Relation between Serum Protophorphyrin Concentrations and Pathohistological Findings in Tumor-bearing Dogs which were Orally Given 5-aminolevulinic Acid

Abstract

5-aminolevulinic acid (ALA), one of the natural amino acids found in animals and plants, is metabolized into a photosensitizer, protoporphyrin IX (PPIX) in vivo. In this study, ALA was administrated orally to tumor-bearing dogs, the relation between serum concentrations of PPIX and pathohistological findings was discussed, and the feasibility of judging whether or not the tumor was malignant was assessed. Using eight dogs with a malignant tumor and five dogs with a non-malignant tumor, ALA was administrated (30 mg/kg), the blood was sampled sequentially, and the concentrations of PPIX were measured. There were no significant differences in PPIX concentrations between the two groups. In the malignant group, however, PPIX concentrations 3 hrs after administration were significantly higher than those measured before administration (p<0.05) ; the sensitivity and specificity were 75% and 80%, respectively, when the PPIX concentrations were more than 5.5 pmol/l. From these results, the possibility of ALA being used as a tumor marker in small animal practice was suggested.