Insecticide chlorinated alicyclic

A drin and Dieldrin Metabolism.— The in vivo metabolism of the chlorinated alicyclic insecticides, aldrin and dieldrin, has been measured. Fish were exposed to l c-labelled aldrin or dieldrin for 6 hours. The metabolism of each compound was monitored by thin layer chromatography of hexane and chloroform-methanol extracts of liver homogenates, followed by liquid scintillation counting of the spots (5,15,16). 

The levels of resistance which the mosquitofish demonstrate toward the chlorinated alicyclic insecticides (40 - 500 fold) are the most intriguing of those studied, yet they are impossible to explain in terms of disposition and biotransformation alone. Although insecticide metabolism cannot be completely discounted, it contributes little to chlorinated alicyclic resistance. 

We have, therefore, been able to indirectly assess the importance of three factors involved in chlorinated alicyclic insecticide resistance in mosquitofish disposition, metabolism and target site sensitivity. In a highly polluted environment in which mosquitofish have been placed under severe selective pressures by chronic exposure to insecticides, the system of metabolism appears to be of little significance in resistance the... 

Hepatic mixed-function oxidase activities demonstrated seasonal trends, with higher specific activities in the cold weather months in both populations with few differences in enzyme activities or cytochrome levels between the two populations. Metabolism of aldrin, dieldrin and DDT was similar between the two populations. R fish have larger relative liver size and, therefore, a greater potential for xenobiotic metabolism. However, biotransformation appears to be of minor importance in chlorinated alicyclic insecticide resistance in mosquitofish barriers to penetration appear to be of greater importance and an implied target site insensitivity appears to be the most important factor in resistance. 

Barriers to insecticide penetration undoubtedly contribute to chlorinated alicyclic resistance. However, we are led to conclude that these extremely high levels of resistance are the result of a postulated insensitivity of the target site which allows these fish to tolerate elevated internal levels of these toxicants. 

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