REDUCED GLUTATHIONE INHIBITS RABBIT AND RAT SKELETAL-MUSCLE LACTATE-DEHYDROGENASE AND PREVENTS DINITROPHENOL INDUCED EXTRACELLULAR ACIDIFICATION BY AN EPITHELIAL-CELL LINE

Glutathione (GSH) is a tripeptide synthesised enzymatically from its c omponents amino-acids by unicellular and multicellular organisms. GSH acts as a cellular anti-oxidant, protects the structural configuration of some enzymes, is involved in erythrocyte function and plays a role as co-enzyme in several reactions. We have found that GSH inhibits pu rified lactate dehydrogenase (1.56 U LDH /ml) from rabbit skeletal mus cle after 6 min pre-incubation with an ED50 of about 5.4 mu M. The inh ibition is time dependent with a maximum after 45 minutes preincubatio n. Buffer (5 x 10(-2) M TRIZMA hydrochloride, pH 7.4) and a chelator ( 2 x 10(-3) M EDTA) in the pre-incubation solution did not prevent the inhibition. Prolonged dialysis was almost without effect on GSH-inhibi ted LDH activity solution, indicating either an irreversible or a very tight binding inhibition. Kinetic analysis showed that this inhibitio n is of a very tight binding and at the same time of the uncompetitive type. GSH also inhibits LDH activity of rat M. soleus and M. gastrocn emius homogenates. This effect is probably unrelated to the reducing p roperty of GSH since dithioerythritol (0.17-1.34 mM) does not mimic it . Loading of MDCK cells with glutathione ethylester completely prevent ed the acidification induced by 2,4-dinitrophenol, suggesting that GSH may influence the glycolytic pathway in vivo.