Figure 4.

Uptake of carnosine into erythrocytes protects it from degradation by serum carnosinase as revealed by intra- and extracellular concentrations of carnosine in erythrocytes cultivated in the presence of human serum. Erythrocytes of a healthy volunteer (male, age 29) were incubated in the presence of 40% human serum or 40% FBS and 0, 3, or 6 mM carnosine. After 4 h of incubation and before the start of the experiment (0 h) the concentration of carnosine and l-histidine in the medium (black bars, a,b) and the erythrocytes (c,d) were determined. (Note: no bars are seen indicating extracellular concentrations of carnosine after 4-h incubation in humans (panel a) because the concentration is already below detection limit after this incubation time due to carnosinase activity). All measurements were performed in triplicate; statistical significance was performed by one-way ANOVA with Games–Howell post hoc test: ns: not significant; * p < 0.05; ** p < 0.005; *** p < 0.0005.