Free hemoglobin in the plasma is bound by a molecule called haptoglobin and gets recycled, which is why a low haptoglobin level is a sign of intravascular hemolysis.

血浆游离血红蛋白与结合珠蛋白结合，并被循环利用，这也是为何低结合珠蛋白水平是血管内溶血的标志之一。