Effects of hyperthermia pretreatment on expression of heme oxygenase-1 and nitric oxide synthase in rats subjected to experimental anaphylactic shock.

Previous studies have shown that hyperthermia pretreatment results in an attenuation of increased vascular leakage in rats subjected to experimental anaphylactic shock. It is known that both nitric oxide synthase (NOS) and heme oxygenase-1 (HO-1) play a role in the maintenance of microvascular integrity. In the study, we investigated the effect of hyperthermia pretreatment on mRNA expression of endothelial NOS (eNOS), inducible NOS (iNOS), and HO-1 in heated or nonheated rats subjected to anaphylactic shock using a semi-quantitative RT-PCR. Protein contents of eNOS and HO-1 in tissue were also assayed. Plasma nitrite and nitrate before and after induction of anaphylactic shock were quantified using a NO analyzer. The heated, anaphylactic rats showed a significant increase of HO-1 mRNA expression in heart as compared to both non-heated, anaphylactic and control rats. HO-1 protein contents in both heart and lung tissues in the heated, anaphylactic rats were significantly higher than both non-heated, anaphylactic and control rats. Protein contents of eNOS in various tissues appeared to be the same among groups. No significant change of iNOS mRNA expression was detected among groups. Plasma nitrite and nitrate before and after anaphylactic treatment appeared to be the same among groups. These data suggest that reduction of anaphylactic hypotension by hyperthermia pretreatment in rats subjected to anaphylactic shock may be resulted from over-expression of HO-1 rather than NOS in various tissues.