Distribution and inhibition of esterases in various body tissues of susceptible and resistant German cockroaches (Dictyoptera : Blattellidae)

The distribution and inhibition of esterase activity among body of the resi stant Crawford and susceptible CSMA strains of male German cockroach, Blatt ella germanica (L.), were evaluated with alpha- and beta-naphthyl esters us ing a spectrophotometric assay and native polyacrylamide gel electrophoresi s. The esterase activities in the Crawford strain were significantly higher than in the CSMA strain in most tissues except midgut and male genitalia, where the activities were similar. In both strains, isozyme a was dominant in the brain and fat body and isozymes c and d were more abundant in the mi dgut; but in addition to isozyme a, isozyme b was observed only in the Craw ford strain. The alpha-naphthyl butyrate (alpha-NB) and beta-naphthyl aceta te (beta-NA) esterase activities in the brain of both strains were complete ly inhibited by most inhibitors (DEF, 3,4-dichloroisocoumarine, paraoxon, p epstatin A, and propoxur). However, in the midgut tissue and contents, the activities and inhibition patterns of the alpha-NB and beta-NA esterase wer e apparently different from the brain and between strains. The complete inh ibition by paraoxon was observed regardless of the strain, substrate type, and body part for enzyme source. In esterase inhibition on native PAGE gels , paraoxon completely inhibited the activity of most esterases similar to t he results from spectrophotometric assay. In addition, the esterase b was o bserved from the whole body homogenates of several German cockroach resista nt strains on native PAGE analysis.