Cortisone and Cortisol in Maternal and Fetal Blood and in Amniotic Fluid during the Final Ten Days of Gestation in the Rabbit

Abstract

We have used instant thin-layer chromatography and radioimmunoassay to measure the concentrations of total cortisone (E) and cortisol (F) in the fetal and maternal compartments of the rabbit. The concentration of F in fetal blood increased markedly at day 25; this is just prior to the rapid increase in the surfactant phospholipids in lung tissue in this species. This increase coincided with a peak in the concentration of E and F in the maternal blood and may reflect the maternal levels. There was no ‘surge’ in the concentration of total F in fetal blood at term. The concentration of E in fetal blood varied between 5 and 15 ng/ml during this last stage of gestation, hence providing ready substrate for the 11β-reductase present in lung and other tissues. The concentration of E and F in maternal blood was significantly higher and more variable than that in blood from nonpregnant female rabbits, and there was a pronounced peak in concentration at day 30 (term: 31 days). The concentrations of both E and F in amniotic fluid were lower than those in either maternal or fetal blood until day 30 when the concentration of F increased fivefold to 19.2 ± 2.58 (mean ± SEM of 6 samples).

The relationship of body and placental weight to plasma leavels of insulin and other hormones during development in fetal rabbits

“…Mean plasma concentrations of glucagon and glucocorticoids were comparable to those observed in earlier investigations [17,28,29]. There was evidence from the 26 and 28 day age group that concentrations of glucagon were negatively correlated with fetal size, a finding consistent with observations on normal and growth-retarded guinea pigs [30].…”

Transfer of ³H-Cortisone and ³H-Cortisol between the Amniotic, Allantoic, and Fetal Blood Compartments in the Rabbit at Day 25 of Gestation

“…We have also found that whereas the fetal liver favoured reduction, the kidneys tended to oxidise E [unpublished observations]; the rabbit is sim ilar to the human fetus in this respect [12], Hence the final balance between 3H-E and 3H-F in the fetal blood would reflect the 11 (3-oxidase/reductase activities of the different tissues and their relative blood flows. In fact, we previously showed that at day 25 of gesta tion in the rabbit, the concentration of F in fetal blood greatly exceeds that of E [1], Marked species differences exist between the ability of tissues to interconvert E and F. Cer tainly in the case of the lung, the rat and rab bit readily reduce E to F [9,14,15], whereas the human fetus shows a large oxidase activ ity [12].…”

“…This involved manip ulation of both the uterus and the fetus with the possible associated risk of fetal hypother mia. Furthermore, the dose of radiolabeled steroid injected far exceeded a tracer amount, varying between 20 and 170% of the endoge nous E or F present in the amniotic compart ment at the time [1].…”

“…This represents 5 X 10"12 mol of E. We also used [l,2,6,7,n-3H]-cortisol (3H-F; 82 Ci • mmol-1) and injected either 3.92 X 10s or 6.7 X 106 dpm in 50 pi of 0.9 % NaCl, which was equiva lent to 2.2 X 10"12 or 3.7 X 10"" mol of F, respec tively. If we assume that the total volume of amniotic fluid at day 25 of gestation is 4 ml (determined by draining the amniotic sac) then the radiolabeled ste roid amounts to about 20 and 170% of the endoge nous corticoids present [1], The amniotic sacs of the different fetuses were injected with either 3H-E or 3H-F, leaving 7 min be tween each fetus. At 5, 10,20, 30,45, and 60 min after the injection, 100-pl samples of amniotic fluid were withdrawn using a 26-gauge needle and a 100 pi Hamilton syringe (Hamilton Co., Reno, Nev.).…”

“…There has been recent interest in the con centration of corticosteroids in the amniotic fluid in terms of predicting both maturity of the fetal lung [5,11,17], and function of the fetal adrenal cortex [6], In addition, a num ber of authors have suggested that injecting 1 This research was supported by a grant from the National Health and Medical Research Council of Australia.…”