A COMPARISON OF HPLC AND TERNARY COMPLEX-BASED ASSAYS OF TISSUE REDUCED FOLATES

Two different analytical methods were used to estimate reduced folates from the same cultured hepatoma cell preparation. A method based on HPLC separation of reduced folate pools in cells prelabelled with [H-3]-folic acid was compared to a method based upon quantitative assessment of bound radioactive ligand by gel filtration after entrapment of one reduced folate, methylenetetrahydrofolate, into a stable ternary complex with thymidylate synthase and [H-3]-fluorodeoxyuridine monophosphate. In this second method additional folate pools were measured following enzymatic conversion to methylenetetrahydrofolate. Results show completely satisfactory agreement between the two methods both in terms of total folate content and in levels of individual folate pools.