Insect Inhibitors of Drug Oxidation Enzymes

Abstract

The problem was to find out why housefly microsomal preparations do not possess drug oxidation activity when preparations from vertebrate liver are active. There are a number of reports that insects contain enzymes capable of exidising insecticides - see reviews by Smith (1962) 138, Perry (1964) 106, and Winteringham (1965) 157. A comparative study of Sevin (1-naphthyl N-hydroxymethyl-carbamate) metabolism by rat liver microsomes, goat, cockroaches, houseflies, bean and cotton plants has also appeared43,42. There is little doubt that insects can oxidise alkyl side chains of aromatic compounds, Kelthane production from DDT3 and p-nitrobenzoic acid from p-nitrotoluene24 are examples. Chakratorty and Smith24 found that oxidation of p-nitrotoluene occurred in intact, isolated tissues of the locust (Schistocerca) in saline i.e. fat-body, gastric cecae (which, together contained most of the activity) foregut, midgut, hindgut,malpighian tubules. However, homogenisation of any of the tissues gave an inactive preparation. Thus, here, the inactivity is an artifact of homogenisation. An active preparation was obtained from the inactive fat-body homogenate by centrifugation at 10,000g for 10 minutes in 0.25 M sucrose.