Methoprene metabolism

Reports are published on the metabolism of methoprene by plants (25), aquatic microorganisms (26), soil microbes (27), house flies and mosquitoes in vivo (28), resistant house flies in vivo and in vitro (29), a steer (30), a lactating cow (31), chickens (32), and bluegill fish (33). In addition, radioactive material balance studies have been published for a guinea pig, steer, and cow (34), chickens (35), and rats (36, 37), including whole-body autoradiography in rats (37). 

Metabolism studies of methoprene in nonaquatic organisms have provided background data which must be considered prior to discussing the fate of methoprene in aquatic systems. All nonaquatic metabolic studies reported to date have utilized [5-1 C]methoprene. The location of radiocarbon was selected both for ease of synthesis and for anticipated metabolic stability. However, studies in plants and bovines (25, 30, 31) revealed many presumed "metabolites" to be radiolabeled natural products, or "nonmetabolite residues". Primary metabolites of methoprene resulting from ester cleavage and/or (O-demethylation have been... 

Figure 5. Metabolism of methoprene by soil and aquatic microorganism (26, 27)...

At this point the history of the concept of hormonal control of insects should be recalled, since the major reasons for the selection of JH as a rational lead for pesticide design were the beliefs that JH occurred only in insects and not in other animals. The implication was that JH would therefore be selectively active in insects with no significant effects on other forms of life. In the cases of JH analogs of the farnesane skeleton, extensive studies of comparative toxicology have largely verified these beliefs. Toxicological results have been reviewed in detail (20 ) and a comprehensive study of the environmental fate and metabolism of methoprene has been completed (2 1). ... 

Methoprene degrades rapidly in sunlight, both in water and on inert surfaces. It is metabolized rapidly in soil under both aerobic and anaerobic conditions (half-life =10-14 days). The major microbial degradation product is carbon dioxide. Degradation in both freshwater and saltwater is also quite rapid with a half-life of 10-35 days at 20°C. Methoprene is not very soluble in water (< 2 ppm) and as a result is not... 

The activity of methoprene against T. mnlunr has been shown to be increased by the addition of PBO (Solomon et al., 1973). Resistant . aixtanvttm adults have been found to metabolize PBO and juvenile hormone mimics more quickly than susceptible strains by attacking the methylene group (Rowlands and Dyte, 1979) The larvae were more resistant to both the hormone mimic and high levels of PBO. 

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