PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 8520630

Evidence for glucuronide (small molecule) sorting by human hepatic endoplasmic reticulum.

I D Waddell·K Robertson·A Burchell·R Hume·B Burchell
View original source ↗Export metadata ↓

Abstract

The entry of substrates into, and the export of glururonides from, the lumen of hepatic endoplasmic reticulum (ER) in vitro (sealed microsomes) has been measured using radioactivity-labelled materials and a rapid filtration assay. Analysis of liver microsomes from a jaundiced patient showed the accumulation of bilirubin glucuronides within the lumen of the ER. Further analysis of these hepatic microsomes revealed that newly synthesized 1-naphthol glucuronide could exit from the microsomes whereas bilirubin glucuronide was accumulated within the microsomes. These results suggest the existence of mechanisms for the sorting of small molecules, destined for export through bile canalicular or basolateral plasma membranes, by ER. Furthermore, these sorting processes may be regulated by specific transporters within the ER.

Explore related subjects

BilirubinCase-Control StudiesEndoplasmic ReticulumFiltrationGlucose-6-PhosphateGlucosephosphatesGlucuronatesGlucuronosyltransferaseHumansHyperbilirubinemiaInfant, NewbornMaleMicrosomes, LiverNaphtholsCase ReportsJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

I D Waddell, K Robertson, A Burchell, R Hume, B Burchell. Evidence for glucuronide (small molecule) sorting by human hepatic endoplasmic reticulum.. https://doi.org/10.3109/09687689509072429

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Partial hepatectomy as first-line treatment for patients with hepatocellular carcinoma.

BACKGROUND: Partial hepatectomy (PH) and liver transplantation (LT) compete as first-line treatment for hepatocellular carcinoma (HCC). A prospectively collected database was retrospectively reviewed to establish when PH can compete with LT. METHODS: Between 1991 and 2002, PH was performed in 131 cases of HCC (Child-Pugh A-B, technically resectable tumor without metastases). To ascertain patient survival after PH, we compared this series with a group of 40 HCC patients (G1-G2 HCC with no gross vascular invasion or metastasis) enlisted for liver transplantation during the same period. RESULTS: The 1-, 3-, and 5-year intention-to-treat survival rates were 75%, 52%, and 31% for resection and 89%, 71%, and 63% for transplantation. Two tumor-related variables (gross vascular invasion and histological grade) and three liver function parameters (Child-Pugh score, bilirubin, Okuda stage) proved to be independent predictors of survival after resection, whereas nodule size and number, and Milan criteria did not. The 5-year survival of the best candidates for resection (favorable tumor biology with very well preserved liver function, n = 52) was 58%. On a descriptive basis alone, this result did not differ significantly from the outcome in LT patients. PH patients with a poorly differentiated tumor and/or gross vascular invasion (n = 28) had the worst outcome, irrespective of their liver function parameters. CONCLUSIONS: For technically resectable tumors without aggressive features (G3 or macroscopic vascular invasion), PH can only compete with LT, in terms of long-term survival, when patients with a well-preserved liver function are selected.

Bilirubin↗
PubMed2007

Solvent partition of 14C-unconjugated bilirubin to remove labeled polar contaminants.

Polar derivatives contaminating unconjugated bilirubin (UCB) are customarily extracted with weak alkali. As UCB degrades rapidly at alkaline pH, regeneration of polar derivatives may limit purification. This problem is especially important when trying to eliminate radiolabeled contaminants from 14C-UCB. As polar derivatives of UCB should have a much greater aqueous to CHCl3 partition ratio (PR) than UCB even at neutral pH, where degradation of UCB is minimal, 14C-UCB in CHCl3 was serially extracted with an aqueous buffer at pH 7.0 to determine whether labeled derivatives could be preferentially removed. A single extraction of customarily purified 14C-UCB removed 0.18+/-0.06% of the radioactivity as labeled derivatives. Subsequent serial extractions yielded a stable, 67% lower 14C-PR with only 0.03% of radioactivity as labeled derivatives. Reverse-phase high-performance liquid chromatography (HPLC) of phases from later extractions revealed, however, that up to 1.1% of the disintegration per minute (dpm) in CHCl3 phases and up to 50% in aqueous phases were polar impurities. HPLC of partition phases spiked with purified 14C-UCB revealed that these impurities derived from incomplete extraction of the least polar impurities and their regeneration during HPLC. In the dark under argon, 14C-UCB in CHCl3or dimethyl sulfoxide (DMSO) solution degraded very slowly to polar derivatives. Extraction of impurities from a solution of 14C-UCB in CHCl3 is best done using pH 7.0 buffer, with removal of over 80% of the labeled contaminants remaining after customary purification by alkaline extraction.

Bilirubin↗