The role of fetal adrenal hormones in the switch from fetal to adult globin synthesis in the sheep.
The switch from gamma (fetal) to beta (adult) globin production was studied by the analysis of globin synthesis in chronically cannulated ovine fetuses and newborn lambs. The gamma/alpha globin synthesis ratio decreased from 0.98 +/- 0.11 (S.D.) (n = 4 samples) at 100-120 days of gestation to 0.15 +/- 0.07 (n = 4) in lambs of 150-156 days post-conception, and the beta/alpha synthesis ratio increased from 0.04 +/- 0.06 (n = 4) to 1.13 +/- 0.21 (n = 4) over the same period. In bilaterally adrenalectomized fetuses, which survived in utero until 151-156 days, the gamma/alpha and beta/alpha synthesis ratios were 0.64 +/- 0.14 (n = 3) and 0.25 +/- 0.07 (n = 3) respectively in the 150- to 156-day period. Bilateral adrenalectomy did not affect the time of onset of beta globin synthesis, but significantly decreased the rate. In one bilaterally adrenalectomized fetus the infusion of increasing concentrations of cortisol restored the rate of beta globin synthesis to normal. Treatment of three intact fetuses with 100 micrograms cortisol/h for 3 weeks, from 100 to 121 days, did not affect the timing or rate of switch from gamma to beta globin synthesis. Thus fetal adrenal secretions, probably cortisol, affected the rate of change of gamma to beta globin synthesis but other factors must have been involved in the initiation of the switch.
D000305:Adrenal Cortex Hormones / Q000502:physiology*; D000311:Adrenal Glands / Q000196:embryology* / Q000378:metabolism; D000315:Adrenalectomy; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D005312:Fetal Blood / Q000378:metabolism; D005333:Fetus / Q000378:metabolism*; D005865:Gestational Age; D005914:Globins / Q000096:biosynthesis*; D006854:Hydrocortisone / Q000097:blood / Q000494:pharmacology / Q000502:physiology; D012756:Sheep
D000305:Adrenal Cortex Hormones; D005914:Globins; D006854:Hydrocortisone