title: Age-related Differences in CYP3A Abundance and Activity in the Liver of the Göttingen Minipig.
abstract: In view of paediatric drug development, regulatory authorities often request safety studies in juvenile animals, including minipigs. Unfortunately, knowledge on the ontogeny of the biotransformation processes in animal models remains scarce and impedes a correct interpretation of the toxicity findings. CYP3A4 is one of the most important drug-metabolizing enzymes in human beings and shows important similarities with CYP3A in the minipig. Therefore, the aim of this study was to assess the abundance and activity of CYP3A in liver microsomes from foetal, juvenile (days 1, 3, 7 and 28) and adult male and female Göttingen minipigs. CYP3A abundance was studied by an indirect enzyme-linked immunosorbent assay (ELISA), whereas CYP3A activity was assessed by a biotransformation assay with Luciferin-IPA. CYP3A abundance could not be detected until day 3. From day 7 onwards, a gradual increase in expression was noted, leading to the highest abundance in adult animals. CYP3A activity was not detectable in foetuses and 1-day-old animals. The CYP3A activity was detectable, but below the LLOQ in day 3 animals and increased gradually with age to reach the highest level in adults. The CYP3cide and ketoconazole inhibition, and testosterone and midazolam reduction of Luciferin-IPA metabolism in minipig liver microsomes substantiate that Luciferin-IPA is metabolized by CYP3A in minipigs. A positive correlation was found between CYP3A abundance and biotransformation of Luciferin-IPA (Pearson r = 0.863; p < 0.0001). In conclusion, both abundance and activity of CYP3A increased gradually in juvenile minipigs, but remained below the levels observed in adult animals.
authors.affiliation: Applied Veterinary Morphology, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium.
authors.forename: Els
authors.initials: E
authors.lastname: Van Peer
authors.affiliation: Laboratory of Medical Biochemistry and Clinical Analysis, Department of Bioanalysis, Ghent University, Ghent, Belgium.
authors.forename: Lies
authors.initials: L
authors.lastname: De Bock
authors.affiliation: Laboratory of Medical Biochemistry and Clinical Analysis, Department of Bioanalysis, Ghent University, Ghent, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Boussery
authors.affiliation: Laboratory of Medical Biochemistry and Clinical Analysis, Department of Bioanalysis, Ghent University, Ghent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Van Bocxlaer
authors.affiliation: Applied Veterinary Morphology, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium.
authors.forename: Christophe
authors.initials: C
authors.lastname: Casteleyn
authors.affiliation: Applied Veterinary Morphology, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium.
authors.forename: Chris
authors.initials: C
authors.lastname: Van Ginneken
authors.affiliation: Applied Veterinary Morphology, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Van Cruchten
mesh_terms: D000367:Age Factors; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001711:Biotransformation; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D049454:Firefly Luciferin / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D013379:Substrate Specificity; D013552:Swine / Q000378:metabolism*; D013556:Swine, Miniature / Q000378:metabolism*
chemical_list: D049454:Firefly Luciferin; D051544:Cytochrome P-450 CYP3A