Analysis of bilirubin fraction in the bile for early diagnosis of acute rejection in living related liver transplantation

An assay for separating and quantifying four bilirubin fractions in untreated human serum using isocratic high-performance liquid chromatography

BACKGROUND

The quantification of serum bilirubin fractions has been widely performed with both the diazo-method and an enzymatic method; however, the accuracy of these methods has not been evaluated because quantitative fractional high-performance liquid chromatography (HPLC) reference methods have yet to be established.

METHODS

Samples were analyzed using HPLC and Shodex Asahipak GS-320HQ columns. Human serum was subjected to HPLC using direct injection, then eluted with acetonitrile: 0.3 mol/l phosphate buffer (pH 6.5) containing 1% Brij 35 and 0.08% sodium ascorbate (30:70, v/v).

RESULTS

Serum bilirubin was separated into 4 fractions; retention times of 9.24, 19.92, 24.07, 35.75 min were identified as delta bilirubin, bilirubin diglucuronide, bilirubin monoglucuronide, and unconjugated bilirubin, respectively. Mean recovery was 93.0%-99.2%. Total precision of peak retention time, height and area exhibited <4.26% variation. Detection range was 3.1 to 348 mg/l. Hemoglobin (6 g/l) and immunoglobins produced a small positive interference. beta-carotene (20 mg/l), vitamin-B2 (370 microg/l) and B(12) (9.5 microg/l) did not interfere with this analysis. Results (n=30) with this method were closely correlated to those by Adachi's HPLC method as r=0.9941 to 0.9960, slope=0.88 to 1.27, intercept=-3.2 to +4.9, for each fraction.

CONCLUSIONS

Since this method was a precise quantitative HPLC method for serum bilirubin fractionation, it might be used to evaluate the accuracy and the characteristics of various routine methods for bilirubin measurement.

Significance of altered bilirubin subfractions in bile following hepatectomy

BACKGROUND

Hyperbilirubinemia occurs as a sign of hepatic failure after hepatectomy. The pathogenesis of this event has not been elucidated. In cases complicated with postoperative infection, hyperbilirubinemia is prolonged and the composition of bilirubin subfractions in bile changes markedly. A reduction in the proportion of bilirubin diglucuronide (BDG) is especially notable. This study was aimed at clarifying the relationship between infection and biliary bilirubin subfractions, with a view to shedding light on the mechanisms of change.

MATERIALS AND METHODS

Rats underwent either laparotomy or partial hepatectomy (Hx). Daily intraperitoneal injections of lipopolysaccharide (LPS) or natural saline were administered for 3 days following surgery. Total serum bilirubin levels and proportions of BDG and bilirubin in bile were measured until Day 5 after the operation. Hepatic levels of UDP-glucuronic acid (UDP-GA), UDP-glucose, NAD(+), and total adenine nucleotides (TAN) and activities of UDP-glucuronyltransferase (UDP-GT) and UDP-glucose dehydrogenase were measured on Day 4.

RESULTS

In hepatectomized rats treated with LPS (Hx-LPS), total serum bilirubin levels were elevated, biliary bilirubin levels were decreased, and the proportion of biliary BDG was decreased on Day 4. Hepatic levels of UDP-GA, NAD(+), and TAN and activities of UDP-GT in Hx-LPS were reduced. In all groups tested, a significant linear correlation between BDG and UDP-GA and between UDP-GA and NAD(+) was found.

CONCLUSIONS

The reduction of UDP-GA might be effected by reduced hepatic levels of NAD(+) in endotoxemia following hepatectomy. It is therefore suggested that alterations in biliary bilirubin subfractions might accurately reflect the energy state of the remnant liver following hepatectomy.