ATRAZINE INCREASES THE SODIUM ABSORPTION IN FROG (RANA ESCULENTA) SKIN

摘要

The presence of atrazine in agricultural sites has been linked to the decline in amphibian populations. The efforts of the scientific community generally are directed toward investigating the long-term effect of atrazine on complex functions (reproduction or respiration), but in the present study, we investigated the short-term effect on the short-circuit current (I_(SC)), a quantitative measure of the ion transport operated by frog (Rana esculenta) skin. Treatment with 5 μM atrazine (1.08 mg/L) does not affect the transepithelial outfluxes of [~(14)C]mannitol or [~(14)C]urea; therefore, atrazine does not damage the barrier properties of frog skin. Atrazine causes a dose-dependent increase in the short-circuit current, with a minimum of 4.64 ±0.76 μA/cm~2 (11.05% ± 1.22%) and a maximum of 12.7 ± 0.7 μA/cm~2 (35% ± 2.4%) measured at 10 nM and 5 μM, respectively. An increase in I_(SC) also is caused by 5 μM ametryne, prometryn, simazine, terbuthylazine, or terbutryn (other atrazine derivatives). In particular, atrazine increases the transepithelial ~(22)Na~+ influx without affecting the outflux. Finally, stimulation of I_(SC) by atrazine is suppressed by SQ 22536, H89, U73122, 2-aminoethoxydiphenyl borate, and W7 (blockers of adenylate cyclase, protein kinase A, phospholipase C, intracellular Ca~(2+) increase, and calmodulin, respectively), whereas indomethacin and calphostin C (inhibitors of cyclooxygenase and protein kinase C, respectively) have no effect.