cyclic-gmp and Edema--Cardiac

Most cardiac procedures involve the use of cardiopulmonary bypass (CPB), which pumps oxygenated blood to the body while the heart and lungs are isolated. CPB can cause profound alterations V in the homeostasis of physiological fluids, which often results in myocardial edema. In our study, we used sheep CPB model of in vivo and in vitro to assess the relationship between cGMP and AQP1 during CPB.. ODQ, a specific inhibitor of soluble guanylate cyclase (sGC), was used to treat the CPB animals or cardiomyocytes. Left ventricular function of each group was determined by pressure-volume system. Water content of myocardial tissue was assessed by dry-wet weight, and cardiomyocytes water permeability was also calculated. The concentration of cGMP was determined by Radioimmunoassay (RIA). mRNA and protein expression of AQP1 were detected by real-time PCR and western blot, respectively.. The relative expression level of AQP1 mRNA and protein at each time point (0, 6, 12, 24 or 48 h) after CPB was significantly increased (1.18-fold at 12 h, 1.77-fold at 24 h and 2.18-fold at 48h) compared with each sham group, the protein expression of AQP1 also showed a rising trend after CPB. The degree of myocardial edema (75.1% at 12 h, 79.3% at 24 h and 81.0% at 48h) increased following the CPB surgery. The mRNA expression level of AQP1 was significantly decreased by 39.7% (p<0.01) upon treatment with ODQ compared with the CPB-only group, and inhibition of cGMP pathway also can significantly decrease the degree of myocardial edema (84.7% in control group, while 75.2% in ODQ group) and improve cardiac function in sheep after CPB. Results of in vitro experiments showed the same changing trends as in vivo.. cGMP pathway controls water channels and then affects water intake during CPB through an AQP1-mediated pathway.

Topics: Animals; Aquaporin 1; Cardiopulmonary Bypass; Cyclic GMP; Edema, Cardiac; Female; Myocytes, Cardiac; Oxadiazoles; Quinoxalines; Sheep, Domestic

Ischaemia-reperfusion provokes barrier failure of the coronary microvasculature, impeding functional recovery of the heart during reperfusion. The aim of the present study was to investigate whether the stimulation of cGMP signalling by activation of soluble guanylyl cyclase (sGC) can reduce reperfusion-induced endothelial intercellular gap formation and to determine whether this is due to an influence on endothelial cytosolic Ca(2+) homeostasis during reperfusion.. Experiments were performed with cultured coronary endothelial monolayers and isolated saline-perfused rat hearts. HMR1766 (1 micromol/L) or DEAnonoate (0.5 micromol/L) were used to activate sGC. After exposure to simulated ischaemic conditions, reperfusion of endothelial cells led to a pronounced increase in cytosolic calcium levels and intercellular gaps. Stimulation of cGMP signalling during reperfusion increased Ca(2+) sequestration in the endoplasmic reticulum (ER) and attenuated the reperfusion-induced increase in cytosolic [Ca(2+)]. Phosphorylation of phospholamban was also increased, indicating a de-inhibition of the ER Ca(2+) pump (SERCA). Reperfusion-induced intercellular gap formation was reduced. Reduction of myosin light chain phosphorylation indicated inactivation of the endothelial contractile machinery. Effects on cytsolic Ca(2+) and gaps were abrogated by inhibition of cGMP-dependent protein kinase (PKG) with KT5823. In reperfused hearts, stimulation of cGMP signalling led to decreased oedema development.. sGC/PKG activation during reperfusion reduces reperfusion-induced endothelial intercellular gap formation by attenuation of cytosolic calcium overload and reduction of contractile activation in endothelial cells. This mechanism protects the heart against reperfusion-induced oedema.

Topics: Animals; Calcium; Calcium-Binding Proteins; Carbazoles; Cell Hypoxia; Cells, Cultured; Coronary Vessels; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Cytosol; Edema, Cardiac; Endoplasmic Reticulum; Endothelial Cells; Enzyme Activators; Gap Junctions; Guanylate Cyclase; Homeostasis; Hydrazines; Male; Myocardial Reperfusion Injury; Myosin Light Chains; ortho-Aminobenzoates; Phosphorylation; Protein Kinase Inhibitors; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Second Messenger Systems; Soluble Guanylyl Cyclase; Sulfonamides; Time Factors