Porphyric Insecticides

Abstract

The destructive photodynamic properties of δ -aminolevulinic acid-induced protoporphyrin IX accumulation has been well documented in insect and animal tissues. In this work the responses of isolated organs and tissues of several insect species to Proto accumulation were investigated. In Trichoplusia ni, and Helioverpa (Heliothis) zea, significant amounts of Proto accumulated in the midgut, and fat bodies. In Blattella germanica (German cockroach), more of the Proto accumulated in the male and female guts than in the abdomen. Anthonomus grandis (Cotton boll weevil) abdomens accumulated less Proto than the other three species. Oxygen consumption in T. ni midguts enriched in Proto was monitored before and after exposure to 2-hr of illumination. Decrease in O2 consumption suggested photodynamic damage. To determine the physiological basis of this phenomenon, the subcellular site of protoporphyrin IX accumulation and singlet oxygen generation were investigated. Protoporphyrin IX accumulation occurred mainly in the mitochondria. The accumulated protoporphyrin resulted in the formation of singlet oxygen. ALA + Oph treatment exhibited deleterious effects on mitochondrial activities before illumination, which tended to obscure the possible involvement of singlet oxygen in enzyme Photoinactivation. However, the rate of NADH cytochrome c reductase activity, appeared to decline more rapidly in the light, in protoporphyrin IX-enriched than in control mitochondria. This in turn suggests the possible involvement of singlet oxygen in the enhanced inactivation of mitochondrial cytochrome c reductase activity by light.