SUPEROXIDE FORMATION PRECEDING FLIGHT-MUSCLE HISTOLYSIS IN SOLENOPSIS- FINE-STRUCTURAL CYTOCHEMISTRY AND BIOCHEMISTRY

In Solenopsis spp., muscle histolysis or breakdown is a normal process in females and is initiated in the flight muscles only immediately af ter a mating flight. Information regarding the presence of the oxyradi cal scavenging enzyme superoxide dismutase (SOD) and the formation of the radical oxygen intermediate superoxide (SO) during the early stage s of flight muscle histolysis in this insect was investigated. In norm al fibrillar flight muscles from control animals, SOD was immunolocali zed to vesicular and tubular components of the sarcotubular system. La nthanum tracer studies indicated that some of these SOD-positive struc tures might be tubulovesicles continuous with the extracellular space. Following the injection of virgin alates with experimental haemolymph obtained from artificially inseminated females, the membrane delimite d elements of the sarcotubular system became increasingly swollen and dilated with time (from 60 to 120 minutes postinjection) with a concom itant decrease in SOD activity and an increase in oxyradical formation . Many similar vesicles were lanthanum-positive. SO was not seen in th e sarcoplasmic vesicles and tubules of control insects. The biochemica l quantification of SO release over a 2-hour period showed a marked in crease in oxyradical formation following treatment with the experiment al haemolymph in comparison to control insects. Also, the addition of superoxide dismutase depressed SO formation under these conditions. De spite the histochemical and biochemical changes seen in the muscles of experimental insects, by 2 hours post-treatment there was no evidence of muscle necrosis. From these studies on flight muscle histolysis/ne crosis in Solenopsis it appears that the formation of oxyradicals migh t represent an early event in myopathogenesis and subsequent tissue in volution. The generation of SO is more than likely to be associated wi th alterations in the normal structure, biochemistry and permeability of the biomembranes which delimit the sarcotubular system.