Pyridine coenzymes of subcellular tissue fractions.

The levels of pyridine nucleotides in tissues have been the subject of a large number of reports. Much interest has been focused on the ratios of oxidized to reduced coenzymes in different pathological conditions (1). Recently, Glock and McLean (2) have reported the important observation that reduced TPN is present in whole rat liver in comparatively large amounts, whereas the concentration of the oxidized form of TPN was found to be very low.’ On the other hand, oxidized DPN was found to be present in an excess over the reduced form. Sensitive fluorometric procedures have recently been developed for the assay of different forms of the pyridine nucleotides (3). This has made possible an analysis of the subcellular tissue fractions. The present communication deals with the concentrations of DPN, DPNH, TPN, and TPNH in various cellular fractions and the factors which influence the levels of pyridine coenzymes in these fractions. This report will show that the most of the TPNH in rat liver is localized in the mitochondria.