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Quantification of drug transport function across the multiple resistance-associated protein 2 (Mrp2) in rat livers.

Bonnaventure P, Pastor CM - Int J Mol Sci (2014)

Bottom Line: The aim of the study is then to measure these concentrations and define parameters to quantify the canalicular transport of drugs through the multiple resistance associated-protein 2 (Mrp2) in entire rat livers.In contrast, the ratio was when BOPTA was not excreted in bile in hepatocytes lacking Mrp2.The canalicular concentration ratio is more informative than bile excretion rates because it is independent of time, bile flows, and concentrations perfused in portal veins.

View Article: PubMed Central - PubMed

Affiliation: Universitaires de Genève, Geneva 1205, Switzerland. pierre.bonnaventure@unige.ch.

ABSTRACT
To understand the transport function of drugs across the canalicular membrane of hepatocytes, it would be important to measure concentrations in hepatocytes and bile. However, these concentration gradients are rarely provided. The aim of the study is then to measure these concentrations and define parameters to quantify the canalicular transport of drugs through the multiple resistance associated-protein 2 (Mrp2) in entire rat livers. Besides drug bile excretion rates, we measured additional parameters to better define transport function across Mrp2: (1) Concentration gradients between hepatocyte and bile concentrations over time; and (2) a unique parameter (canalicular concentration ratio) that represents the slope of the non-linear regression curve between hepatocyte and bile concentrations. This information was obtained in isolated rat livers perfused with gadobenate dimeglumine (BOPTA) and mebrofenin (MEB), two hepatobiliary drugs used in clinical liver imaging. Interestingly, despite different transport characteristics including excretion rates into bile and hepatocyte clearance into bile, BOPTA and MEB have a similar canalicular concentration ratio. In contrast, the ratio was when BOPTA was not excreted in bile in hepatocytes lacking Mrp2. The canalicular concentration ratio is more informative than bile excretion rates because it is independent of time, bile flows, and concentrations perfused in portal veins. It would be interesting to apply such information in human liver imaging where hepatobiliary compounds are increasingly investigated.

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(A) Diethylenetriaminepentaacetic acid (DTPA), gadobenate dimeglumine (BOPTA), and mebrofenin (MEB) solutions perfused over time. DTPA is an extracellular contrast agent used in liver imaging that distributes into sinusoids and intersititum while BOPTA and MEB also enter into hepatocytes following extracellular distribution. DTPA was labelled either with 153GdCl3 or 99mTc while BOPTA was labelled with 153GdCl3 and MEB with 99mTc. 153Gd-DTPA and 153Gd-BOPTA were diluted in Krebs-henseleit bicarbonate (KHB) solution to obtain a 200-µM concentration. 99mTc-DTPA and 99mTc-MEB were diluted in KHB solution to obtain a 64-µM concentration. Three groups of rat livers were perfused: (1) Livers isolated from normal rats and perfused with 200 µM DTPA and 200 µM BOPTA (BOPTA group, black circles, n = 5); (2) livers isolated from rats lacking Mrp2 and perfused with 200 µM DTPA and 200 µM BOPTA (BOPTA-TR group, green circles, n = 3); and (3) livers isolated from normal rats and perfused with 64 µM DTPA and 64 µM MEB (blue circles, n = 5); and (B) Bile flow rates (µL/min/g of liver) in the three experimental groups over time (min).
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ijms-16-00135-f001: (A) Diethylenetriaminepentaacetic acid (DTPA), gadobenate dimeglumine (BOPTA), and mebrofenin (MEB) solutions perfused over time. DTPA is an extracellular contrast agent used in liver imaging that distributes into sinusoids and intersititum while BOPTA and MEB also enter into hepatocytes following extracellular distribution. DTPA was labelled either with 153GdCl3 or 99mTc while BOPTA was labelled with 153GdCl3 and MEB with 99mTc. 153Gd-DTPA and 153Gd-BOPTA were diluted in Krebs-henseleit bicarbonate (KHB) solution to obtain a 200-µM concentration. 99mTc-DTPA and 99mTc-MEB were diluted in KHB solution to obtain a 64-µM concentration. Three groups of rat livers were perfused: (1) Livers isolated from normal rats and perfused with 200 µM DTPA and 200 µM BOPTA (BOPTA group, black circles, n = 5); (2) livers isolated from rats lacking Mrp2 and perfused with 200 µM DTPA and 200 µM BOPTA (BOPTA-TR group, green circles, n = 3); and (3) livers isolated from normal rats and perfused with 64 µM DTPA and 64 µM MEB (blue circles, n = 5); and (B) Bile flow rates (µL/min/g of liver) in the three experimental groups over time (min).

Mentions: Solutions and drugs perfused in the livers over time are illustrated in Figure 1A. Before 45 min, bile flow rates remained steady in the three groups. However, bile flow rates were significantly decreased in the group of livers lacking Mrp2 (Figure 1B). During drug perfusion, bile flow rates significantly increased in BOPTA group (p < 0.0001) but remained unchanged in the two other groups. During the rinse period (Krebs-henseleit bicarbonate (KHB) perfusion), bile flow rates returned to baseline values in the BOPTA group while bile flow rates slightly decreased at the end of the protocol in the MEB group.


