The 'nothing dehydrogenase' reaction and the detection of ischaemic damage

The 'nothing dehyrogenase' reaction is defined as the reduction of tetrazolium salts in media lacking specific substrates for dehydrogenases. In this investigation, the kinetics of the 'nothing dehydrogenase' reaction were studied in cryostat sections of rat heart and liver with the use of various polyvinyl alcohol-containing incubation media. Formazan production was measured at 585 nm with a cytophotometer. The 'nothing dehydrogenase' reaction was substantially lower in the heart than in the liver which was due to low levels of endogenous lactate and the absence of proteins containing thiol groups, such as albumin, in the heart. In vitro ischaemia resulted in a reduced 'nothing dehydrogenase' reaction due to loss of NAD+, possibly as a consequence of its breakdown by glycohydrolase activity. One hour reperfusion following one hour ischaemia caused a decreased 'nothing dehydrogenase' reaction in certain areas of the liver. This reduction was a result of leakage of lactate dehydrogenase and thiol-containing molecules. It appeared at the ultrastructural level that parenchymal and endothelial cells were heavily damaged in the areas containing a low 'nothing dehydrogenase' activity. In conclusion, early ischaemic damage in liver can be detected with the 'nothing dehydrogenase' reaction.