Sexual maturation inhibition using exemestane and tamoxifen in female olive flounder (Paralichthys olivaceous)

Abstract

Sex determination in some reptiles, amphibians, and fishes is influenced by environmental factors. Exemestane acts as an estrogen agonist non-steroid hormone. Olive flounder (Paralichthys olivaceous) is easily affected by water temperature or sex steroid hormone treatment during sex determination. Tamoxifen is widely used as a drug in human cancer therapy as an anti-estrogen agent (estrogen receptor antagonist). In this study, we intraperitoneally injected exemestane and tamoxifen, a pre-maturation sex hormone inhibitor, into the bodies of female olive flounder. In both cases, the expression of estrogen receptor mRNA and vitellogenin mRNA in the liver was almost identical. In the case of exemestane injection, intersex was confirmed histologically, but it was not confirmed in tamoxifen. Although these results suggest the possibility of the synthesis of estrogen by tamoxifen, the underlying mechanism has not yet been fully investigated. Hence, examinations are needed to confirm the direct involvement of tamoxifen.