Quantification of drug transport function across the multiple resistance-associated protein 2 (Mrp2) in rat livers.

Bonnaventure P, Pastor CM - Int J Mol Sci (2014)

(A) Diethylenetriaminepentaacetic acid (DTPA), gadobenate dimeglumine (BOPTA), and mebrofenin (MEB) solutions perfused over time. DTPA is an extracellular contrast agent used in liver imaging that distributes into sinusoids and intersititum while BOPTA and MEB also enter into hepatocytes following extracellular distribution. DTPA was labelled either with 153GdCl3 or 99mTc while BOPTA was labelled with 153GdCl3 and MEB with 99mTc. 153Gd-DTPA and 153Gd-BOPTA were diluted in Krebs-henseleit bicarbonate (KHB) solution to obtain a 200-µM concentration. 99mTc-DTPA and 99mTc-MEB were diluted in KHB solution to obtain a 64-µM concentration. Three groups of rat livers were perfused: (1) Livers isolated from normal rats and perfused with 200 µM DTPA and 200 µM BOPTA (BOPTA group, black circles, n = 5); (2) livers isolated from rats lacking Mrp2 and perfused with 200 µM DTPA and 200 µM BOPTA (BOPTA-TR group, green circles, n = 3); and (3) livers isolated from normal rats and perfused with 64 µM DTPA and 64 µM MEB (blue circles, n = 5); and (B) Bile flow rates (µL/min/g of liver) in the three experimental groups over time (min).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4307239&req=5

ijms-16-00135-f001: (A) Diethylenetriaminepentaacetic acid (DTPA), gadobenate dimeglumine (BOPTA), and mebrofenin (MEB) solutions perfused over time. DTPA is an extracellular contrast agent used in liver imaging that distributes into sinusoids and intersititum while BOPTA and MEB also enter into hepatocytes following extracellular distribution. DTPA was labelled either with 153GdCl3 or 99mTc while BOPTA was labelled with 153GdCl3 and MEB with 99mTc. 153Gd-DTPA and 153Gd-BOPTA were diluted in Krebs-henseleit bicarbonate (KHB) solution to obtain a 200-µM concentration. 99mTc-DTPA and 99mTc-MEB were diluted in KHB solution to obtain a 64-µM concentration. Three groups of rat livers were perfused: (1) Livers isolated from normal rats and perfused with 200 µM DTPA and 200 µM BOPTA (BOPTA group, black circles, n = 5); (2) livers isolated from rats lacking Mrp2 and perfused with 200 µM DTPA and 200 µM BOPTA (BOPTA-TR group, green circles, n = 3); and (3) livers isolated from normal rats and perfused with 64 µM DTPA and 64 µM MEB (blue circles, n = 5); and (B) Bile flow rates (µL/min/g of liver) in the three experimental groups over time (min).
Mentions: Solutions and drugs perfused in the livers over time are illustrated in Figure 1A. Before 45 min, bile flow rates remained steady in the three groups. However, bile flow rates were significantly decreased in the group of livers lacking Mrp2 (Figure 1B). During drug perfusion, bile flow rates significantly increased in BOPTA group (p < 0.0001) but remained unchanged in the two other groups. During the rinse period (Krebs-henseleit bicarbonate (KHB) perfusion), bile flow rates returned to baseline values in the BOPTA group while bile flow rates slightly decreased at the end of the protocol in the MEB group.

Bottom Line: The aim of the study is then to measure these concentrations and define parameters to quantify the canalicular transport of drugs through the multiple resistance associated-protein 2 (Mrp2) in entire rat livers.In contrast, the ratio was when BOPTA was not excreted in bile in hepatocytes lacking Mrp2.The canalicular concentration ratio is more informative than bile excretion rates because it is independent of time, bile flows, and concentrations perfused in portal veins.

View Article: PubMed Central - PubMed

Affiliation: Universitaires de Genève, Geneva 1205, Switzerland. pierre.bonnaventure@unige.ch.

ABSTRACT
To understand the transport function of drugs across the canalicular membrane of hepatocytes, it would be important to measure concentrations in hepatocytes and bile. However, these concentration gradients are rarely provided. The aim of the study is then to measure these concentrations and define parameters to quantify the canalicular transport of drugs through the multiple resistance associated-protein 2 (Mrp2) in entire rat livers. Besides drug bile excretion rates, we measured additional parameters to better define transport function across Mrp2: (1) Concentration gradients between hepatocyte and bile concentrations over time; and (2) a unique parameter (canalicular concentration ratio) that represents the slope of the non-linear regression curve between hepatocyte and bile concentrations. This information was obtained in isolated rat livers perfused with gadobenate dimeglumine (BOPTA) and mebrofenin (MEB), two hepatobiliary drugs used in clinical liver imaging. Interestingly, despite different transport characteristics including excretion rates into bile and hepatocyte clearance into bile, BOPTA and MEB have a similar canalicular concentration ratio. In contrast, the ratio was when BOPTA was not excreted in bile in hepatocytes lacking Mrp2. The canalicular concentration ratio is more informative than bile excretion rates because it is independent of time, bile flows, and concentrations perfused in portal veins. It would be interesting to apply such information in human liver imaging where hepatobiliary compounds are increasingly investigated.

Show MeSH
Related in: MedlinePlus