We have recently shown that in both sheep and human pregnancies the ratio of the active glucocorticoid, cortisol (F), to its inactive 11-oxidized form, cortisone (E), in amniotic fluid increases with gestational age and is closely linked to lung maturation.
Samples (100 mg) of human amniotic membrane were obtained within 3 hours of delivery and incubated in the presence of equimolar amounts of 3H-F and 14C-E. F and E were isolated and their content of 14C and 3H allowed the calculation of %F→E and %E→F conversion. %F→E (inactivation) was arbitrarily given a negative value and the two results arithmetically summed to give the “C-11 activation index”, a measure of the net gain (or loss) of glucocorticoid activity. We found that this index increases with gestational age (n=28, slope=0.671, r=0.674, p<.001), becoming positive at 30 weeks, and reaching values of 40-50% by term.
Since glucocorticoid introduced into the amniotic fluid reaches the fetal circulation, the amniotic membrane activity is a potential source of active glucocorticoid for the fetus. Further studies will be necessary to determine if the observed activity is related to lung maturity.
(Supported by the M.R.C. of Canada)
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Tanswell, A., Worthington, D., Smith, B. et al. HUMAN AMNIOTIC MEMBRANE: A SOURCE OF ACTIVE FETAL GLUCOCORTICOIDS?. Pediatr Res 11, 412 (1977). https://doi.org/10.1203/00006450-197704000-00259