Estrogenicity of phytosterols evaluated in vitro and in vivo.

The estrogenic activity of two phytosterol preparations was evaluated in vitro and in vivo. For the in vitro evaluation, freshly separated hepatocytes of rainbow trout were used. By contrast, the in vivo evaluation was performed by injecting the phytosterols intraperitoneally into juvenile rainbow trout. Both assays confirmed the estrogenic activity of the phytosterols. The in vitro screening technique, based on the synthesis and secretion of vitellogenin from the isolated liver cells, produced a clear, significant curve in response to the presence of both phytosterol mixtures. In the in vivo tests, the phytosterol preparations caused significant increases in plasma vitellogenin concentrations of juvenile fish. These shortterm assays proved to be suitable for assessing the estrogenic activity of phytosterols.