The primary excretion route for protoporphyrin (PROTO), uroporphyrin (URO), and coproporphyrin (COPRO) are

The primary excretion route for protoporphyrin (PROTO), uroporphyrin (URO), and coproporphyrin (COPRO) are

• A. URO is excreted primarily in the urine, PROTO in the feces, and COPRO in either.
• B. URO is excreted primarily in the feces, PROTO in the urine, and COPRO in either.
• C. URO is excreted primarily in the urine, PROTO and COPRO in the feces.
• D. URO is excreted primarily in the feces, PROTO and COPRO in urine.

Answer: (C)

Porphyrin excretion is driven by solubility: water-soluble compounds are cleared by the kidneys into urine, while lipid-soluble ones are excreted via bile into the feces. Uroporphyrin has multiple carboxyl groups that make it highly water-soluble, so it is eliminated primarily in urine. Protoporphyrin and coproporphyrin are less water-soluble and more lipophilic, so they are mainly excreted through the biliary system into the intestines and end up in feces. This pattern—URO in urine, PROTO and COPRO in feces—reflects their differing solubilities and routes of elimination.

Porphyrin excretion is driven by solubility: water-soluble compounds are cleared by the kidneys into urine, while lipid-soluble ones are excreted via bile into the feces. Uroporphyrin has multiple carboxyl groups that make it highly water-soluble, so it is eliminated primarily in urine. Protoporphyrin and coproporphyrin are less water-soluble and more lipophilic, so they are mainly excreted through the biliary system into the intestines and end up in feces. This pattern—URO in urine, PROTO and COPRO in feces—reflects their differing solubilities and routes of elimination.