FIGURE 1.

Extracellular UDP-sugars regulate HAS2 expression and hyaluronan synthesis. A, HaCaT cultures were treated for 2 h with 100 μm of the indicated UDP-sugars and analyzed for HAS2 expression. B, UDP-Glc as the most powerful stimulator was used to study hyaluronan release into growth medium, analyzed 4 and 6 h after adding UDP-Glc. C, the time course of HAS2 induction using 100 μm concentration of UDP-Glc. D, effect of UDP-Glc concentration on HAS2 expression during a 2-h incubation. In panels A and C the data represent mean ± S.E. of three independent experiments, each done as duplicate. The statistical significance of the differerences between control and UDP-sugars were tested using Dunnett's test. In panels B and D the data represent mean ± S.E. of 5 and 4 independent experiments, respectively. Statistical significance was estimated using paired sample t test. *, p < 0.05; **, p < 0.01; and ***, p < 0.001.