Tritium as a Tracer for Reducing Equivalents in Isolated Liver Cells

Abstract

1 Isolated liver parenchymal cells were incubated with lactate or other glucogenic substrates together with tracer levels of various tritiated substrates. The tritium yields in glucose and water were determined, as well as the distribution of tritium in the glucose molecule. 2 Substrates of mitochondrial dehydrogenases give lower specific yields in glucose and a higher percentage of glucose tritium on C-6, than do cytosolic substrates. d-[3-3H]- and l-[3-3H]-hydroxybutyrate and l-[2-3H]glutamate represent typical mitochondrial substrates while l-[2-3H]-lactate, [2-3H]glycerol and [2-3H]sorbitol represent typical cytosolic substrates. 3 The results with [1R-3H]ethanol and [1S-3H]ethanol indicate that ethanol is oxidized mainly by the cytosolic alcohol dehydrogenase to acetaldehyde, which then is oxidized predominantly in the mitochondria. However, a significant proportion of ethanol oxidation may also occur via a system not involving alcohol dehydrogenase.