No abstract

Concentrations of both cortisol and cortisone were significantly lower in FF samples obtained from patients that conceived by IVF-ET than in those obtained from nonconception cycles. Conception by gonadotrophin-stimulated IVF-ET was associated with an elevated intrafollicular ratio of cortisol:cortisone, consistent with a low level of intraovarian cortisol oxidation by 11betaHSD.

In the ovary, cortisol-cortisone interconversion is catalysed by isoforms of 11beta-hydroxysteroid dehydrogenase (11betaHSD). The objective of this study was to establish whether human follicular fluid (hFF), obtained after controlled ovarian hyperstimulation, contains paracrine modulators of 11betaHSD activity. Of 274 hFF samples tested for effects in rat kidney homogenates, 206 hFF samples significantly inhibited NADP(+)-dependent oxidation of cortisol within 1 h (by 11-67% of control 11betaHSD activity), whereas 42 hFF samples significantly stimulated 11betaHSD activity (16-210% increase relative to control). Although charcoal-stripping of hFF prevented the inhibition and potentiated the stimulation of NADP(+)-dependent cortisol oxidation in a renal homogenate, effects of individual hFF samples on NADP(+)-dependent cortisol oxidation were independent of intrafollicular progesterone concentrations. Hydrophilic fractions of hFF samples, isolated by C18 column chromatography, stimulated both the NADP(+)-dependent oxidation of cortisol (by 55+/-5%, n=98) and the NADPH-dependent reduction of cortisone (by 86+/-22%, n= 5). In contrast, the hydrophobic fractions of hFF (eluted at 65-85% methanol) inhibited both NADP(+)-dependent 11beta-dehydrogenase and NADPH-dependent 11-ketosteroid reductase activities (by 63+/-2% and 74+/-4%, respectively). None of the C18 column fractions of 50 hFF samples had any significant effect on NAD(+)-dependent 11beta-dehydrogenase activities. The hydrophobic inhibitors of NADP(H)-dependent cortisol-cortisone metabolism did not co-elute with several candidate compounds (prostaglandins E(2) and F(2alpha), cortisol, cortisone, oestradiol, testosterone, progesterone, pregnenolone or cholesterol). Hence, hFF aspirated from women undergoing controlled ovarian hyperstimulation for assisted conception contains both hydrophilic stimuli and hydrophobic inhibitors of glucocorticoid metabolism which appear to be selective for the NADP(H)-dependent, type 1 isoform of 11betaHSD.

1. The type 2 isoform of 11beta-hydroxysteroid dehydrogenase, an enzyme which converts cortisol or corticosterone to inactive 11-ketosteroid metabolites, is thought to be responsible for preventing access of endogenous glucocorticoids to mineralocorticoid receptors in the distal nephron; although direct in vivo evidence for this is still lacking. We have examined whether graded inhibition of renal 11beta-hydroxysteroid dehydrogenase activities in vivo results in corresponding changes in urinary electrolyte excretion due to exposure of mineralocorticoid receptors to circulating endogenous glucocorticoids.2. Anaesthetized rats were infused intravenously with vehicle alone or with one of three doses of carbenoxolone: 0.06, 0.6 or 6 mg/h. After measurement of renal electrolyte excretion, the kidneys were snap-frozen in liquid nitrogen and 11beta-hydroxysteroid dehydrogenase activities were measured directly by enzyme assay in the presence of NAD+ or NADP+.3. A dose-dependent inhibition of renal 11beta-hydroxysteroid dehydrogenase activities was observed: the low, intermediate and high doses of carbenoxolone causing approximately 50%, 80% and >90% inhibition respectively. Only with the high dose was an effect on renal function observed (decreased fractional Na+ excretion and urinary Na+/K+ ratio).4. The poor correlation between the extent of inhibition of renal 11beta-hydroxysteroid dehydrogenase and altered urinary Na+ excretion, apparent at the lower doses of carbenoxolone, suggests either that 11beta-hydroxysteroid dehydrogenase has considerable functional reserve, or that it may not be the only mechanism determining mineralocorticoid receptor specificity in the distal nephron.