Free hemoglobin is cleared from the plasma of the rabbit significantly faster than the hemoglobin-haptoglobin complex. This difference can be partly attributed to the fact that free hemoglobin passes readily through the renal glomerulus whereas the complex is too large to pass through. The liver is the principal organ of hemoglobin-haptoglobin catabolism.
In the nephrectomized rabbit hemoglobin is cleared from the plasma significantly faster than the hemoglobin-haptoglobin complex, and both molecules are catabolized in the same organs, principally the liver. The iron of both hemoglobin and the complex is rapidly recirculated to the bone marrow via transferrin.