Hormonal regulation of adrenal microvillar channel formation.
This study examined the in vivo relationship between expression of the HDL receptor scavenger receptor class B (SR-BI) and corresponding structural changes in the rat adrenocortical cell microvillar compartment. Using hormonal stimulation and withdrawal protocols, we were able to manipulate adrenal SR-BI levels and carry out qualitative and quantitative measurements correlating SR-BI expression with microvillar mass and microvillar channel formation. Young male rats were used as controls or treated with adrenocorticotropin hormone (ACTH) (24 h), 17alpha-ethinyl estradiol (17alpha-E2) (5 days), or dexamethasone (DEX) (24 h). Quantitative Western blot analysis and immunocytochemistry indicated that ACTH and 17alpha-E2 treatment greatly increased SR-BI expression in the adrenal (especially in the microvillar compartment of adrenocortical cells), whereas DEX treatment led to a decrease of SR-BI by all measurements. At the same time, striking ultrastructural changes occurred in the adrenocortical cell microvillar compartment: e.g., microvillar area and microvillar channel formation and complexity dramatically increased (compared with control values) after ACTH or 17alpha-E2 treatment, whereas the same values declined after DEX treatment. These measurements illustrate the exceptional flexibility and responsiveness of the microvillar compartment to hormonal stimuli, and suggest that regulation of SR-BI expression and structural configuration of the surface of steroidogenic cells goes hand in hand.
Azhar
Salman
S
Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304, USA.
Nomoto
Ann
A
Reaven
Eve
E
D000311:Adrenal Glands / Q000502:physiology* / Q000648:ultrastructure; D000324:Adrenocorticotropic Hormone / Q000502:physiology*; D000818:Animals; D018955:CD36 Antigens / Q000096:biosynthesis* / Q000235:genetics; D002784:Cholesterol / Q000097:blood / Q000378:metabolism; D003345:Corticosterone / Q000378:metabolism; D004958:Estradiol / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins; D008871:Microvilli / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B
D018955:CD36 Antigens; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; C495125:Scarb1 protein, rat; D051122:Scavenger Receptors, Class B; D004958:Estradiol; D000324:Adrenocorticotropic Hormone; D002784:Cholesterol; D003345:Corticosterone