Bilirubin is transported from reticuloendothelial cells to the liver by?

Bilirubin, a breakdown product of heme from hemoglobin, is transported from reticuloendothelial cells—primarily in the spleen—through the bloodstream to the liver where it undergoes processing for excretion. The correct transport mechanism involves its binding to albumin, a major plasma protein that has a high affinity for bilirubin. This binding is crucial since bilirubin is poorly soluble in water and its transport in an unbound form could lead to toxic levels.

Albumin serves as a carrier, enabling bilirubin to traverse aqueous environments in the bloodstream. Once it reaches the liver, albumin facilitates the uptake of bilirubin by hepatocytes, where it can then be conjugated to glucuronic acid to form conjugated bilirubin (also known as direct bilirubin), which is water-soluble and can be excreted into bile.

While other options like bilirubin-binding globulin do exist, they do not play a significant role in the general transport of bilirubin in comparison to albumin. Similarly, haptoglobin and transferrin are primarily involved in the transport of hemoglobin and iron, respectively, and are not involved in the bilirubin transportation process. Thus, the primary and most relevant transporter of bilirubin from