Steroid
hydroxylase gene expression in the ovine fetal adrenal gland following ACTH infusion
Kathy Tangalakis, John P. Coghlan, Robert Crawford, Vicki E. Howard Florey Institute
Marelyn Wintour
of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, Australia
Abstract. Between 90 and 120
days of gestation (term cortisol concentrations in the fetus are at a minimum, levels of mRNA encoding the steroidogenic enzymes 17\g=a\-hydroxylase (P-45017\g=a\) and cholesterol side-chain cleavage (P-450scc) are also very low. Over the following 30 days, P-45017\g=a\and P-450scc gene expression increases concurrent with increasing fetal cortisol concentration. The hypothesis tested in this study was that cortisol biosynthesis is minimal in the period 90-120 days because of insufficient ACTH. Fetuses were cannulated between 98-102 days of gestation. Following recovery, 7 fetuses received 24-h ACTH infusions (12 \g=m\g/24h) and 5 fetuses received 24-h vehicle infusions; 4 ACTH-infused and 4 vehicle-infused fetuses were then sacrificed immediately after cessation of the infusion. The other fetuses were left in utero for 3 days prior to sacrifice. Fetal blood samples were analysed for ACTH and cortisol and the adrenals processed for hybridization histochemistry and Northern blot analysis. ACTH, but not vehicle, induced significant increases in the width of the adrenal cortex and in the levels of P-45017\g=a\and P\x=req-\ 450scc mRNA. Concurrently, fetal plasma ACTH and cortisol concentrations also increased significantly. In adrenals from fetuses left in utero for 3 days after cessation of the ACTH infusion, P-45017\g=a\and P-450scc mRNA levels returned to control levels. Plasma ACTH and cortisol levels also approximated basal values. P-450c21 mRNA levels did not vary significantly at any time with the treatments. It can be concluded that the major regulatory influence on ACTH in the 90-120 day fetus is via increased gene expression of P-45017\g=a\and P-450scc but not P-450c21. =
Hammond and E.
147\m=+-\5),when plasma
In the
sheep, the duration of pregnancy is approx¬ imately 150 days and parturition is preceded by intense activation of the fetal adrenal cortex (1-3). The adrenal gland is visible grossly by 28 days of
gestation, attached by a stalk to the fetal kidney (4). Two morphologically distinct zones are present in the cortex by day 60, and the outer zone has all the characteristics of the adult zona glomerulosa by day 80 (5). The inner zone cells do not begin to take on the morphological characteristics of adult zona fasciculata cells until after 120-125 days of gestation (5). However, the steroid producing capacity of the
ovine fetal adrenal follows a different pattern. When incubated in vitro with adrenocorticotropin (ACTH), fetal adrenal cells can produce relatively large quantities of cortisol both early (40-90 days) and late (125-150 days) in gestation, but not in the middle period (90-120 days) (6-8). The small amount of cortisol in fetal blood in this middle period (
hydroxylase gene expression in the ovine fetal adrenal gland following ACTH infusion
Kathy Tangalakis, John P. Coghlan, Robert Crawford, Vicki E. Howard Florey Institute
Marelyn Wintour
of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, Australia
Abstract. Between 90 and 120
days of gestation (term cortisol concentrations in the fetus are at a minimum, levels of mRNA encoding the steroidogenic enzymes 17\g=a\-hydroxylase (P-45017\g=a\) and cholesterol side-chain cleavage (P-450scc) are also very low. Over the following 30 days, P-45017\g=a\and P-450scc gene expression increases concurrent with increasing fetal cortisol concentration. The hypothesis tested in this study was that cortisol biosynthesis is minimal in the period 90-120 days because of insufficient ACTH. Fetuses were cannulated between 98-102 days of gestation. Following recovery, 7 fetuses received 24-h ACTH infusions (12 \g=m\g/24h) and 5 fetuses received 24-h vehicle infusions; 4 ACTH-infused and 4 vehicle-infused fetuses were then sacrificed immediately after cessation of the infusion. The other fetuses were left in utero for 3 days prior to sacrifice. Fetal blood samples were analysed for ACTH and cortisol and the adrenals processed for hybridization histochemistry and Northern blot analysis. ACTH, but not vehicle, induced significant increases in the width of the adrenal cortex and in the levels of P-45017\g=a\and P\x=req-\ 450scc mRNA. Concurrently, fetal plasma ACTH and cortisol concentrations also increased significantly. In adrenals from fetuses left in utero for 3 days after cessation of the ACTH infusion, P-45017\g=a\and P-450scc mRNA levels returned to control levels. Plasma ACTH and cortisol levels also approximated basal values. P-450c21 mRNA levels did not vary significantly at any time with the treatments. It can be concluded that the major regulatory influence on ACTH in the 90-120 day fetus is via increased gene expression of P-45017\g=a\and P-450scc but not P-450c21. =
Hammond and E.
147\m=+-\5),when plasma
In the
sheep, the duration of pregnancy is approx¬ imately 150 days and parturition is preceded by intense activation of the fetal adrenal cortex (1-3). The adrenal gland is visible grossly by 28 days of
gestation, attached by a stalk to the fetal kidney (4). Two morphologically distinct zones are present in the cortex by day 60, and the outer zone has all the characteristics of the adult zona glomerulosa by day 80 (5). The inner zone cells do not begin to take on the morphological characteristics of adult zona fasciculata cells until after 120-125 days of gestation (5). However, the steroid producing capacity of the
ovine fetal adrenal follows a different pattern. When incubated in vitro with adrenocorticotropin (ACTH), fetal adrenal cells can produce relatively large quantities of cortisol both early (40-90 days) and late (125-150 days) in gestation, but not in the middle period (90-120 days) (6-8). The small amount of cortisol in fetal blood in this middle period (
