Human MRP3 Vesicle Kit (HEK293 derived) | 100 Reactions

When should MRP3 be included in a transporter profiling panel?

MRP3 is particularly valuable in three scenarios: (1) compounds with extensive hepatic glucuronidation, where you need to understand the sinusoidal export route for glucuronide metabolites and their systemic exposure; (2) BSEP inhibitors, where cholestatic bile acid overflow through MRP3 is the primary compensatory mechanism and must be characterised to assess net hepatotoxic risk; and (3) compounds with significant enterohepatic circulation, where intestinal MRP3 activity affects the mucosal-to-serosal transport of phase II metabolites. MRP3 is also included when the compound structurally resembles known MRP3 substrates such as methotrexate, etoposide, or monoanionic bile salts.

What is the relationship between MRP3 and BSEP in cholestasis DDI studies?

BSEP (ABCB11) and MRP3 (ABCC3) serve complementary roles in hepatic bile acid handling. Under normal conditions, BSEP mediates canalicular secretion of conjugated bile acids into bile. When BSEP function is impaired — by drug inhibition or genetic variation — bile acids accumulate intracellularly and drive upregulation of MRP3 at the basolateral membrane, redirecting bile acid efflux into sinusoidal blood as a compensatory overflow mechanism. In BSEP DDI studies, characterising MRP3 activity alongside BSEP is important: a compound that strongly inhibits BSEP while also inhibiting MRP3 removes both export routes simultaneously, substantially increasing hepatocyte bile acid accumulation and cholestatic injury risk. Running both assays in parallel gives a more complete picture of net hepatic bile acid flux.

What substrates and probe substrates are used in MRP3 vesicular transport assays?

Well-characterised MRP3 (ABCC3) substrates for vesicular transport assays include estradiol-17β-D-glucuronide (E217βG) — the most commonly used radiolabelled probe substrate — as well as taurolithocholate-3-sulfate (TLCS), methotrexate, etoposide glucuronide, and monoanionic bile acids such as glycocholate. For inhibition studies, reference inhibitors include MK571 (pan-MRP inhibitor) and probenecid. The Cell4Pharma kit protocol provides lot-specific recommendations for probe substrate concentration and incubation conditions to achieve the guaranteed ATP/AMP ratio of >5.

How does MRP3 differ from MRP2, and why are both relevant in hepatic DDI panels?

MRP2 (ABCC2) and MRP3 (ABCC3) share significant substrate overlap — both transport glucuronide conjugates and bile salts — but are localised on opposite faces of the hepatocyte. MRP2 sits at the canalicular (apical) membrane and drives substrate secretion into bile, while MRP3 sits at the basolateral (sinusoidal) membrane and redirects substrates into the portal circulation. This opposing polarity means the two transporters compete for the same hepatocellular substrate pool and together determine whether a glucuronide conjugate exits via bile or systemic blood. For DDI risk assessment of compounds that undergo hepatic glucuronidation, characterising both MRP2-mediated biliary excretion and MRP3-mediated sinusoidal efflux provides the complete picture of hepatic clearance routes and metabolite systemic exposure.

What documentation is supplied with the Human MRP3 Vesicle Kit?

Every kit shipment includes a lot-specific QC report confirming the ATP/AMP transport ratio (>5) and vesicle preparation parameters, and a data sheet with recommended assay conditions, probe substrates, and reference inhibitor concentrations. All Cell4Pharma kits are manufactured under ISO 9001 and ISO 13485 certified quality systems. Batch reservation for up to 36 months is available on request — particularly important for multi-transporter DDI panels where lot-to-lot consistency between the MRP3 kit and matched Control Vesicle Kit must be maintained across the full study duration.