had lower levels of sarcosine compared to rats ( p < 0.001), while the plasma ( p < 0.05; > 0.05), heart ( p < 0.05; < 0.05), lungs ( p < 0.01; < 0.01), liver ( p < 0.001; < 0.05), and kidneys ( p < 0.01; < 0.01) of rats exhibited notably higher concentrations of sarcosine compared to both mice and guinea pigs, respectively.

CONCLUSIONS: There are pronounced differences in the concentrations of taurine, betaine, and other amino acids across the investigated species. It is important to acknowledge these differences when selecting animal models for preclinical studies and to account for variations in amino acid concentrations when selecting amino acids doses for interventional studies.