In rotors syndrome there is defect in organic anion transport protein which is required for bilirubin uptake in liver. Then why there is predominant conjugated hyperbilirubinemia in it?
In a normal liver, a majority of bilirubin is conjugated by hepatocytes and secreted back into the blood. It is then reabsorbed in downstream hepatocytes by the OATP1B1 and OATP1B3 proteins. In Rotor syndrome, the OATP1B1 and OATP1B3 proteins are abnormally short; therefore, the bilirubin that is conjugated is hepatocytes is less efficiently removed from the body by the defective OATP1B1 and OATP1B3 proteins, causing a buildup of bilirubin in the blood and urine which results in jaundice and dark urine.