Regulation by Adrenocorticotropin (ACTH), Angiotensin II, Transforming Growth Factor-β, and Insulin-Like Growth Factor I of Bovine Adrenal Cell Steroidogenic Capacity and Expression of ACTH Receptor, Steroidogenic Acute Regulatory Protein, Cytochrome P450c17, and 3β-Hydroxysteroid Dehydrogenase1

• Published in: Endocrinology (Philadelphia) Vol. 141; no. 5; pp. 1599 - 1607
• Main Authors: Le Roy, Christine, Li, J. Yuan, Stocco, Douglas M, Langlois, Dominique, Saez, José M
• Format: Journal Article
• Language: English
• Published: Endocrine Society 01-05-2000
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/endo.141.5.7457

The purpose of this study was to evaluate the time-course effect of a
36-h treatment with ACTH (10−8 m),
transforming growth factor-β1 (TGFβ1; 10−10
m), angiotensin II (AngII; 10−7
m), and insulin-like growth factor I (IGF-I;
10−8 m) on the steroidogenic capacity of
bovine adrenocortical cells (BAC) and on messenger RNA (mRNA) levels of
ACTH receptor, cytochrome P450c17, 3β-hydroxysteroid dehydrogenase
(3βHSD), steroidogenic acute regulatory protein (StAR), and StAR
protein. ACTH and IGF-I enhanced, in a time-dependent manner, the acute
2-h ACTH-induced cortisol production, whereas TGFβ1 and AngII
markedly reduced it. ACTH, IGF-I, and AngII increased ACTH receptor
mRNA, but the opposite was observed after TGFβ1 treatment. ACTH and
IGF-I increased P450c17 and 3βHSD mRNAs, whereas AngII and TGFβ1
had the opposite effects. However, the effects of the four peptides on
ACTH-induced cortisol production appeared before any significant
alterations of the mRNA levels occurred. The most marked and rapid
effect of the four peptides was on StAR mRNA. The stimulatory effect of
ACTH was seen within 1.5 h, peaked at 4–6 h, and declined
thereafter, but at the end of the 36-h pretreatment, the levels of StAR
mRNA and protein were higher than those in control cells. IGF-I also
enhanced StAR mRNA levels within 1.5 h, and these levels remained
fairly constant. The effects of AngII on StAR mRNA expression were
biphasic, with a peak within 1.5–3 h, followed by a rapid decline to
almost undetectable levels of both mRNA and protein. TGFβ1 had no
significant effect during the first 3 h, but thereafter StAR mRNA
declined, and at the end of the experiment the StAR mRNA and protein
were almost undetectable. Similar results were observed when cells were
treated with ACTH plus TGFβ1. A 2-h acute ACTH stimulation at the end
of the 36-h pretreatment caused a higher increase in StAR mRNA and
protein in ACTH- or IGF-I-pretreated cells than in control cells,
which, in turn, had higher levels than cells pretreated with TGFβ1,
ACTH plus TGFβ1, or AngII.
These results and the fact that the stimulatory (IGF-I) or inhibitory
(AngII and TGFβ1) effects on ACTH-induced cortisol production were
more pronounced than those on the ability of cells to transform
pregnenolone into cortisol strongly suggest that regulation of StAR
expression is one of the main factors, but not the only one, involved
in the positive (IGF-I) or negative (TGFβ1 and AngII) regulation of
BAC for ACTH steroidogenic responsiveness. A high correlation between
steady state mRNA level and acute ACTH-induced cortisol production
favors this conclusion.