Enzyme changes during experimental silicotic fibrosis: II. Intermediary metabolism enzymes of the lungs

The activity of seven important enzymes of intermediary metabolism in lung tissues was monitored during the development of experimental silicosis in rats. The enzymes were triosephosphate dehydrogenase (TPDH), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glycerol-3-phosphate NAD dehydrogenase (GPDH), hexokinase (HK), citrate synthase (CS), and hydroxyacyl-CoA dehydrogenase (HOADH). Changes were compared with the lung tissue response to nonfibrogenic corundum dust and with healthy lung tissues. In the developing silicotic lung tissue important disproportional activity changes take place in some enzymes (HK, TPDH, LDH, GPDH, HOADH); different, possibly less important changes occur after corundum application. The lung tissues of silicotic rats have an enhanced capacity for anaerobic degradation of saccharides with lactate as the end product. This finding can be related to the activation of collagen prolyl hydroxylase. The maximum changes in enzyme activities occur in the 2nd week of dust application.