Objective: To investigate the mRNA and protein expressions of soluble guanylate cyclase (sGC) and its enzyme activity in pulmonary hypertension rat model which was reproduced by hypoxia and hypercapnia.
Methods: Male Sprague-Dawley rats were randomly divided into hypoxic and hypercapnic group (HH group) and control group (C group). The protein expressions of sGC alpha(1) and sGC beta(1) subunits in medial and small pulmonary arteries was measured by immunohistochemistry method with a polycolonal antibody. The mRNA expression of sGC alpha(1) subunit of lung tissue was detected by in situ hybridization using sGC oligonuclear probe. Basal sGC enzyme activity and sodium nitroprusside (SNP)-stimulated sGC activity in lung homogenates were assayed with enzyme kinetic analysis.
Results: The mean pulmonary artery pressure (mPAP), the ratio of right ventricle/left ventricle + septum [RV/(LV + S)] and the ratio of right ventricle/body weight (RV/BW) were significantly higher in HH group than those in C group. The protein expressions of sGC alpha(1) and sGC beta(1) subunits and mRNA expressions of sGC alpha(1) subunit were significantly decreased in the small and medium pulmonary arteries in HH group as compared with those in C group (P < 0.01). Basal sGC enzyme activity in HH group (32.03 +/- 7.17 pmol cGMP synthesized.mg protein(-1).min(-1)) was significantly lower than that in C group (114.76 +/- 18.37 pmol cGMP synthesized.mg protein(-1).min(-1), P < 0.01). The SNP significantly increased the sGC enzyme activity but the SNP-stimulated sGC enzyme activity of lung homogenates in HH group was significantly lower than that in C group (P < 0.01).
Conclusions: The mRNA and protein expressions of sGC subunits and their enzyme activities in lung tissue of pulmonary hypertension rat model were reduced.