ABCMdb

PMID: 16895976

Sun H, Liu L, Pang KS
Increased estrogen sulfation of estradiol 17beta-D-glucuronide in metastatic tumor rat livers.
J Pharmacol Exp Ther. 2006 Nov;319(2):818-31. Epub 2006 Aug 8., [PubMed]

Sentences

No. Mutations Sentence Comment

38 ABCC3 p.Ser17Gly E2335 S17G was biosynthesized by recirculation of 0.5 ␮M E217G in oxygenated Krebs-Henseleit bicarbonate (KHB) at 40 ml/min through the liver, with Na2 35 SO4 (18 ␮Ci/min for 30 min) that was infused directly into the portal vein cannula. Login to comment 39 ABCC3 p.Ser17Gly The pooled bile was lyophilized, reconstituted, and injected into HPLC running gradient program I for isolation (see HPLC Methods); the eluant corresponding to E2335 S17G was desalted by a reverse phase Sep-Pak cartridge (Waters, MA), and the purified content was stored at -20°C. Login to comment 40 ABCC3 p.Ser17Gly The radiochemical purities of [3 H]E217G, [3 H]E1S, and E2335 S17G were 98, 99, and 95%, respectively, as evaluated by HPLC. Login to comment 128 ABCC3 p.Ser17Gly Sulfatase Activity in Subcellular Fractions An aliquot (75 ␮l) of microsomal (0.3 mg) or cytosolic (0.7 mg) fraction was mixed with 75 ␮l of E2335 S17G (ϳ50,000 dpm) in Tris-HCl (25 mM, pH 7.4). Login to comment 132 ABCC3 p.Ser17Gly The reconstituted solution was injected into HPLC running program III (see under HPLC Methods) for desulfation of E2335 S17G. Login to comment 135 ABCC3 p.Ser17Gly Hence, parallel studies were conducted to estimate sulfatase activity by formation of 35 SO4 2- from E2335 S17G and [3 H]E1 from [3 H]E1S. Login to comment 136 ABCC3 p.Ser17Gly The desulfation intrinsic clearances were estimated as the ratio of desulfation rate to E2335 S17G or [3 H]E1S concentration at time 0. Login to comment 153 ABCC3 p.Ser17Gly Program III was capable of separating 35 SO4 2- (RT ϳ3 min) and E2335 S17G (RT ϳ18 min) well. Login to comment 225 ABCC3 p.Ser17Gly ABCC3 p.Ser17Gly Futile Cycling: Sulfatase Activity in Subcellular Fractions The retention time of the E2335 S17G deviated slightly from that of the E2335 S17G standard in buffer because of the presence of different matrices during workup from the microsomal and cytosolic incubation samples (Fig. 4). Login to comment 226 ABCC3 p.Ser17Gly Only the microsomal but not the cytosolic fraction demonstrated desulfation activities toward E2335 S17G to form the product, 35 SO4 2- , as shown in the HPLC tracings. Login to comment 227 ABCC3 p.Ser17Gly However, the desulfation activities toward E2335 S17G as well as [3 H]E1S, a model substrate to demonstrate microsomal activity of aryl- sulfatases, were not significantly different in microsomal fractions prepared from peritumor liver and sham-operated liver tissues (Table 2). Login to comment 228 ABCC3 p.Ser17Gly The desulfation activity toward E2335 S17G was low in relation to that for E1S. Login to comment 237 ABCC3 p.Ser17Gly Fig. 4. Radioelution chromatograms of products derived from incubation of E2335 S17G with Tris-HCl buffer (Ⅺ), and cytosolic (F) or microsomal (E) fractions. Login to comment 238 ABCC3 p.Ser17Gly The retention times of E23S17G (ϳ18 min, f) and 35 SO4 2- (ϳ3 min) were coincident with those obtained upon injection of the standards, E2335 S17G and 35 SO4 2- , into the HPLC column. Login to comment 239 ABCC3 p.Ser17Gly Desulfation of E2335 S17G in microsomes but not cytosol nor buffer, albeit of low activity, was observed. Login to comment 269 ABCC3 p.Ser17Gly Values of CLin in sham and tumor groups were 20 to 40 times the value of the blood flow TABLE 2 Desulfation activities or intrinsic clearances toward E2335 S17G and ͓3 H͔E1S (for confirmation of desulfation activity) in microsomal fractions, prepared from sham-operated and peritumor tissue at 4 weeks postinoculation Data are means Ϯ S.D. Desulfation Intrinsic Clearance Sham-Operated Liver Tissue Peritumor Tissue ␮l/s/mg microsomal protein E23S17G (CLint,desult,E23S17G) 0.16 Ϯ 0.04 0.12 Ϯ 0.02 E1S (CLint,desult, E1S) 7.88 Ϯ 0.76 8.09 Ϯ 1.29 Fig. 5. Login to comment 310 ABCC3 p.Ser17Gly The identity of the metabolite, E23S17G, was confirmed unequivocally with mass spectrometry and microsomal incubation studies with the radiolabeled E2335 S17G that was deconjugated by arylsulfatase C (also known as estrogen sulfatase) to reform E217G and 35 SO4 2- (Fig. 4), providing direct evidence of futile cycling between E23S17G and E217G. Login to comment