Liver Perfusion Modifies Gd-DTPA and Gd-BOPTA Hepatocyte Concentrations Through Transfer Clearances Across Sinusoidal Membranes.

Abstract

Gadobenate dimeglumine (Gd-BOPTA) is a commercialised hepatobiliary contrast agent used during liver magnetic resonance imaging (MRI) to detect liver diseases. It enters into human hepatocytes through organic anion transporting polypeptides (OATP1B1/B3) and crosses the canalicular transporter multiple resistance-associated protein 2 (MRP2) to be excreted into bile canaliculi. Gd-BOPTA can return to sinusoids via the sinusoidal transporters MRP3/MRP4. Hepatocyte concentrations of Gd-BOPTA depend on three clearances: the sinusoidal clearance or volume of sinusoidal blood cleared of drugs per unit of time and two hepatocyte clearances (into bile canaliculi or back to sinusoids) or volume of hepatocytes cleared of drugs per unit of time in the respective liver compartments. The present study investigates whether changing liver blood flow modifies hepatocyte concentrations when plasma concentrations do not change. We perfused normal rat livers at various portal flow rates (24, 30, and 36ml/min) with 200µM Gd-BOPTA and measured sinusoidal clearances, hepatocyte clearances, and hepatocyte concentrations of Gd-BOPTA. We showed that varying portal flow rates changes the sinusoidal clearance of Gd-BOPTA despite its low extraction ratio. Portal flow rates do not modify Gd-BOPTA clearance from hepatocytes into bile canaliculi but can change hepatocyte clearance back to sinusoids. At a given perfused concentration, portal flow rates modify Gd-BOPTA hepatocyte concentrations, a result important to consider when interpreting liver imaging.