Estrogenic activity of heavy oil and its assay method

The authors hare proposed a new in vitro assay method for estrogenicity. Th e cellular progesterone receptor (PgR) level in the human breast cancer cel l line MCF-T was measured because PgR has been known to be upregulated by 1 7 beta-estradiol (En). The cellular PgR level was measured by a western blo tting technique. While an E-2 treatment increased the PgR level, tamoxyfen, a typical E-2 antagonist decreased the PgR level elevated by the E-2 treat ment. These results revealed that the cellular PgR level is a good indicati on to evaluate the estrogenicity. Next, the estrogenic activities of Nakhod ka heavy oil and a commercial C-heavy oil were examined. Heavy oil crude ex tracts prepared with ethanol were subjected to the assay. While the extract s increased the PgR level under the E-2-free condition, the extracts decrea sed the PgR level elevated by the E-2 treatment. These results indicate tha t the heavy oil contains compounds which show weak estrogenic activity and act as E-2 antagonists. Dead cells were observed after the oil extract trea tment, and their number increased with an increase of oil extract concentra tion in the cell-culture medium. Environmental samples such as oil-extract, river water, and air particulate extract comprise a wide variety; of compo unds, and are thought to have a cell-killing effect. A cellular PgR express ion method is considered to be more appropriate for assessing the estrogeni c activities of environmental samples, compared with the existing assay met hods, such as the cell-proliferation method (E-Screen assay) and the report er-gene methods.