Pizzagalli F, Varga Z, Huber R D, Folkers G, Meier P J, St-Pierre M V
Division of Clinical Pharmacology and Toxicology, Department of Internal Medicine, University Hospital of Zürich, Switzerland.
J Clin Endocrinol Metab. 2003 Aug;88(8):3902-12. doi: 10.1210/jc.2003-030174.
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.
循环激素和类固醇前体的局部生物转化都是人乳腺组织中雌激素的来源。硫酸雌酮（E(1)S）是绝经前女性中一种重要的雌激素形式，硫酸脱氢表雄酮（DHEAS）是主要的肾上腺前体。研究了控制这些阴离子类固醇结合物向乳腺输送的膜转运系统。通过逆转录聚合酶链反应（RT-PCR）和Northern印迹法筛选RNA，以检测有机阴离子转运多肽（OATP）（溶质载体家族21A）和有机阴离子转运体（OAT）（溶质载体家族22A）基因家族的表达。OATP-B（SLC21A9）是主要表达的载体；OATP-D（SLC21A11）和OATP-E（SLC21A12）表达较少。在正常切片中，OATP-B免疫定位在围绕导管上皮细胞的肌上皮。在浸润性癌中，导管上皮细胞呈阳性。在稳定转染的中国仓鼠卵巢细胞中对OATP-B进行了表征。E(1)S亲和力常数（K(m)）[K(m)=5微摩尔/升，最大速度（V(max)）V(max)=777皮摩尔/毫克·分钟]和DHEAS（K(m)=9微摩尔/升，V(max)=85皮摩尔/毫克·分钟）是底物。前列腺素（PG）A(1)和PGA(2)通过使V(max)增加2倍但不改变K(m)来刺激E(1)S和DHEAS的摄取。PGA的作用被亲脂性硫醇试剂N-乙基马来酰亚胺选择性阻断，但不被亲水性乙酰氨基-4'(碘乙酰)氨基芪-2,2'-二磺酸阻断，这表明亲电子环戊烯酮环与OATP-B的特定半胱氨酸残基之间存在相互作用。
