The Stability of Triphosphopyridine Nucleotide and Its Reduced Form in Rat Liver.

It has been quite generally accepted that reduced triphosphopyridine nucleotide (TPNH) exceeds TPNf in most tissues by a factor of 10 or more, although DPNH is ordinarily much lower than DPN+. The reputed predominance of TPNH has stimulated widespread interest because of its role in lipid formation and in many other reductive synthetic processes (1). In studies from this laboratory (2, 3) data were obtained which indicated that TPN+ levels may be considerably higher than those previously accepted. Therefore, it seemed worthwhile to make a considerable effort to determine what the real levels of TPN+ and TPNH in liver may be. This report describes how TPNf and TPNH are affected by post-mortem changes and by various methods of handling and extraction of samples, and particularly how TPNf in fresh liver is affected by mild or strong acid treatment. The results indicate that TPN+ as it exists in fresh tissues is very sensitive to destruction by strong acid; that if extraction with mild acid gives true levels, the ratio of TPN+ to TPNH for four tissues examined is nearly 1; and that DPN+ is not affected in the same way as TPN’ by strong acid.