| The objective of this research was to characterize the percutaneous absorption of the organophosphorous pesticide, malathion, across the skin of bullfrogs (Rana catesbeiana) and marine toads ( Bufo marinus) using in vitro models. An established mammalian model for percutaneous absorption, the two-compartment Teflon flow-through diffusion cell assay, was adapted to anuran skin to examine species and anatomical site differences in absorption and partitioning of C14-radiolabeled malathion. Malathion absorption was greater across the ventral skin compared to dorsal skin in both bullfrogs and marine toads but did not differ significantly between species. The issue of short-term storage and viability of anuran skin for diffusion cells was examined using glycerol preservation and cryopreservation techniques. Bullfrog skin viability was retained for 28 days, while marine toad skin viability significantly decreased after 7--10 days. A novel in vitro model, the harvested perfused anuran limb (HPAPL) preparation, which maintained an intact microvasculature to the skin, was developed. The HPAPL represented an improvement over diffusion cells by retaining the anatomic and physiologic integrity of the skin. Doppler ultrasound was used to determine the perfusion rate for the HPAPL by measuring the physiologic blood flow of the pelvic limb in vivo. In addition to the characterization of the percutaneous absorption of malation in anurans, effects of sublethal doses on brain acetyl cholinesterase activity in bullfrogs and marine toads, were examined using a modified Ellman spectrophotometric technique. Sensitivity to environmental toxins make anurans potentially important animal models for studying the impacts of organophosphorous insecticide contamination of the environment. |
