pression.

Moreover, E2 and PH induced ERα expression mainly in the hepatocytes located in the periportal area ([Figure 4B](#f4-ceg-8-175){ref-type="fig"}), and these hepatocytes are known to actively proliferate after PH.[@b38-ceg-8-175]

Delayed hepatocyte proliferation after PH in OVX mice
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No significant differences in liver weight were observed between the OVX and control mice before or after PH ([Figure 5A and B](#f5-ceg-8-175){ref-type="fig"}). Hepatocytes are the main parenchymal cells of the liver, and DNA from the recovered livers was extracted and analyzed. The liver DNA quantities were restored by 4 days after PH in the OVX and control mice, and no significant differences were observed between the OVX and control mice ([Figure 5C](#f5-ceg-8-175){ref-type="fig"}); these findings indicate that OVX had no significant effect on the liver regeneration. Moreover, hepatocyte proliferation following PH was analyzed based on BrdU incorporation. The rate of hepatocyte proliferation in the control mice was significantly elevated 36--44 hours after PH, but that of the OVX mice was significantly higher at 52 hours, and 60--72 hours after PH ([Figure 5D](#f5-ceg-8-175){ref-type="fig"}). These data indicate that the OVX mice displayed slightly delayed hepatocyte proliferation ([Figure 5D](#f5-ceg-8-175){ref-type="fig"}) but no significant change in liver weight/DNA amount recovery ([Figure 5B and C](#f5-ceg-8-175){ref-type="fig"}).

Discussion
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PH induced increases in E2 concentrations in ORC and OVX living organisms
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This is the first study that PH induced E2 production in ORC and OVX animals. In the papers in the 1970s and 1980s, and in our latest studies, no observation of E2 induction in ORC/OVX rodents or human beings was reported.

E2 administration and PH induced ERα expression in the livers of the female mice
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