Plasma 5-hydroxytryptamine And Histamine Levels In Acute Experimental Pulmonary Thromboembolism.

Objective:This study used a model of pulmonary thromboembolism(PTE) in guinea pigs induced by external jugular vein injection of autologous blood clots, to study the changes of the concentrations in 5-hydroxytryptamine and histamine in plasma.Methods:(1) The induction of animal model and the sampling of blood and tissue: Thirty guinea pigs were divided into experimental group (n=26,PTE group) and control group (n=4,sham group); the PTE group was divided into 6 subgroups : 1d group(n=6), 3d,5d,7d,14d,21d(each group n=4). Blood clots were made with blood taken from guinea pigs in PTE group---drawn vein blood(0.5ml) and poured into a sterile glass plate. After coagulation, the clot was cut into small particles(2×2×2mm). PTE animal model was induced by external jugular vein injection of 8 pieces of clot particles. The model was designed such that sham guinea pigs were exposed to same surgical stressors as the PTE ones but without mechanical pulmonary occlusion. Seven guinea pigs of the 1d group at the 0.25h,0.5h,1h,1.5h,2h and 24h (hour) after operation and the carotid artery was cannulated after anesthetization for arterial blood sampling to isolate plasma. The other groups respectively at 3std,5std ,7std, 14std, 21std. The guinea pigs were sacrificed by bloodletting after injecting heparin 2ml(25u/ml). The two lungs were harvested and fixed in 10% formalin solution until embedded in paraffin.(2) The detection of plasma 5-hydroxytryptamine and Histamine: The levels of plasma 5-hydroxytryptamine and Histamine were detected with Enzyme-linked immunoadsordent assay (ELISA) method.(3) The ordinary pathological examination of section of paraffin embedded tissue: Haematoxyllin-eosin (HE) staining was used to observe the form and the site of embolus in the pulmonary artery.Results:(1) The pathological results: In the 1std and 2std groups, there were secondary thrombosis in the pulmonary arteries(above section).The embolized areas present as pulmonary atelectasis with a great deal of red cells permeate into pulmonary alveolus, and without damaging of lung tissue. After 7d there was no secondary thrombosis in pulmonary arteries.(2) The detecting results of plasma vasoactive factors: Plasma 5-HT concentrations rose 30 min after embolization. Artery plasma levels of 5-HT increased from 51±37ng/ml to 152±41.8ng/ml(p<0.01),then decreased gradually to base line after 24 hour. However venous plasma 5-HT levels were not significantly altered after embolization. Both artery and venous plasma levels of histamine rose to the peak after 15min of embolization(p<0.01).slightly higher during 3-5d, and then decreased to the base line.Conclusion:(1) A model of PTE in guinea pigs can be induced by jugular vein injection of autologous blood clots.(2) Healthy animals, single time pulmonary thromboembolism, there were often pulmonary infarction incompletely, after 5-7 days it can be absorbed absolutely. Because lung has several blood supply, pulmonary infarction happened seldom.(3) Artery plasma 5-HT concentrations rose significantly during 1 hour after embolization. However venous plasma 5-HT levels were not significantly altered. Both artery and venous plasma levels of histamine rose to the peak after 15min of embolization, after 5d it decreased to the base line.