Identification of steroid sulfate transport processes in the human mammary gland.
Circulating hormones and local biotransformation of steroid precursors are both sources of estrogen in human mammary tissue. Estrone-3-sulfate (E(1)S) is an important estrogenic form in premenopausal women, and dehydroepiandrosterone sulfate (DHEAS) constitutes a major adrenal precursor. Membrane transport systems that govern delivery of these anionic steroid conjugates to the mammary gland were investigated. RNA was screened by RT-PCR and Northern blotting for expression of organic anion transporting polypeptide (OATP) (solute carrier family 21A) and organic anion transporter (OAT) (solute carrier family 22A) gene families. OATP-B (SLC21A9) was the major carrier expressed; OATP-D (SLC21A11) and OATP-E (SLC21A12) were less abundant. In normal sections, OATP-B immunolocalized to the myoepithelium that surrounds the ductal epithelial cells. In invasive carcinoma, ductal epithelial cells were positive. OATP-B was characterized in stable transfected Chinese hamster ovary cells. E(1)S affinity constant (K(m)) [K(m) = 5 micro mol/liter, maximum velocity (V(max)) V(max) = 777 pmol/mg.min] and DHEAS (K(m) = 9 micro mol/liter, V(max) = 85 pmol/mg.min) were substrates. The prostaglandins (PG) A(1) and PGA(2) stimulated uptake of E(1)S and DHEAS by increasing V(max) 2-fold but not changing K(m). The effect of PGA was selectively blocked by the lipophilic thiol reagent N-ethylmaleimide but not by the hydrophilic acetamido-4'(iodoacetyl)aminostilbene-2,2'-disulfonic acid, suggesting an interaction between the electrophilic cyclopentenone ring and specific cysteine residues of OATP-B.
Pizzagalli
F
F
Division of Clinical Pharmacology and Toxicology, Department of Internal Medicine, University Hospital of Zürich, Switzerland.
Varga
Z
Z
Huber
R D
RD
Folkers
G
G
Meier
P J
PJ
St-Pierre
M V
MV
D000465:Algorithms; D000818:Animals; D001693:Biological Transport, Active; D015152:Blotting, Northern; D001940:Breast / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D019314:Dehydroepiandrosterone Sulfate / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D004970:Estrone / Q000031:analogs & derivatives* / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D027361:Organic Anion Transporters / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013256:Steroids / Q000378:metabolism*; D013431:Sulfates / Q000378:metabolism; D014162:Transfection
D027361:Organic Anion Transporters; D013256:Steroids; D013431:Sulfates; D004970:Estrone; D019314:Dehydroepiandrosterone Sulfate; C017296:estrone sulfate