Myocardial and lung injuries induced by hydrogen sulfide and the effectiveness of oxygen therapy in rats

To study myocardial and lung injuries initiated by hydrogen sulfide, and evaluate the role and effectiveness of normobaric and hyperbaric oxygen (HBO) treatment in rats.

One hundred healthy male Wistar rats were randomly divided into five groups: A: Normal control group (no H2S); B: H2S-exposed group; C: H2S+33% oxygen treatment group; D: H2S+50% oxygen treatment group; E: H2S+HBO group. The rats in groups C, D and E were exposed to H2S in an exposure chamber (1 m3) and were made to inhale 300 ppm hydrogen sulfide for 60 min, and then they were subjected to normobaric or HBO therapy. Normobaric oxygen was at concentrations of 33% or 50%, HBO was for 100 min including compression and decompression; the rats in group A inhaled air under the same conditions. Blood was sampled immediately after the experiment for analysis of arterial blood gases, myocardial enzymes and cardiac troponin I. Lung was rapidly removed to be made into tissue homogenates and then cytochrome c oxidase activity was measured; myocardial and lung ultrastructural changes were observed by electron microscopy.

Arterial blood gases: partial pressure of O2 (mmHg) (Group A, 97.6 ± 8.38; B, 76.5 ± 6.95*; C, 83.2 ± 2.66*; D, 86.20 ± 10.75*; E, 93.50 ± 4.97: *p < 0.01 compared to group A) was significantly lower than that in group in all but HBO rats. For myocardial enzymes and cardiac troponin I every parameter in groups B and C was significantly higher than that in group A (p<0.01),with no difference in D and E. Cytochrome c oxidase activity (u/mg) of lung tissue was reduced compared to group A after all treatments (A, 1.76 ± 0.02; B, 0.36 ± 0.04; C, 0.50 ± 0.12; D, 0.56 ± 0.07; E, 0.68 ± 0.05 (A vs. B p < 0.01; B vs. C,D,E p < 0.05 or p < 0.01), with a graded effect of oxygen dose in C, D and E. Pathological changes: (1) Myocardium - Mitochondrial swelling and autolysis with blurred or broken cristae was observed in the myocardium of H2S-exposed group; in group E, mitochondrial structure was basically normal, and clear cristae were found. (2) Lung tissue - In H2S-exposed group, alveolar epithelial cells disappeared, vacuolization of the organelle occurred, nuclear membrane was irregular and marginal condensation of heterochromatin was present; nucleus showed relatively normal morphology in group E, although some vacuoles still persisted within them.

HBO therapy can effectively improve arterial oxygen partial pressure, and significantly reduce myocardial damage, as well as potentially relieve lung injury in this model. Further work in humans appears warranted.