The sensitivity of mitochondrial Mg2+ ATPase to DDT and analogs at different temperatures

Oligomycin-sensitive (O-S) Mg²⁺ ATPase from American cockroach muscle was more sensitive to DDT, TDE, methoxychlor, and DDE at cool temperatures than at warm temperature, thus showing a negative temperature effect. In contrast, inhibition by acaricides dicofol, chlorfenethol, and Plictran shows a positive temperature effect. Oxidative phosphorylation in a mitochondrial preparation from cockroach coxal muscle was reduced by DDT, but the reduction was greater at a higher temperature (32°C) than at a cooler temperature (22°C). In addition, Na⁺K⁺ ATPase from cockroach nerve cord showed a positive temperature effect with DDT. The inhibition by DDT was much less on Na⁺K⁺ ATPase than on O-S Mg²⁺ ATPase. The negative temperature effect by DDT and analogs on O-S Mg²⁺ ATPase parallels toxicity effects on insects and fish as reported by numerous researchers. The results provide further evidence for this energy-regulating enzyme being a critical component in the biological action of DDT.