Pharmacokinetics of dieldrin with special reference to its metabolism in the epicuticular wax layer in Calliphora erythrocephala

Abstract

1. A part of the topically applied [ 14C]dieldrin was degraded in the epicuticular wax layer of adult blowflies, Calliphora erythrocephala. At 24 hr after the treatment, the ratio of unchanged dieldrin to total metabolized dieldrin in the epicuticular wax layer was approx 2:3 while the ratio inside the body was found to be nearly 19:1. 2. Qualitatively, the metabolites found in the epicuticular wax layer were different from those detected inside the body. The nature of some of metabolites found in the faeces were, however, similar to those detected in the external extract. 3. Pretreatment with sesamex (10 μg/fly) completely inhibited the internal metabolism of dieldrin, but the number of its metabolites formed in the epicuticule remained unaffected. 4. The external metabolism of dieldrin was absent in the larval stage of C. erythrocephala. The difference in the metabolism of dieldrin between the adult and the larval stages had both a quantitative and a qualitative basis. 5. The penetration of topically applied dieldrin occurred readily in the adult blowflies as compared to larvae. Losses due to volatilization were also higher in the case of adult flies.