Effect of the cold environment on organophosphate toxicity and inhibition of cholinesterase activity.

1. Rats were used for studies on organophosphate (OP) toxicity both in acute and chronic cold exposure. Furthermore the effects of OPs on tissue acetyl- and butyrylcholinesterase activities were studied in the cold environment. 2. No change in the toxicity of dichlorovinyl phosphate (DDVP) was observed whereas that of diisopropylphosphofluoridate (DFP) increased 1.5-fold at +5 degrees C. 3. Chronic exposure to cold produced no change in DFP toxicity. 4. The survival time in acute cold exposure (1.1 x LD50 DFP) was longer than in chronic exposure or at +20 degrees C. 5. In control rats, chronic cold exposure increased blood BuChE and decreased BuChE in lungs. 6. A dose-dependent inhibition of cholinesterases was observed. 7. AcChE in the liver of chronically cold exposed rats was more sensitive to DFP inhibition compared to acute exposure. 8. Blood AcChE activity correlated only to AcChE in brain and lungs in rats.