Introduction: 

We have already shown that several pesticides stimulate the sodium absorption operated by the isolated frog skin. According to the Overton rule, the partition coefficient of organic molecules between two non miscible phases, i.e. octanol and water, is a tool useful to predict the permeability across the cellular membranes.In this investyigation we have verified the dependence of the sodium absorption on the partition coefficient for a panel of pesticides.

Methods: 

The effect of 5 mM atrazine, diuron, paraquat, glyphosate, bioellethrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, permethrin, and prometryne on the sodium absorption operated by the frog (Rana esculenta) skin was estimated by measuring the short-circuit current (Isc) for 1 h. The highest Isc value was used to calculate DIsc (%) which was the mean value of the difference between the maximum increase and the control, normalized on the control value (100%).

Results: 

The DIsc caused by each substance was plotted versus its logKow. The coefficient of determination (R²), obtained by using a linear regression procedure, was good. The lowest and the highest DIsc were 7,1% in the case of glyphosate (logKow -3.4) and 35% in that of deltametrin (logKow 5.4), respectively.

Conclusions: 

Our results demonstrate that the logKow is a valid tool in order to predict the biological activity of xenobiotic molecules which need to cross biological membranes before affecting cellular targets.