Different biotransformation of morphine in isolated liver cells from guinea pig and rat.
The biotransformation of morphine was characterized in freshly isolated parenchymal and non-parenchymal liver cells from rats and guinea pigs in suspension culture to establish an in vitro model for morphine metabolism. Liver cells were prepared by a collagenase perfusion technique, and separated by differential centrifugation. Morphine metabolism was investigated at different concentrations (1, 5, 100 and 200 microM). Samples were taken repeatedly during 2-4 hr of incubation, and subsequently analysed on a HPLC system employing both UV and electrochemical detection. In suspensions of hepatocytes from both animal species morphine-3-glucuronide (M3G) was the major metabolite of morphine, and was formed at comparable rates at all concentrations examined. Guinea pig hepatocytes in addition produced considerable quantities of morphine-6-glucuronide (M6G), whereas this metabolite was detected only intracellularly in minor quantities in rat hepatocytes. The ratio between the two morphine glucuronides (M3G/M6G) in suspensions of guinea pig hepatocytes was approximately 4:1. N-Demethylation of morphine was more pronounced per mg cell protein in rat hepatocytes compared to guinea pig cells. Metabolic activity towards morphine was not detected in non-parenchymal cells of the two species. The morphine glucuronidation pattern found in guinea pig hepatocytes resembles to a greater extent than that found in rat hepatocytes the pattern found in in vivo studies of humans. It was concluded that isolated guinea pig parenchymal cells appeared to be a promising in vitro system for studies of morphine glucuronidation, and to observe metabolism in general.
Aasmundstad
T A
TA
National Institute of Forensic Toxicology, Oslo, Norway.
Ripel
A
A
Bodd
E
E
Bjørneboe
A
A
Mørland
J
J
D000818:Animals; D001711:Biotransformation; D002478:Cells, Cultured; D005965:Glucuronates / Q000378:metabolism; D006168:Guinea Pigs; D008099:Liver / Q000378:metabolism*; D008297:Male; D009020:Morphine / Q000378:metabolism*; D009022:Morphine Derivatives / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D005965:Glucuronates; D009022:Morphine Derivatives; D009020:Morphine; C010616:normorphine