An experimental model for the study of porphyric neuropathy is presented. Injection of either tetraphenylporphinesulfonate (TPPS), hematoporphyrin derivative (HpD), or delta-aminolevulinic acid (ALA) into mice resulted in markedly decreased motor nerve conduction velocity (MNCV). The MNCV returned to normal within one week following the injection of large doses of A LA, and within three weeks following the injection of close to lethal doses of HpD. hut there was no recovery of nerve function within 60 days following injection of substantially smaller doses of TPPS. Ultrastructural examination of motor nerves at various times following TPPS injection revealed the gradual development of structural abnormalities. Ultrastructional examination of the same nerves after a single dose of either A LA or Hp D failed to demonstrate any abnormalities.
The present observations call for precaution as to the use of TPPS as photosensitizer in human cancer treatment.