L. K. Cutkomp

ATPase activity in fish tissue homogenates and inhibitory effects of DDT and related compounds

Abstract The specific activities of ATPases in homogenates of bluegill fish tissues were determined and found to be similar to those previously reported for rabbit tissues. Na+-K+ ATPase was most active in brain and kidney, and Mg2+ ATPase was most active in muscle. A prominent inhibition of Mg2+ ATPase by DDT and TDE tested in vitro was found in tissue homogenates of fish muscle; inhibition was also found in brain, kidney and liver. Less effective, when compared at low concentrations, were DDE, o,p′-DDT and dicofol. DDA was inactive and methoxychlor had little effect. Dicofol was the only closely related compound which had a greater effect on Na+-K+ ATPase of the brain than on Mg2+ ATPase. A synergistic effect resulted when DDT and dicofol were combined, producing greater inhibition of muscle ATPases. Selected chlorinated hydrocarbons of the cyclodiene group also showed inhibitory effects, with Na+-K+ ATPase inhibition being almost equal to Mg2+ ATPase inhibition. Epoxides of the selected cyclodienes were less effective inhibitors of the enzyme system. The significance of these findings are discussed in relation to enzyme inhibition and toxicity of DDT and other compounds.

A comparison of DDT and its biodegradable analogues tested on ATPase enzymes in cockroach

Abstract Analogues of DDT (ethoxymethyl and methoxymethio derivatives) compared with DDT for their inhibitory action on the ATPase system from tissues of the cockroach, Periplaneta americana show similar, but less inhibitory effects. The mitochondrial (oligomycin-sensitive) Mg2+ ATPase activity from coxal muscle preparations was more sensitive to DDT than the two analogues; whereas, the muscle and nerve cord homogenates showed about equal sensitivity to the biodegradable analogues. The mitochondrial Mg2+ ATPase from nerve cord preparation was more sensitive to the three compounds than the Na+K+ ATPase activity. The significance of these results in relation to recent reports on the effect of DDT on Na+K+ ATPase is discussed.

Inhibition of oligomycin-sensitive (mitochondrial) Mg2+ ATPase by DDT and selected analogs in fish and insect tissue☆

Abstract Mitochondrial (oligomycin-sensitive) Mg 2+ ATPase from cockroach muscle is shown to have a very high sensitivity to DDT when compared to fish brain preparations and to inhibition of the same enzyme system by dicofol. In vitro inhibition was 10% at 7 ppb DDT, while dicofol required 1110 ppb for 10% inhibition of a cockroach muscle preparation. However, mitochondrial Mg 2+ ATPase from fish brain was quite sensitive. Enzyme inhibition effects of other compounds related to DDT were somewhat less as determined from I 50 and I 70 values. The order of effectiveness in vitro following DDT was TDE, Perthane, methoxychlor and DDE.

Chlorinated hydrocarbon insecticide inhibition of cockroach and honey bee ATPases

Abstract The specific activities and insecticide inhibitions have been studied on Na + K + ATPase and Mg + ATPase differentiated and isolated from nerve cord and muscle tissue of the American cockroach and brain from worker honey bees. Specific activity in the bee brain is believed to be the highest recorded value for such a preparation. Inhibitory effects of p,p′-DDT,p,p′-TDE were highest on Mg ++ ATPase and higher in muscle than in nerve cord. The metabolite, p,p′-DDE had about half the inhibitory effect of p,p′-DDT; p,p′-DDA gave no measurable effect on Mg ++ ATPase but did inhibit Na + K + ATPase. The greatest inhibition at concentrations used, was by dicofol (Kelthane), an acaricide, which gave nearly complete inhibition of Na + K + ATPase, but was not as effective on Mg ++ ATPase. Chlordane inhibited Na + K + ATPase of nerve cord to a greater extent than muscle, whereas the greatest effect of lindane was on Na + K + ATPase of the roach nerve cord and in bee brain. There were considerable differences in magnitude of inhibition and in the type of ATPase inhibition by the different insecticides acting on the different tissues.

