Regulatory Effects Of CCK-8 On Changes In Reactivity Of Aorta And Pulmonary Artery And Its Mechanisms During Endotoxic Shock

It has been well documented that cholecystokinin (CCK), a kind of brain-gut peptide, is involved in many physiological and pathophysiological processes. The actions of CCK are mainly mediated by two distinct receptors, referred to as CCK-A receptor (CCK-AR) and CCK-B receptor (CCK-BR). Sulfated cholecystokinin-octapeptide (CCK-8) is the minimum sequence for biological activity. The actions of CCK have been studied widely in nervous system, digestive system, and endocrine system in the past years. Effect of CCK-8 on reversing hemorrhagic shock in rats was reported by Riepl and Guarini respectively in the late of 1980s. In the early of 1990s, Holmgren reported that CCK-8 increased pulmonary blood flow. In 1996,it was found that CCK-8 had the effect of anti-endotoxic shock (ES) for the first time in our laboratory, CCK could protect cells function, attenuate the pathomorphological changes of main organs , decrease the mortality . During ES, the clearance rate of CCK-8 was decreased in lung and the CCK-8 content in blood was increased. The main action of CCK-8 was to improve the circulation state of ES, CCK-8 could partly reverse the fall of mean artery pressure (MAP) and the rise of pulmonary artery pressure (PAP), but the mechanism was not clear. Lipopolysaccharide (LPS), a main component of bacterial endotoxin, can induce ES. Intestinal bacterial endotoxemia occur frequently in the late stages of all kinds of shock. The purposes of the present study were to investigate the effects of CCK-8 on aortic hypo-reactivity and pulmonary arterial hyper-reactivity, and itsmechanisms in ES rabbits or LPS-treated aortic smooth muscle cell (ASMC) and pulmonary artery smooth muscle cell (PASMC) of rats. Our studies were as following: (1) Regulatory effects of CCK-8 on changes in MAP and PAP in ES rabbits; (2) Effects of CCK-8 on changes in vascular (thoracic aorta, pulmonary artery) reactivity; (3) LPS-induced expression of CCK-R mRNA in vascular tissues, ASMC and PASMC; (4) CCK-8 inhibiting the expression of iNOS mRNA and HO-1 mRNA in ASMC induced by LPS.1 Regulatory effects of CCK-8 on changes in MAP and PAP in ES rabbitsThe aim of this study was to simultaneously observe the effects of CCK-8 on changes in MAP, PAP in ES rabbits. Forty male rabbits were divided into five groups randomly (n=8 in each group):⑴ Control group, saline(0.8ml/kg, iv) was injected ⑵ LPS group, LPS (8mg·0.8ml-1·㎏-1, iv) was injected slowly within 10 min. ⑶ CCK-8+LPS group, CCK-8 (15μg·0.8ml-1·㎏-1, iv) was injected 30 min before LPS administration.⑷ Proglumide (Pro) +LPS group, Pro (an antagonist for CCK recptor, 1mg·0.8ml-1·㎏-1, iv) was injected 30 min before LPS administration.⑸CCK-8 group, CCK-8(15μg·0.8ml-1·㎏-1)was injected. The rabbits were anesthetized with 25% urethane(iv). The left common carotid artery was exposed, and a catheter was inserted and advanced into thoracic aorta. Another catheter was inserted into pulmonary artery through the right carotid vein. The changes in MAP and PAP were measured by physiological record instrument in these five groups for 5 hours. The contents of nitric oxide (NO) and malondialdehyde(MDA), the activity of nitric oxide synthase (NOS) and superoxide dismutase(SOD)in plasma were measured before drug delivery(0h) and 1h, 3h or 5h after drug delivery, respectively. The rabbits were killed after 5h.The thoracic aorta and pulmonary artery were excised. A part of arterial sample was fixed withparaformaldehyde and chopped into slices, then stained by HE. The pathomorphological changes were observed under light microscope. The other part of the sample was fixed with 2.5% or 4% glutaral to observe the cellular ultrastructure changes of vascular endothelium by electron microscope. The experimental results were as follows:①The MAP began to reduce at 0.5h after LPS injection, reached to the lowest point at 2h, and continued to 5h. The MAP significantly reduced, compared with control group (P<0.01) in the whole experimental course. Whereas the PAP increased significan...