Interaction of pyrethroids with ion transport pathways present in frog skin

Abstract

Abstract-We measured the ability of deltamethrin and permethrin to stimulate the ion transport operated by the frog skin. Ion transport was monitored by measuring the short-circuit current. Deltamethrin and permethrin, added to the fluid bathing the internal surface of the isolated frog skin, showed a seasonal feature and were more effective in increasing short-circuit current in the period between June and October. Transepithelial influxes and outfluxes of 22 Na ϩ and 36 Cl Ϫ across symmetrical parts of the short-circuited skin were then measured. Deltamethrin was found to increase net Na ϩ absorption and, to a lesser extent, Cl Ϫ secretion. The presence of a Cl Ϫ secretory mechanism is supported by two observations, those being that the short-circuit current value, recorded when deltamethrin and amiloride (inhibitor of Na ϩ channels) were simultaneously present, was higher than that obtained in the presence of amiloride alone and that bumetanide, a classic inhibitor of Cl Ϫ secretion, completely inhibited the component of the Cl Ϫ outflux that was induced by the deltamethrin stimulation. The stimulations of short-circuit current respectively caused by deltamethrin (type II pyrethroid) and permethrin (type I) were comparable and similarly affected by indomethacin (an inhibitor of cyclooxygenase) and W7 (an inhibitor of the Ca 2ϩ /calmodulin system). These findings suggest that, in frog skin, the cellular mechanism of action of type I and type II pyrethroids is similar.

Pyrethroid stimulation of ion transport across frog skin

“…In a previous article, we showed that deltamethrin (type II) is more active than permethrin (type I) in stimulating the Na ϩ absorption and, to a lesser extent, the Cl Ϫ secretion operated by the frog skin [12]. In this article, we extend our study to eight pyrethroids in order, first, to reach the conclusion that pyrethroids, as a family of compounds, stimulate ion transport and, second, to investigate the mechanism of stimulation.…”

“…In a previous article, we showed that deltamethrin and permethrin, added to the fluid bathing the internal surface of isolated frog skin, increase the ion transport operated by the frog skin [12]. The increase caused by deltamethrin and permethrin in the period between June and October is much higher than in the rest of the year.…”

“…Values are mean Ϯ standard errors from9,9,9,12,10, 30,7, and 8 experiments, respectively. Values are mean Ϯ standard errors from9,9,9,12,10, 30,7, and 8 experiments, respectively.…”

Atrazine increases the sodium absorption in frog (Rana esculenta) skin

“…Alternatively, atrazine could decrease the transepithelial resistance of the skin by increasing the activity of the ion‐transport pathways operating in frog skin. This is the case, for example, with the synthetic pyrethroid deltamethrin, which stimulates the short‐circuit current as a result of increases in Na + absorption and, to a lesser extent, Cl − secretion in R. esculenta skin [14]. The following experiments were then performed to verify the role of Na + and Cl − pathways in response to atrazine challenge.…”

“…Therefore, isolated frog skin has been used as a model for studying the effects of pesticides on epithelial ion transport [12,13]. In previous studies, we have shown that the ion transport operated by the frog ( Rana esculenta ) skin is increased by 1 mM carbaryl [13] and 5 μM pyrethroids [14,15]. In the present study, we have extended our investigation to atrazine and five of its derivatives.…”