Cortisol concentrations in fetal fluids of the tammar wallaby increased dramatically over the last 7-8% of pregnancy. This pattern is found in all eutherian species that have been studied and is reported here for the first time in a marsupial. The source of rising cortisol is likely to be the fetal adrenal, because its cortisol content parallels the increases in fetal fluids during this period. Production of cortisol by fetal adrenals in vitro is stimulated by ACTH and PGE2, suggesting that the fetal pituitary and placenta may provide the stimulus for increased cortisol in vivo. Within 24 h postpartum, cortisol in neonatal plasma and adrenals decreases to low levels. These results clearly indicate that fetal adrenal cortisol synthesis increases at the end of pregnancy and that it is responsive to trophic stimulation from ACTH and PGE2 during this period. Thus, despite the dramatic differences in the developmental profiles of marsupial and eutherian mammals, maturation of the fetal adrenal and increasing levels of fetal cortisol may be a common event at parturition. ventolin 100 mcg
The profiles for increasing cortisol concentration were similar in all fetal fluids and adrenal tissue over the period examined, and levels were comparable in YSF, allantoic fluid, and fetal plasma. On each day of pregnancy, variability in measured cortisol concentrations was high. Some of this variation may be explained by the methodological difficulties of collecting samples from the different fetal compartments of the tiny marsupial fetus, which weighs only 400 mg at birth. However, much of the variability appears to be due to small differences in the timing of fetal maturation and the rapidity of the change occurring in the last 2 days of gestation: in this species, the entire period of organogensis takes only 7 days.