EFFECT OF GLUCAGON ON THE PLASMA-CONCENTRATION OF URIDINE

To determine whether glucagon affects the plasma concentration of urid ine, we administered 100 mL physiological saline containing 1 mg gluca gon or 100 mt physiological saline alone intravenously over 1 hour to healthy subjects. Glucagon decreased the plasma concentration of uridi ne from 5.72 +/- 1.05 to 4.80 +/- 0.60 mu mol/L but increased the conc entrations of cyclic adenosine monophosphate (cAMP) in plasma and pyru vic acid and lactic acid in blood 59-, 1.4-, and 1.3-fold, respectivel y. Although glucagon increased urinary excretion of uric acid, it did not affect the plasma concentration of purine bases (hypoxanthine, xan thine, and uric acid) or urinary excretion of oxypurines and uridine, indicating that glucagon does not affect purine degradation and sugges ting that glucagon does not affect adenosine triphosphate (ATP) consum ption-induced pyrimidine degradation. In contrast, physiological salin e did not affect any of the measured variables. These results suggest that glucagon enhanced Na+-dependent uridine uptake from the blood int o the cells, since glucagon stimulates Na+-dependent uridine uptake in to cells in vitro. Copyright (C) 1998 by W.B. Saunders Company.