Steroidogenic adrenocortical cells synthesize alpha 2-macroglobulin in vitro, not in vivo.
We previously identified alpha 2-macroglobulin as the major protein secreted by primary cultures of adrenocortical cells. We report here that in the adrenal gland, the distribution of alpha 2-macroglobulin in the adrenocortical tissue is restricted to the endothelium of blood vessels and that no immunoreactivity is found in steroidogenic cells. A time course study revealed that freshly dissociated bovine adrenocortical cells were void of alpha 2-macroglobulin immunoreactivity whereas the proportion of alpha 2-macroglobulin-positive cells reached more than two-thirds of the population between day 4 and day 7 of culture. Double immunoenzymatic labeling of 6-day-old cultures revealed a co-localization of alpha 2-macroglobulin and the steroidogenic enzyme P-450SCC. Treatment of 5-day-old cultures (expressing alpha 2-macroglobulin) for 24 h by either ACTH (10(-9)-10(-6) M) or alpha 2-macroglobulin (2.5 mg/ml) resulted in a marked decrease of the expression of alpha 2-macroglobulin. These data indicate that ACTH and plasmatic alpha 2-macroglobulin could physiologically repress alpha 2-macroglobulin expression in the adrenal cortex in vivo.
Negoescu
A
A
INSERM Unité 244, CEA, Département de Biologie Moléculaire et Structurale, CEN-G, Grenoble, France.
Labat-Moleur
F
F
Brambilla
E
E
Chambaz
E M
EM
Feige
J J
JJ
D000302:Adrenal Cortex / Q000098:blood supply / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000032:analysis / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D013997:Time Factors; D000511:alpha-Macroglobulins / Q000032:analysis / Q000096:biosynthesis* / Q000494:pharmacology
D000511:alpha-Macroglobulins; D000324:Adrenocorticotropic Hormone; D002786:Cholesterol Side-Chain Cleavage Enzyme