1. Department of Nephrology, Transplantology and Internal Medicine, Medical University of Gdansk, Debinki 7 Str., 80-211 Gdansk, Poland
2. Department of Biochemistry, Medical University of Gdansk, Debinki 7 Str., 80-211 Gdansk, Poland
3. Department of Renal Medicine, Guy's Hospital, London SE1 9RT, U.K.
4. Purine Research Unit, Guy's Hospital, London SE1 9RT, U.K.