Variation of the morphology of xanthine crystals due to the presence of some methylxanthines.

Scanning electron microscopy images of xanthine crystals obtained in synthetic urine containing 400 mg/L xanthine, and incubated 24 h at 37 oC, in the presence of different inhibitors as follows: (A) without inhibitors; (B) with 20 mg/L 3-MX; (C) with 40 mg/L 3-MX; (D) with 20 mg/L 7-MX; (E) with 40 mg/L 7-MX; (F) with 20 mg/L 3-MX and 20 mg/L 7-MX and (G) and (H) with 20 mg/L 3-MX and 40 mg/L 7-MX.