DDT: Effect of continuous exposure on atpase activity in fish,Pimephales promelas

Fat head minnows, 45-days old, were continuously exposed to DDT using continuous water flow and constant temperature conditions. Exposures were to 0.5 and 2.0 ppb of DDT in water, and combinations of the two concentrations with 50 ppm in food, and 50 ppm in food alone, using C14-DDT in food. Brain homogenates were analyzed for enzyme activity from fish treated for 56, 118, 225, and 266 days; and gill analysis was made at 225 and 226 days exposure. Enzyme reductions were greatest in oligomycin-sensitive (mitochondrial) Mg2+ ATPase, with pronounced effects (over 50% inhibition) at the 266th sampling day. In contrast, Na+-K+ ATPase and oligomycin-insensitive Mg2+ ATPase activities were activated by as much as 28% and 40%, respectively. Mitochondrial Mg2+ ATPase of fish brain has been inhibited to the greatest extent in previously reportedin vitro studies. All three ATPase enzymes were reduced in gill tissue sampled at the 266th day, with mitochondrial Mg2+ ATPase showing the greatest decline.

Inhibition of oligomycin-sensitive and -insensitive magnesium adenosine triphosphatase activity in fish by polychlorinated biphenyls☆☆☆

Abstract Tests in vitro with four polychlorinated biphenyls (PCBs) on four tissues of fish showed prominent inhibitory effects on oligomycin-insensitive Mg 2+ ATPase, with muscle homogenate being most sensitive. Aroclors 1242 and 1254, in the intermediate range of chlorination, were more effective than 1221 and 1268. Mg 2+ ATPase from mitochondria was not as sensitive to the PCBs when compared with DDT-type compounds which were more effective on mitochondrial Mg 2+ ATPase than on oligomycin-insensitive Mg 2+ ATPase. Some stimulation of Mg 2+ ATPase was evident from the poorest inhibitors, Aroclors 1221 and 1268. Na + −K + ATPase from fish brain homogenate was inhibited by Aroclor 1242 but the dose required was several times that for Mg 2+ ATPase.

Inhibition of spider mite ATPases by plictran and three organochlorine acaricides.

Abstract The ATPase enzyme system from two-spotted spider mites, Tetranychus urticae (Koch) was sensitive, in vitro, to four acaricides. Tricyclohexylhydroxytin (PlictranR) was an outstanding inhibitor of oligomycin-sensitive (mitochondrial) Mg2+ATPase from fish brain and spider mite homogenates. The I50 values were 6.6×10−11M and 6.2×10−10M, respectively. Less effective were chlorbenside, chlorfenethol and ovotran. Plictran at a higher concentration (2×10−7M) was also more effective on Na+-K+ATPase both in mites and fish brain homogenates as compared to chlorfenethol, chlorbenside and ovotran. Plictran inhibited oligomycin-insensitive Mg2+ATPase at concentrations of 10−8M but stimulated at high concentrations (5×10−6M and higher).

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

Abstract Oligomycin-sensitive (O-S) Mg 2+ 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 Mg 2+ ATPase. The negative temperature effect by DDT and analogs on O-S Mg 2+ 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.

The in vivo sensitivity of ATPases to DDT, DDE, and physical immobilization in American cockroaches

Abstract American cockroaches injected with sublethal doses of DDT (0.75 μg/roach) at 5-day intervals showed a 40% reduction in oligomycin-sensitive Mg 2+ ATPase from muscle homogenates, and a 23% reduction of Na + -K + ATPase from nerve cords. Thus, the maximum effect measured occurred with the same enzyme and tissue as determined from in vitro studies. The metabolite, DDE, used at 15 μg per roach, gave no significant change in activity of the ATPase system following injection. In contrast, high single doses of DDT (7.5 μg/roach) and 100 μg DDE and dicofol per roach caused over 30% increase in oligomycin-sensitive Mg 2+ ATPase of muscle and a 10–15% increase in Na + -K + ATPase of nerve cords measured 24 and 48 hr later. While a similar response was observed for Mg 2+ ATPase activities in cockroaches that were immobilized, the increase in enzyme activities were much greater than that caused by the pesticides.

The effect of three pyrethroids on ATPases of insects and fish

Abstract 1. 1. Mitochondrial Mg 2+ ATPase from nervous tissue of cockroaches and fish tissues was the most sensitive to 3 pyrethroids, with Dimethrin and Resmethrin giving 50 per cent inhibition with 20 μmoles or less. Bioethanomethrin was least effective. 2. 2. Na + K + ATPase was less sensitive than mitochondrial Mg 2+ ATPase. Muscle ATPases were inhibited less than ATPases from nervous tissue. 3. 3. Oligomycin-insensitive Mg 2+ ATPase was not affected by any of the pyrethroids tested. 4. 4. A possible relationship between the knockdown effect and inhibition of ATPase by the pyrethroids is discussed.