title: Metabolism of testosterone during in vitro transport across CACO-2 cell monolayers: evidence for beta-hydroxysteroid dehydrogenase activity in differentiated CACO-2 cells.
abstract: Testosterone has previously been used as a model compound for the determination of unstirred water layer thickness in the CACO-2 transport model. We have found, however, that testosterone is metabolized during in vitro transport across the CACO-2 cell monolayers. This suggests that testosterone is not an ideal model substance. Testosterone is metabolized to androstenedione, indicating the formation of 17-beta-hydroxysteroid dehydrogenase by differentiated CACO-2 cells. No reverse metabolism is observed, thus androstenedione is considered superior to testosterone for determination of unstirred water layer thickness in the CACO-2 system. Permeability coefficients for testosterone and androstenedione obtained under identical transport conditions were 66 (+/- 7) * 10(-6) (n = 26) and 84 (+/- 7) * 10(-6) (n = 9) cm/sec, respectively. The unstirred water layer thicknesses at different agitation rates are determined for the CACO-2 transport model used in our laboratory utilizing androstenedione as a model compound. The system is capable of controlling the water layer thickness from about 200 to 1000 microns.
authors.affiliation: Royal Danish School of Pharmacy, Department of Pharmaceutical Chemistry, Copenhagen.
authors.forename: A
authors.initials: A
authors.lastname: Buur
authors.forename: N
authors.initials: N
authors.lastname: Mørk
mesh_terms: D000735:Androstenedione / Q000378:metabolism; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases / Q000378:metabolism*; D013058:Mass Spectrometry; D010539:Permeability; D013056:Spectrophotometry, Ultraviolet; D013739:Testosterone / Q000378:metabolism*
chemical_list: D013739:Testosterone; D000735:Androstenedione; D006913:Hydroxysteroid Dehydrogenases