Enhanced metabolism of morphine in Octodon degus compared to Wistar rats

Comparative studies of the actions of morphine in different mammals have shown that Octodon degus presents an unusual tolerance to this compound. Morphine glucuronidation and N-demethylation in microsomal fractions of Octodon degus were 10.9 and 50.0 nmol of product formed/min/g of wet liver, respectively. In Wistar rat these activities were 10.5 and 12.5, respectively. Microsomal protein and cytochrome P-450 contents were two and four times higher in Octodon degus than in the Wistar rat, respectively. These results may explain the high tolerance to morphine presented by Octodon degus.