Pyrimidine-enhanced purine uptake in hepatocytes and improved survival from hypovolemic shock

To assess the effect of pyrimidines on the incorporation of purines into rat hepatocytes, monolayer preparations of hepatocytes were incubated with radiolabeled precursors and their uptake determined. The uptake of purine precursors (inosine monophosphate, inosine, and hypoxanthine) was 27.8 +/- 1.31 nmoles per well, per 30 min. In the presence of added pyrimidines (uridine monophosphate, uridine, and orotate), this increased by 22%. Further enhancement (45%) was observed when L-dihydroxyphenylalanine (L-DOPA) plus pyridoxal-5'-phosphate was added to the purine/pyrimidine incubation medium. The effect of increased uptake of purines on survival after hypovolemic shock was also studied. Rats were bled to a blood pressure of 40 mmHg for 105 min and then treated with return of shed blood plus saline with or without purines and pyrimidines. Survival at 24 hr was 43% (15/35) in control animals, 66% (8/12) (P = 0.276) when treated with inosine monophosphate (IMP) and aspartate (60 mumoles/kg each), and 83% (10/12) (P = 0.037) for IMP with aspartate and orotate treatment (60 mumoles/kg each). Thus, the addition of orotate enhanced survival possibly by promoting salvage or by uptake of purines. Nucleotide concentrations in the livers of animals after shock which had received IMP and orotate demonstrated a return of both ATP and energy charge to normal, further indicating the value of this treatment.