Increase of protein synthesis by uridine supplement in lectin-stimulated peripheral blood lymphocytes and EB virus-transformed B cell line of hereditary orotic aciduria type I.

A 2 month-old Japanese girl with hereditary orotic aciduria type I was treated with oral uridine supplement. The activities of orotate phosphoribosyltransferase (OPRT) and orotidine-5'-phosphate decarboxylase (ODC) in erythrocytes were 2.7 and 0.4%, respectively, of those in the controls. Megaloblastic anemia, excessive urinary excretion of orotic acid, lymphopenia and decreased number of OKT3 positive lymphocytes on admission were corrected after the uridine supplement. Peripheral blood lymphocytes (PBL) were cultured for 24 hr in RPMI 1640 medium with 10% heat-inactivated fetal calf serum and further stimulated with PHA-P, ConA or PWM in the presence of 10 to 1000 microM uridine. EB virus-transformed B cell line (LCL) maintained with an optimal concentration of uridine was cultured for 48 hr in uridine free medium and cultured for an additional 48 hr with 1 to 1000 microM uridine. The incorporations of leucine in to PHA-, ConA- and PWM-stimulated PBL and into LCL of the patient increased in the presence of uridine over 10 microM, although they did not increase in controls. These data suggest that low protein synthesis might correlate with an immune deficiency in hereditary orotic aciduria type I.