The Effects of Insecticides on Cytochrome Oxidase Obtained from the American Cockroach1

Abstract

The effect of 26 insecticidal compounds upon cytochrome c oxidase obtained from the coxal muscle of the American cockroach was ascertained by a manometric method, using phosphate buffer in the enzyme digest. Under these conditions, all the chlorinated hydrocarbons tested completely inhibited the cytochrome c oxidase of the muscle at 10-3 [image] concentrations (concn.), and caused a slight transient stimulation at 10-5 [image]. The inhibition at the higher concn. was rapid with DDD, methoxychlor, lindane and toxaphene, but slow in onset with DDT, aldrin, dieldrin and the chlordan compounds. The dinitro compounds DNOC, DNCHP and DNBP were stimulatory at the lower concns., the 2 latter compounds inhibiting at the higher concn. The organic phosphates, especially TEPP, stimulated at one or both concns., only parathion and malathion completely inhibiting at 10-3 [image]. Nicotine stimulated at both concns. and rotenone at 10-5 [image] only, while the pyrethrins and allethrin completely inhibited cytochrome oxidase at the higher concn. At 10-3 [image], phenothiazine, Lethane 60 and Lethane 384 markedly inhibited cytochrome oxidase.