Effect of a PCB-based transformer oil on testicular steroidogenesis and xenobiotic-metabolizing enzymes.

Pyralene is a PCB-based transformer oil with a unique PCB congener profile when compared to other mixtures. We studied the influence of Pyralene on testicular steroidogenesis and the status of xenobiotic-metabolizing enzymes in the testis and liver of rats during oral exposure (10 and 50 mg/kg body weight, p.o. daily for 1 week) and a 3-week post-treatment recovery period. As expected, Pyralene induced a rapid and sustained increase in mRNA transcripts for CYP1A1 and CYP2B1 in hepatocytes that was associated with a dramatic increase in ethoxyresorufin-O-deethylase (EROD) and pentoxyresorufin-O-deethylase (PROD) activities. Testicular androgenesis and the conversion of progesterone to testosterone in testicular microsomes were bidirectionally affected. An increase in these parameters was observed 24h after the initial administration of Pyralene, followed by inhibition that lasted until the fourth post-treatment day. Expression PCR analysis revealed a significant decrease in 17beta-hydroxysteroid dehydrogenase (17betaHSD) transcript abundance at 48 h after Pyralene administration. In contrast, transcripts for several other steroidogenic enzymes and for testicular CYP1A1, CYP1B1, and CYP2B1 were unaffected under the same conditions. These results in the rat indicate that a sub-chronic exposure to Pyralene disrupted testicular steroidogenesis and suggest the mechanism may involve direct action on the regulation of specific steroidogenic enzymes such as 17betaHSD.