ObjectiveTo study the influence of hemin on blood pressure of intermittent hypoxic rats and investigate the mechanism of hypertension caused by intermittent hypoxia.MethodsTwenty-four male SD rats were randomly divided into a hemin group, an intermittent hypoxia group (IH group) and a normal group. Thirty minutes after intraperitoneal injection of hemin, the rats in the hemin group were exposed to intermittent normobaric hypoxic environment (8 h/d). The rats in the IH group were intraperitoneal injected with normal sodium and then exposed to the same environment (8 h/d). The rats in the normal group were intraperitoneal injected with normal sodium and placed in the glass box. The three groups were bred in the same condition. Thirty-five days later, the mean carotid artery pressure (mCAP) of the rats was measured and their plasma carbon monoxide (CO) level was measured by Chalmer’s method. Reverse transcription polymerase chain reaction was performed to detect the levels of heme oxygenase-1 (HO-1) mRNA expression in lung, liver, spleen, kidney and other organs. The expression of HO-1 protein in the organs was detected by immunohistochemistry.ResultsThe mCAP in the IH group was significantly higher than the hemin group and the normal group (P<0.05), and was higher in the hemin group than the normal group (P<0.05). The concentration of plasma CO in the hemin group was higher than the IH group and the normal group (P<0.05). There was no significant difference in plasma CO between the IH group and the normal group (P>0.05). The expression of HO-1 mRNA of lung, liver, spleen and kidney in the hemin group and the IH group was higher than the normal group (P<0.05), and was higher in the hemin group than the IH group (P<0.05). The relationship between mCAP and HO-1 mRNA showed a curvilinear trend. The quadratic curve fitting equation was Y=39.715+446.640X-334.353X2.ConclusionsIntermittent hypoxia can cause hypertension in rats. The HO-1 expression is increased in hypoxic rats, but the plasma CO does not increase significantly. As an inducer of HO-1, hemin can increase the expression of HO-1 and CO in hypoxic rats, then lower their blood pressure to some extent.