Merck

Morphine glucuronidation increases its analgesic effect in guinea pigs.

Life sciences (2014-06-27)
Ana Oliveira, Dora Pinho, António Albino-Teixeira, Rui Medeiros, Ricardo Jorge Dinis-Oliveira, Félix Carvalho
ABSTRACT

Morphine is extensively metabolized to neurotoxic morphine-3-glucuronide (M3G) and opioid agonist morphine-6-glucuronide (M6G). Due to these different roles, interindividual variability and co-administration of drugs that interfere with metabolism may affect analgesia. The aim of the study was to investigate the repercussions of administration of an inducer (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD) and an inhibitor (ranitidine) of glucuronidation in morphine metabolism and consequent analgesia, using the Guinea pig as a suitable model. Thirty male Dunkin-Hartley guinea pigs were divided in six groups: control, morphine, ranitidine, ranitidine+morphine, TCDD and TCDD+morphine. After previous exposure to TCDD and ranitidine, morphine effect was assessed by an increasing temperature hotplate (35-52.5°C), during 60min after morphine administration. Then, blood was collected and plasma morphine and metabolites were quantified. Animals treated with TCDD presented faster analgesic effect and 75% reached the cut-off temperature of 52.5°C, comparing with only 25% in morphine group. Animals treated with ranitidine presented a significantly lower analgesic effect, compared with morphine group (p<0.05). Moreover, significant differences between groups were found in M3G levels and M3G/morphine ratio (p<0.001 and p<0.0001), with TCDD animals presenting the highest values for M3G, M6G, M3G/morphine and M6G/morphine, and the lowest value for morphine. The opposite was observed in the animals treated with ranitidine. Our results indicate that modulation of morphine metabolism may result in variations in metabolite concentrations, leading to different analgesic responses to morphine, in an animal model that may be used to improve morphine effect in clinical practice.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Sodium phosphate monobasic, ReagentPlus®, ≥99.0%
Sigma-Aldrich
Sodium phosphate monobasic, BioReagent, for molecular biology, anhydrous, ≥98%
Sigma-Aldrich
Sodium phosphate monobasic, meets USP testing specifications, anhydrous
Sigma-Aldrich
Sodium phosphate monobasic, BioPerformance Certified, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture, ≥99.0% (titration)
Sigma-Aldrich
Morphine sulfate salt pentahydrate
Sigma-Aldrich
Phosphoric acid, BioReagent, suitable for insect cell culture, 85%
Sigma-Aldrich
Acetonitrile, anhydrous, 99.8%
Sigma-Aldrich
Phosphoric acid, ≥85 wt. % in H2O, ≥99.999% trace metals basis
Sigma-Aldrich
Phosphoric acid, 85 wt. % in H2O, 99.99% trace metals basis
Sigma-Aldrich
Phosphoric acid, crystalline, ≥99.999% trace metals basis
Sigma-Aldrich
Ranitidine hydrochloride, solid
Sigma-Aldrich
Sodium phosphate monobasic, BioXtra, ≥99.0%
Sigma-Aldrich
Sodium phosphate monobasic, 99.998% trace metals basis
Sigma-Aldrich
Sodium phosphate monobasic, purum p.a., anhydrous, ≥99.0% (T)
Supelco
Acetonitrile, analytical standard
Sigma-Aldrich
Acetonitrile, puriss. p.a., ACS reagent, ≥99.5% (GC)
Sigma-Aldrich
Sodium dodecyl sulfate solution, BioUltra, for molecular biology, 20% in H2O
Sigma-Aldrich
Phosphoric acid, BioUltra, ≥85% (T)
Sigma-Aldrich
Sodium dodecyl sulfate solution, BioUltra, for molecular biology, 10% in H2O
Sigma-Aldrich
Morphine 6-β-D-glucuronide hydrate, ≥90% (HPLC)
Supelco
Methanol solution, NMR reference standard, 4% in methanol-d4 (99.8 atom % D), NMR tube size 5 mm × 8 in.
Sigma-Aldrich
Methanol solution, NMR reference standard, 4% in methanol-d4 (99.8 atom % D), NMR tube size 3 mm × 8 in.
Supelco
Morphine-6-β-D-glucuronide solution, 100 μg/mL in methanol: water (1:1), ampule of 1 mL, certified reference material, Cerilliant®
Sigma-Aldrich
Phosphoric acid-16O4 solution, 70 wt. % in D2O, 99.9 atom % 16O
Sigma-Aldrich
Methanol-12C, 99.95 atom % 12C
Sigma-Aldrich
Sodium phosphate monobasic solution, BioUltra, 5 M in H2O
Supelco
Methanol solution, contains 0.10 % (v/v) formic acid, UHPLC, suitable for mass spectrometry (MS), ≥99.5%
Sigma-Aldrich
Acetonitrile, Preparateur, ≥99.9% (GC), One-time steel-plastic (SP) drum
Ranitidine hydrochloride, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Acetonitrile, for DNA synthesis