Ki. Ahammadsahib et al., POLYSUBSTRATE MONOOXYGENASES AND OTHER XENOBIOTIC-METABOLIZING ENZYMES IN SUSCEPTIBLE AND RESISTANT COLORADO POTATO BEETLE, Pesticide biochemistry and physiology, 49(1), 1994, pp. 1-12
The activities of key defensive enzymes against xenobiotics were studi
ed in two azinphosmethyl-resistant and one susceptible strain of Color
ado potato beetle (Lepinotarsa decemlineata Say) with emphasis on the
microsomal polysubstrate monooxygenase system. Monooxygenase activity
comparable to that in other coleopterans was observed in the oxidation
of NADPH, O-demethylation of p-nitroanisole, N-demethylation,of amino
pyrine, and epoxidation of aldrin. Aniline hydroxylase activity was no
t detected. Monooxygenase activity against aminopyrine was largely con
fined to the microsomal fraction of homogenates and was more active in
the larval gut than in the fat body. Microsomal NADPH oxidation was i
nhibited strongly in vitro by SKF 525-A and in vivo by prior treatment
of insects with piperonyl butoxide. The activity of the monooxygenase
system was approximately twice as high in the resistant strains as th
at in the susceptible strain. Glutathione transferase activity was als
o elevated in the resistant strains, but no elevation in carboxyestera
se activity was seen. Piperonyl butoxide pretreatment increased the to
xicity of azinphosmethyl several-fold more strongly in the resistant t
han susceptible strain, indicating a significant role for monooxygenas
e activity in resistance. However, in both strains, resistance to azin
phosmethyl is multifactorial and enhanced monooxygenase activity is on
ly one contributing factor. (C) 1994 Academic Press, Inc.