Abstract Objective To explore the change of heme substances in asthma and the relationship between heme substances and asthmatic attack. Methods Sixty guinea pigs were equally separated into 6 groups. Except for normal control group (NCG), asthmatic models were divided into 5 groups. Two of them were treated with the specific stimulator (hemin) and the inhibitor (Sn-PP)of HO -1 respectively, the other group received dexamethasone as a preventive measure, and the last were asthmatic and nature rescuing asthmatic groups (NRAG). In all the tested animals, the COHb and NO in blood, lung HO -1 activity, and lung cGMP were examined. The lung tissues were pathologically observed and stained immunohistochemically. Results In the asthmatic (AG) and heme stimulated groups (HG), the levels of the COHb, NO, lung HO -1 activity and cGMP were significantly increased compared with NCG ( t values were ① 5.69 in AG, 9.29 in HG, ② 6.28 , 10.19 , ③ 5.77 , 8.92 , ④ 9.74 , 6.96 , P < 0.01 , respectively). Lung HO -1 activities were (1449±426) pmol/mg. COHb in blood ( 7.43 ± 2.07 )%, NO in blood ( 90.9 ± 16.7 ) μmol/L, lung cGMP ( 1.96 ± 0.65 ) pmol/mg, and lung HO -1 protein expression ≥4 grade in hemin stimulated group respectively. Whereas, in the Sn-pp inhibited, dexamethasone and NSAG groups, they were markedly reduced compared with the asthmatic group ( P < 0.01 ). Conclusions In asthma, the increased NO, cGMP induced by NOS and sGC, and HO -1 protein suggest that heme substances catalyzed by HO are enhanced. These may be contributory to airway hyperresponsiveness.
