In vivo implants of β-sitosterol cause reductions of reactive cholesterol pools in mitochondria isolated from gonads of male goldfish (Carassius auratus)
Author(s)
Leusch, FDL
MacLatchy, DL
Griffith University Author(s)
Year published
2003
Metadata
Show full item recordAbstract
߭Sitosterol, a phytosterol found in high concentrations in pulp mill effluents, has been proposed as one of the causative agents for steroid depressions observed in fish exposed to pulp mill effluents. Previous studies have suggested a cholesterol-mediated mechanism; however, it is unknown how ߭sitosterol depresses gonadal steroidogenesis. In this study, adult male goldfish (Carassius auratus) were exposed for 24-31 days to ߭sitosterol (55% of a phytosterol mixture or 96% pure; 150 lg/g; Silastic implant) after which gonadal mitochondria were isolated. Pregnenolone production, an indicator of the size of the pool of ...
View more >߭Sitosterol, a phytosterol found in high concentrations in pulp mill effluents, has been proposed as one of the causative agents for steroid depressions observed in fish exposed to pulp mill effluents. Previous studies have suggested a cholesterol-mediated mechanism; however, it is unknown how ߭sitosterol depresses gonadal steroidogenesis. In this study, adult male goldfish (Carassius auratus) were exposed for 24-31 days to ߭sitosterol (55% of a phytosterol mixture or 96% pure; 150 lg/g; Silastic implant) after which gonadal mitochondria were isolated. Pregnenolone production, an indicator of the size of the pool of reactive cholesterol, was then measured in the isolated mitochondria. Sterol exposure did not affect P450 side-chain cleavage enzyme (converts cholesterol to pregnenolone) activity but did decrease the size of the mitochondrial pool of reactive cholesterol, suggesting ߭sitosterol is impeding cholesterol transfer across the mitochondrial membrane. This finding is supported by the observation that 25-hydroxycholesterol, which passes through mitochondrial membranes without need for a membrane transporter, restores ߭sitosterol-induced reductions in pregnenolone production.
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View more >߭Sitosterol, a phytosterol found in high concentrations in pulp mill effluents, has been proposed as one of the causative agents for steroid depressions observed in fish exposed to pulp mill effluents. Previous studies have suggested a cholesterol-mediated mechanism; however, it is unknown how ߭sitosterol depresses gonadal steroidogenesis. In this study, adult male goldfish (Carassius auratus) were exposed for 24-31 days to ߭sitosterol (55% of a phytosterol mixture or 96% pure; 150 lg/g; Silastic implant) after which gonadal mitochondria were isolated. Pregnenolone production, an indicator of the size of the pool of reactive cholesterol, was then measured in the isolated mitochondria. Sterol exposure did not affect P450 side-chain cleavage enzyme (converts cholesterol to pregnenolone) activity but did decrease the size of the mitochondrial pool of reactive cholesterol, suggesting ߭sitosterol is impeding cholesterol transfer across the mitochondrial membrane. This finding is supported by the observation that 25-hydroxycholesterol, which passes through mitochondrial membranes without need for a membrane transporter, restores ߭sitosterol-induced reductions in pregnenolone production.
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Journal Title
General and Comparative Endocrinology
Volume
134
Issue
3
Subject
Zoology
Veterinary sciences
Clinical sciences not elsewhere classified