Meso-tetra-(4-sulfonatophenyl)-porphine of low neurotoxicity.

The acute toxicity of specially purified meso-tetra-(4-sulfonatophenyl)-porphine (TPPS4) was measured in mice DBA/2 and Wistar rats after i.v. administration of the dye dissolved in saline solution. LD50 of our preparation was 352.5 mg/kg for mice and 574.9 mg/kg for rats. Motor nerve conduction velocity was measured in rats and rabbits in ether anesthesia N. ischiadicus and n. tibialis were stimulated by surface electrodes and M response was registered. No signs of neurotoxicity were found, even after application of 150 mg/kg b.w. of our TPPS4. Histologic evaluation was performed by routine method and standard electron microscopic procedure. Only minimal and sporadic axonal changes were found. The clinical application of low toxic TPPS4 was reconsidered.