ABCB11 and cholestasis: It is also known that low physiological MRP4 (ABCC4) expression levels (Deeley et al. 2006) markedly increase during cholestasis as a part of an adaptative response that consists in the basolateral efflux of BAs to compensate BSEP and MRP2 dysfunctions (Jetter and Kullak-Ublick 2020).