Foetal-Maternal Production and Transfer of Cortisol During the Last Days of Gestation in the Guinea-Pig

Abstract

The metabolism and the rate of transfer of cortisol across the placenta in pregnant guinea-pigs and foetuses were studied by constant intravenous infusions of tritium-labelled cortisol. Estimates of endogenous and radioactive plasma cortisol levels were used to calculate the following parameters at four stages before parturition (days 62, 64, 66 and 67; parturition occurring at day 68): metabolic clearance rate; production rate; adrenal secretory rate; transfer rate from mother to foetus and from foetus to mother; irreversible removal rate; the fraction of cortisol derived from the other in the foetal and maternal vascular compartments; the fraction of secreted and recycled cortisol involved in the transfer. The metabolic clearance rate and the rates of production and secretion of cortisol were higher in the mother than in the foetus between days 62 and 67 of gestation. About 90% of the foetal cortisol was of maternal origin. The fraction of maternal cortisol of foetal origin increased in the last days of gestation.

Maturation of glucocorticosteroid activity in the foetal guinea-pig during the end of gestation

“…High plasma PBG levels were associated with very low progesterone TCM during gestation (Illingworth et at., 1970). Similarly, high transcortin plasma levels paralleled a low cortisol TCM (3 times lower than in non-pregnant females) (Dalle and Delost, 1979).…”

“…These high levels result from a regular rise in foetal plasma cortisol levels during the last days of gestation, which parallels the increase in maternal plasma and adrenal cortisol concentrations, foetal adrenal cortisol content increasing only during the last 24 hrs of gestation (Dalle and Delost, 1976). Recent studies (Dalle and Delost, 1979) Murphy (1967), modified as described previously (Dalle and Delost, 1976). Cortisol binding parameters were determined using the method of Pearlman and Crepy (1967), adapted for corticosteroids (Pradier, 1979 Free and bound cortisol levels in the foetus ( fig.…”

“…This increased rate might result from a response of the adrenals to the stress associated with the onset of labor. At that time, the transfer of cortisol across the placenta from the foetus to the mother equals that from the mother to the foetus (Dalle and Delost, 1979).…”

Plasma Calcium Homeostasis in the Guinea Pig during the Perinatal Period

“…After palpation, laparotomy was performed just above the neck of 1 fetus to insert a polyethylene catheter (Bio trol No. 1) in one carotid artery [5,16].…”

The effects of psychosomatic stress at the end of pregnancy on maternal and fetal plasma cortisol levels and liver glycogen in guinea-pigs

“…Measurements of adrenal secretion rates in acute experiments (Dalle and Delost, 1979) have shown that the maternal adrenals are the principal source of the cortisol found in both the maternal and the fetal pools.…”