ABCC4 and cholestasis: Because induction of MRP-4 represents an adaptive response to bile duct obstruction and protects the liver from accumulation of toxic bile acids during cholestasis by facilitating their efflux into blood for ultimate renal excretion, and MRP-4-knockout mice are sensitised to liver injury induced by BDL [4], regulation of this basolateral transporter exerts an essential role in orchestrating the adaptive changes under conditions of impaired bile flow due canalicular obstruction/destruction [2], [5]–[7].