OVARIAN CORTISOL METABOLISM

For the past 5 years or so, we* have been investigating the ability of human
granulosa-lutein cells (recovered from the follicular aspirates of women
hyperstimulated for IVF) to metabolize the adrenal steroid cortisol. Having
established that these cells could inactivate cortisol following enzymatic
oxidation to cortisone, (a reaction catalysed by isoforms of the enzyme
11=DF-hydroxysteroid dehydrogenase: 11=DFHSD), we were able to show that the
activity of 11=DFHSD varied dramatically between granulosa-lutein cells from
different patients and that the level of 11=DFHSD activity determined the
sensitivity of these cells to the direct actions of cortisol. Subsequently
we went on to find that high levels of cortisol oxidation in these cells
were  associated with failure to conceive by IVF-ET, whereas low ovarian
11=DFHSD activities were associated with a conception rate of around 65% per=
 ET.

In light of these findings we have been investigating the isoforms of 
11=DFH=SD active in our cell cultures and the regulation of enzyme activities. Our
kinetic studies indicate that human granulosa-lutein cell cultures express both the cloned 
type 1 11=DFHSD (acting as both an 11=DF-dehydrogenase and,= to a
lesser extent, as an 11-ketosteroid reductase) and a novel, high affinity
NADP-dependent dehydrogenase isoform (in press; Mol.Cell.Endocrinol.).
However, estimating accurate Km values for these enzymes has proven very
difficult since progesterone acts as a competitive inhibitor of 11=DFHSD
isoforms, and we have not yet taken steps to prevent our human
granulosa-lutein cell cultures from synthesizing this major steroid product.
Instead, we have systematically tested a range of steroids for their effects
on 11=DFHSD activities in intact granulosa-lutein cells and have determined
that progesterone, pregnenolone, and their 11-hydroxy-metabolites are all
potent inhibitors of 11=DFHSD whereas C19 steroids ("androgens") and
oestrogens do not appear to acutely regulate ovarian 11=DFHSD activities.
Obviously, these effects of steroids have to be characterized and taken into
account before we can investigate regulation of enzyme activities by other
endocrine factors, such as gonadotrophins. Clearly, if LH were to decrease
enzyme activities, we would need to know that this was not simply
attributable to increased progesterone synthesis, and if gonadotrophins were
to acutely increase enzyme activities, we would have to correct for the
extent to which any increase is opposed by the inevitable increased steroid
output. Our working hypothesis is that the relationship between low ovarian
11=DFHSD activities and conception in IVF-ET cycles depends upon the=
 endocrine
and paracrine regulation of 11=DFHSD prior to oocyte retrieval.

(*Tony Michael, Joe Antoniw, Becky Clarke, Tracey Collins, Marianthi
Evagelatou, Dean Norgate, Lakshmi Thaventhiran, and Brian Cooke)

Tony Michael
Biochemistry & Molecular Biology, RFHSM, London
12 / 05 / 97


Dr.Tony Michael
Lecturer in Biochemistry & Molecular Biology,
Dept.Biochemistry & Molecular Biology,                    Tel :0171-794-0500 x.4999 (Office)
Royal Free Hospital School of Medicine,                   Tel:0171-794-0500 x.4988 (Lab)
Rowland Hill Street,
Fax : 0171-794-9645
London NW3 2PF