DETERMINATION OF PLASMA ACTIVITIES OF PURINE NUCLEOSIDE PHOSPHORYLASEBY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY - ESTIMATES OF NONPARENCHYMAL CELL INJURY AFTER PORCINE LIVER-TRANSPLANTATION

An assay is described for measurement of purine nucleoside phosphoryla se (PNP) in plasma by high-performance liquid chromatography (HPLC). A plasma sample was incubated with hypoxanthine and ribose-1-phosphate in phosphate-free medium at pH 7.4 to catalyse the production of inosi ne by plasmatic PNP. The reaction was stopped by addition of perchlori c acid to inactivate the enzyme and to precipitate plasma proteins. Af ter centrifugation and neutralization of the supernatant with NaOH the increase in the substrate inosine was determined by HPLC. Plasma acti vities of PNP averaged 5.0 mU/ml before and 12.3 mU/ml (p <0.001), 5 m in after porcine liver transplantation. At the same time points, the p lasma activities of the frequently used liver enzymes lactate dehydrog enase or alanine aminotransferase remained virtually unchanged. Thus, plasmatic activities of PNP may be a suitable and early indicator of i schemic alterations to the graft in vivo.