Similarity of isozyme pattern of serum lactate dehydrogenase following treatments with O,O,S-trimethyl phosphorothioate and paraquat.

Oral administration of O,O,S-trimethyl phosphorothioate (OOS-TMP) causes delayed mortality and lung injury in rats. The present study was carried out to determine whether serum lactate dehydrogenase (LDH) activity and its isozyme pattern were capable of detecting lung injury and possible other organ damages caused by OOS-TMP. Carbon tetrachloride (CCl4, 1 ml/kg, i.p., 24 h) and paraquat (25 mg/kg, i.p., 48 h) were selected as standard chemicals for liver injury, and lung and kidney injuries, respectively. The activity of serum LDH increased to 4 times above control following treatment of rats with OOS-TMP (20 mg/kg, p.o., 72 h). Treatment with CCl4 increased the activity to 8 times while paraquat only slightly increased the activity. Isoelectrophoresis of serum samples showed that OOS-TMP increased the activities of isozymes LDH 1 and LDH 2. This isozyme pattern was similar to the pattern of paraquat but quite different from the pattern in animals treated with CCl4, where LDH 5 was most predominant, or in control animals. Thus, the isozyme pattern strongly suggests that OOS-TMP causes the similar organ damage evoked by paraquat, lung and kidney.