Studies on the Percutaneous Absorption of Parathion and Paraoxon: Vi.In Vivo Decomposition of Paraoxon During the Epidermal Passage

Abstract

In five earlier papers of this series various aspects of the percutaneous absorption of the well-known insecticide parathion (E 605, or diethyl 4-nitrophenyl thionophosphate) and its more toxic oxygen analogue paraoxon (E 600, or diethyl 4-nitrophenyl phosphate) were discussed. These studies covered such topics as the in vitro metabolism and enzymic degradation within the skin (8) the distribution of 32P-labelled parathion within the skin (2); the rate of absorption of parathion as investigated with the aid of labelled material and disappearance technic (3); decontamination of human skin from parathion (4); and also the rate of absorption of paraoxon (5). The method used in the last mentioned case was a dose-response technic, i.e. the rate of inhibition of plasma cholinesterase activity was determined following percutaneous absorption and continuous intravenous infusion in two separate groups of cats. The intravenous infusion was adjusted so that the rate of enzyme inhibition in plasma was approximately the same as following topical application. Since the rate of infusion and the area of absorption were known the rate of percutaneous absorption could easily be calculated.