Effect of pyrethroid‐based liquid mosquito repellent inhalation on the blood–brain barrier function and oxidative damage in selected organs of developing rats

Pesticides have been implicated in various neurological disorders in humans and experimental animals. Our earlier studies have demonstrated a high vulnerability of developing blood–brain barrier (BBB) towards very low level exposure of quinalphos, cypermethrin and lindane. Earlier it has been observed that a cypermethrin‐induced increase in the BBB permeability of neonatal rats was found to be persistent, requiring a longer period of withdrawal for complete recovery. These observations lead us to investigate the effect of a commonly available liquid mosquito repellent (MR) containing a pyrethroid compound, allethrin (3.6% w/v), on the functional integrity of the developing BBB and on certain parameters of oxidative damage in brain, liver and kidney. Two‐day‐old rat pups were allowed to inhale the MR (18 h per day) for 8 days (postnatal days (PND) 2–9). Rats exposed to MR were further withdrawn from the exposure for 8 days (PND 10–17) to study whether the changes induced following inhalation are reversible. Results of the study have shown a significant increase in the BBB permeability (45%) of the MR‐exposed rat pups to a micromolecular tracer, sodium fluorescein (mol. wt. 376), used for the quantitative assessment of the BBB permeability, suggesting a delayed maturity of the BBB system. Brain glutathione (GSH) levels were also decreased (17%) in the exposed individuals. The oxidatively damaged end‐products of lipids, measured as lipid hydroperoxides and conjugated dienes, were found to be increased in brain (42%, 16%), liver (34%, 20%) and kidney (68%, 29%), respectively. The oxidative product of protein, measured as protein carbonyls, was also increased significantly in liver (43%) and kidney (16%) of the MR‐exposed rat pups as compared to age‐matched controls. The biochemical changes that occurred in the BBB permeability and the oxidatively damaged end‐products following MR inhalation in neonatal rats were, however, found to be completely recovered except for an increase in brain GSH (28%) level. The results suggest the possibility of health risk due to exposure to pesticide‐based mosquito repellents, especially when exposure takes place in individuals at an early age. Copyright © 1998 John Wiley & Sons, Ltd.