Activation of Guthion by Tissue Preparations From the American Cockroach1

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Abstract
Activation of Guthion® (O,O-dimethyl S-(4-oxo-1,2,3-benzotriazin-3-(4H)-ylmethyl) phosphorodithioate) and degradation of its active metabolite and P(O)S Guthion by whole tissues and tissue homogenates of the adult, female American cockroach, Periplaneta americana (L.), were estimated manometrically by inhibition of house fly (Musca domestica L.) head cholinesterase. A Guthion-activating enzyme system is present in several tissues of the American cockroach. The most active whole tissues, in descending order, were: Malpighian tubules, fat body, heart, nerve cord, ovaries and caeca. The fat body probably has the greatest capacity for anticholinesterase production per insect. Because P(O)S Guthion and the active metabolite of Guthion were degraded by tissue homogenates, the activation of Guthion by tissue homogenates was studied by blocking degradation of the active metabolite with 0.01 M sodium fluoride. Under these conditions, homogenates of the midgut and caeca were most active, followed by Malpighian tubules, fat body, foregut, and hindgut. Activation with homogenates required oxygen and NADPH2 or other nicotinamide nucleotides as cofactors.