Formation of 6 beta-hydroxydexamethasone from dexamethasone by A6 cells

A6 cells, a continuous cell line derived from kidney of Xenopus laevis, were incubated with [3H]-dexamethasone for 24 h. When radioactive compounds in media were separated by reversed phase high pressure liquid chromatography, two radioactive fractions were found. The less polar fraction which contained 91-93% of total radioactivity cochromatographed with dexamethasone, whereas the polar fraction contained 5% of total radioactivity in media. In order to rigorously identify the polar metabolite, large scale cultures were carried out and the polar compound was separated and purified by reversed phase high pressure liquid chromatography. The purified material was analyzed by secondary ion mass spectrometry and nuclear magnetic resonance spectroscopy. By these procedures, this material was identified as 6 beta-hydroxydexamethasone. To our knowledge these are the first data indicating that dexamethasone can be metabolized by transporting epithelia such as A6 cells.