Developmental expression of bovine adrenocortical steroid hydroxylases. Regulation of P-450(17 alpha) expression leads to episodic fetal cortisol production.
The developmental expression of adrenocortical steroid hydroxylases was studied in bovine fetuses from 40 to 280 days gestational age. The expression of P-450(17 alpha) is first detected at a gestational age of 50 days and reaches a maximum at 60-70 days. The expression of P-450(17 alpha) then declines and is nondetectable at a gestational age of 100 days. P-450(17 alpha) is not expressed again until about 240 days, i.e. shortly before birth (approximately 280 days). P-450scc, P-450c21, P-450(11 beta) and adrenodoxin were present in fetal adrenals throughout gestation. This "on-off-on" pattern of P-450(17 alpha) expression during fetal development was associated with a corresponding episodic production of cortisol. Immunoreactive corticotropin (ACTH) levels in fetal plasma were elevated in small fetuses (corresponding to less than or equal to 100 days) and in near-term fetuses (corresponding to greater than 250 days) compared with those in mid-gestation fetuses. In primary culture, adrenal cells from mid-gestation fetuses contained no detectable P-450(17 alpha) but rapidly responded to ACTH with an increase in P-450(17 alpha) protein and mRNA. The tissue specificity of the developmental patterns is emphasized by the fact that both P-450(17 alpha) and P-450scc were detectable throughout the development of the fetal testes, whereas only P-450scc was detectable in fetal bovine ovary prior to 200 days. Thus, in fetal bovine adrenal it appears that ACTH is the major regulatory factor effecting the intermittent presence of P-450(17 alpha), whereas the presence of the other steroid hydroxylases is either regulated by additional factors or shows a much different sensitivity to ACTH.
Lund
J
J
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas 75235.
Faucher
D J
DJ
Ford
S P
SP
Porter
J C
JC
Waterman
M R
MR
Mason
J I
JI
D000302:Adrenal Cortex / Q000196:embryology / Q000201:enzymology*; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002417:Cattle; D002478:Cells, Cultured; D003345:Corticosterone / Q000096:biosynthesis; D004591:Electrophoresis, Polyacrylamide Gel; D005333:Fetus / Q000378:metabolism / Q000502:physiology; D005865:Gestational Age; D006854:Hydrocortisone / Q000096:biosynthesis*; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*
D013250:Steroid Hydroxylases; D013254:Steroid 17-alpha-Hydroxylase; D003345:Corticosterone; D006854:Hydrocortisone