Estrogenic activity of procymidone in rainbow trout ( Oncorhynchus mykiss) hepatocytes: a possible mechanism of action

Abstract

It is known that procymidone modifies sexual differentiation in vivo and in vitro, and that it induces vitellogenin (Vtg) synthesis in primary cultured rainbow trout hepatocytes. The aim of this study was to evaluate the mechanism underlying this latter in vitro estrogenic action. The cells were treated for 24 h with procymidone 150 μM (with 17β-estradiol [E2] 20 μM as a positive control) combined with an estrogen receptor (ER) antagonist (tamoxifen 20 μM or ICI 182,780 1 μM) or, given the drug toxic action on the production of reactive oxygen species (ROS), a free radical scavenger (α-tocopherol 30 μM). The results from ELISA experiments provided evidence that procymidone Vtg-induction is inhibited by ER antagonists and by α-tocopherol suggesting that both ER and ROS are involved in this effect. The ROS detection revealed that the treatment with α-tocopherol and tamoxifen completely prevented ROS induction by procymidone, that was not inhibited by ICI 182,780. In exploring the mechanism mediating these events and its timing, we found that procymidone induced mitogen-activated protein kinase (MAPK) at 30 and 60 min, and that this effect was blocked by co-treatment with α-tocopherol. In summary, the results of the study clearly support the idea that the estrogenic activity of procymidone in primary cultured trout hepatocytes is mediated by ROS production, and that this activity is similar to that of the ligand-independent ER activation involving MAPK.