AIMTo investigate the effects of atrial natriuretic peptide(ANP) on constriction and relaxation of pulmonary artery and aorta in endotoxemia rat in vitro.

METHODS24 male SD rats were randomly divided into 3 groups, control group, LPS group, ANP therapy group. These groups were injected physiologic salt water, lipopolysaccharide (LPS 2 mg/kg) and LPS + ANP(LPS 2 mg/kg, ANP 2 microg/kg) into vein respectively. After 4 hours, rats were exsanguinated to kill and aorta and pulmonary artery were separated from heart-lung for experiment of blood vessel rings. Constriction effects of aorta and pulmonary artery by norepinephrine (NE), relaxation of aorta and pulmonary artery by acetylcholine (ACh) and sodium nitroprusside SNP) observed by perfusion system in vitro.

RESULTSSensitiveness of NE-induced (10(-9)-10(-7) mol/L) constriction of aorta in LPS group was attenuated and EC50 was increased, but its strength (3 x 10(-7)-10(-6) mol/L) was greater comparing with control group (P < 0.01). In ANP group, the NE-induced contractility of aorta was similar to LPS group (P > 0.05). Comparing with control group, NE-induced constriction of pulmonary artery exposure to LPS was reinforced especially in 3 x 10(-7)-10(-6) mol/L of NE (P < 0.01), but its EC50 was obviously higher (P <0.05). There was no significant difference between ANP group and control group in constriction of pulmonary artery (P > 0.05). Relaxation and sensitiveness of aorta and pulmonary artery exposure to LPS were evidently improved in ANP therapy group induced by ACh and SNP respectively (P < 0.01, P < 0.05) and their EC50 markedly decreased comparing with LPS group (P < 0.01, P < 0.05) respectively.

CONCLUSIONANP can suppress the reinforcing of NE-induced constriction of pulmonary artery exposure to LPS and partly or entirely reverse the attenuated relaxation of pulmonary artery and aorta induced by ACh and SNP in endotoxemia rats.