Title: Mechanisms of action of phytosterols on goldfish (Carassius auratus) gonadal steroidogenesis.
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Abstract: beta-Sitosterol, a phytosterol found in high concentrations in pulp mill effluents, has been proposed as one of the causative agents for the steroid depressions and reproductive dysfunctions observed in fish exposed to pulp mill effluents. In this study, goldfish (Carassius auratus) were exposed to a mixture of phytosterols rich in beta-sitosterol to determine its effects on gonad steroidogenesis. In the first series of experiments, beta-sitosterol (75% pure) (150 mug/g, silastic pellet implants) caused significant depressions in the steroidogenic pathway downstream of pregnenolone in both male and female goldfish. The second series of experiments confirmed previous work in brook trout (Salvelinus fontinalis) demonstrating a mixture of phytosterols rich in beta-sitosterol (55%) does not affect the ability of cytochrome P450scc to convert cholesterol to pregnenolone in male goldfish. In the final set of experiments, phytosterols (150 mug/g, silastic pellet implants, 55% beta-sitosterol) and beta-sitosterol (95% pure) decreased the reactive pool of cholesterol in male goldfish, indicating that beta-sitosterol (and other phytosterols) may be affecting the rate of cholesterol transfer across the mitochondrial membrane. These results support the hypothesis that beta-sitosterol’s key effects on plasma steroid depression are via the steroidogenic pathway.
Keywords: beta-sitosterol, mitochondria, phytosterol, reactive pool of cholesterol, StAR.
Collaborators on this project:
- Dr Deborah MacLatchy, University of New Brunswick, Saint John, NB, Canada (MSc supervisor)
- Miss Christine Gilman, University of New Brunswick, Saint John, NB, Canada
- Mr Wayne Armstrong, University of New Brunswick, Saint John, NB, Canada
- Dr Tillman Benfey, University of New Brunswick, Fredericton, NB, Canada
- Dr Thierry Chopin, University of New Brunswick, Saint John, NB, Canada
- Dr Kelly Munkittrick, University of New Brunswick, Saint John, NB, Canada
Peer-reviewed publications from this project:
- Leusch FDL, and MacLatchy DL. 2003. Implants of beta-sitosterol impede cholesterol transfer across gonadal mitochondrial membranes isolated from male goldfish (Carassius auratus). Gen. Comp. Endocrinol. 134:255-263.
- Gilman CL, Leusch FDL, Breckendridge WC, and MacLatchy DL. 2003. Effects of a phytosterol mixture on male fish plasma lipoprotein fractions and P450scc activity. Gen. Comp. Endocrinol. 130:172-184.