Photodynamic therapy in normal pig stomach: protective effect of octreotide

Many factors, such as oxygen and vasculature, are involved in the cytotoxic effect of photodynamic therapy (PDT). It is known that somatostatin and its analog octreotide decrease the splanchnic blood flow and have multiple inhibitory effects in different functions of the peptic system. The aim of this experimental study was to assess the effect of octreotide administration on PDT outcome in normal pig stomach.

28 healthy pigs, randomly assigned to two groups, A and B, were studied. Pigs in both groups were sensitized with 0.3 mg/kg intravenous meta-tetra (hydroxyphenyl) chlorin (m-THPC), and 48 hours later light of wavelength 650 nm was delivered from a 50-mW diode laser for 300 s (energy fluence 15 J/cm (2)) through a gastroscope to the gastric mucosa. Group A underwent PDT without octreotide and group B had PDT with administration of octreotide. At 72 h after light delivery, all the animals were sacrificed for macroscopic and histological evaluation of the irradiated site.

The macroscopic images and the histology of the stomach PDT lesions (inflammation, ulceration, necrosis) showed significantly less severity in the group of animals with octreotide injection (group B). In this group, full-thickness necrosis was observed in 28.5 %, compared with over 71.4 % in group A; this was statistically significant ( P < 0.05).

Octreotide may have a modulating effect on m-TPHC PDT in normal gastric tissue in pigs, probably due to alterations of hemodynamics in the stomach and to suppression of the inflammatory process.