title: CYP3A in horse intestines.
abstract: The intestinal enterocytes provide the initial site for cytochrome P450 (CYP)-mediated metabolism of orally absorbed xenobiotics. In man and some animal species, the CYP3A subfamily is highly expressed in the intestines and considered to be important in the first-pass metabolism of drugs and other xenobiotics. The aim of the present study was to investigate the mRNA expression, immunohistochemical localization and catalytic activity of CYP3A in the intestines of horse. Real-time RT-PCR analyses showed that the highest CYP3A mRNA expression was present in the duodenum with a decreasing level towards jejunum, ileum, cecum, and colon. The CYP3A mRNA expression in the liver was similar as in the anterior part of the jejunum, but about 4.5 times lower than in the anterior part of the duodenum. Immunohistochemistry showed CYP3A immunoreactivity in the cytoplasm of the enterocytes, which decreased distally along the intestinal tract. CYP3A-dependent metabolic activity rose slightly from the anterior to the distal part of the duodenum and the anterior part of the jejunum and then declined to the middle and distal parts of the jejunum and the ileum, cecum, and colon. Our results suggest that CYP3A in the small intestine plays a major role in first-pass metabolism and may affect bioavailability and therapeutic efficiency of some orally administrated drugs in horse.
authors.affiliation: Department of Biomedical Sciences and Veterinary Public Health, Division of Pathology, Pharmacology and Toxicology, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Tydén
authors.forename: Lena
authors.initials: L
authors.lastname: Olsén
authors.forename: Jonas
authors.initials: J
authors.lastname: Tallkvist
authors.forename: Pia
authors.initials: P
authors.lastname: Larsson
authors.forename: Hans
authors.initials: H
authors.lastname: Tjälve
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics* / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D006736:Horses / Q000378:metabolism*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007422:Intestines / Q000201:enzymology*; D008861:Microsomes / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics* / Q000378:metabolism*; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D012313:RNA; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; D010089:Oxidoreductases, N-Demethylating