ISOFORMS OF 11-BETA-HYDROXYSTEROID DEHYDROGENASE IN HUMAN GRANULOSA-LUTEIN CELLS

To date, two isoforms of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) have been characterized: a low affinity, NADP(+)-dependent isofo rm (11 beta HSD1) and a high affinity, NAD(+)-dependent isoform which metabolizes dexamethasone and is inhibited by cortisone (11 beta HSD2) . Having previously reported a relationship between ovarian 11 beta HS D activities and conception in women undergoing in vitro fertilization (IVF-ET), the objective of the present study was to identify which is oforms of 11 beta HSD metabolize glucocorticoids in cultures of human granulosa-lutein cells. Ln both intact cells and cell homogenates, two distinct 11 beta HSD activities were identified with differing affini ties for cortisol (K-m = 490 nM and 2.6 mu M). Even at low concentrati ons, cortisol oxidation was preferentially supported by NADP(+) and wa s independent of NAD(+). Although inhibited by the hemisuccinate ester of glycyrrhetinic acid, carbenoxolone, the predominant 11 beta HSD ac tivity in intact cells was resistant to end-product inhibition. Intact cells were also able to reduce [H-3]cortisone (K-m=190 nM) but did no t metabolize [H-3]dexamethasone. 11 beta HSD1 mRNA was expressed in 23 of 28 cell cultures whereas 11 beta HSD2 mRNA was not expressed in an y of the 22 independent cultures studied by reverse transcriptase-poly merase chain reaction (RT-PCR). We conclude that human granulosa-lutei n cells express both type 1 11 beta HSD and a novel isoform of this en zyme. While the low affinity 11 beta-dehydrogenase and Il-ketosteroid reductase activities exhibit properties consistent with 11 beta HSD1, the high affinity 11 beta-dehydrogenase differs from 11 beta HSD2 in t hat it is NADP(+)-dependent, does not metabolize dexamethasone and is resistant to end-product inhibition. (C) 1997 Elsevier Science Ireland Ltd.