5-aminolevulinic acid-induced accumulation of protoporphyrin IX in rat brain tissue

Abstract

The aim of the study was to compare the level of accumulation of protoporphyrin IX (ППIX) in the brain of rats in normal conditions and in experimental C6 glioma.

Materials and methods. In an experiment on 15 rats, one group of animals (n=5) was intracranially implanted with rat glioma of the C6 line. 14 days after tumor implantation, the animals were injected into the lateral vein of the tail with a photosensitizer — a preparation of 5-aminolevulinic acid (5-ALA) Alasens at a dose of 100 mg / kg. Another group consisted of 5 intact rats, which were also injected with Alasens. The rats were euthanized 4–5 hours after the injection of the photosensitizer, and fluorescent metabolic navigation was performed with illumination of the brain with light with wavelengths of 417 and 435 nm. For objectification, fluorescence biospectroscopy was performed. Similar manipulations were performed with animals of another group (n=5) — intact rats that did not receive Alasens.

Results. In contrast to humans, in rats, the 5-ALA metabolite — PPIX accumulates in healthy brain tissue, while the fluorescence intensity does not differ from that visualized in the tumor area. It was also noted that the light of the blue spectrum promotes weak fluorescence of the white matter of the rat brain in the absence of exogenous 5-ALA, which can potentially be explained by the activation of endogenous PPIX or other fluorophores.

Conclusion. After the administration of Alasens (5-ALA preparation), the accumulation of PPIX by the rat brain tissue occurs not only by malignant cells, but also by normal brain tissue without signs of malignancy or other pathological changes. A more thorough study of this phenomenon is required, since significant differences in the metabolism of 5-ALA in humans and laboratory animals will call into question the correctness of translation of experimental results into clinical practice.