THE EFFECT OF LOW-POWER LASER-LIGHT AT DIFFERENT DOSES ON GASTRIC-MUCOSA SENSITIZED WITH METHYLENE-BLUE, HEMATOPORPHYRIN DERIVATIVE OR TOLUIDINE BLUE

Helicobacter pylori has been associated with peptic ulcers, gastric ca ncer and various other gastroduodenal pathologies. Conventional antibi otic treatment is not entirely satisfactory, whereas photodynamic ther apy (PDT) is a possible alternative. Although PDT has been shown to be effective in killing helicobacter on native gastric mucosa, the succe ss of the technique will depend upon the mucosa underlying the bacteri a remaining unharmed. This study examined the effect of increasing dos es of low-power laser light on rat gastric mucosa, sensitized with eit her methylene blue (NIB), haematoporphyrin derivative (HpD) or toluidi ne blue (TBO), No damage was detectable with any of the photosensitize rs when a light dose of 250 J cm(-2) was used, Mucosal damage was seen consistently with TBO (1 mg ml(-1)) and a light dose of 500 J cm(-2). The same light dose of 500 J cm(-2) using MB caused inconsistent dama ge to the mucosa, whereas HpD had no effect even with the highest dose of laser light (500 J cm(-2)). As the energy doses required to kill b acteria (50 and 200 J cm(-2) for MB and TBO, respectively) are well be low the levels shown to damage normal gastric mucosa, PDT for H. pylor i should not be harmful to the underlying epithelium.