Abstract
To investigate the pathogenesis of the onsets of atherosclerosis, myocardial infarction and cerebral thrombosis, we studied the effets of the extracts obtained from aortic tissues on platelet aggregation, as these onsets are closely related to arterial thrombosis, formation of which depends on platelet aggregability, arterial wall constituents and so on.
Seven human aortas were collected at autopsy within 5 hours after death. Samples were taken from intima and medial layers of uninvolved aortas, fibrous plaques and meidal layer beneath the plaques. They were shaken gently with 0.15M sodium chloride (1:5w/v), pH7.4, at 4°C for 24 hours and them centrifuged at 1.000G for 30 minutes. The residues were homogenized with 0.15M sodium chloride (1:5w/v), pH7.4, and then centrifuged at 1.000G for 30 minutes. The middle layers which were floated by centrifugation were used for the estimation of the effects of the extracts on platelet aggregation.
None of the extracts obtained by gentle shaking aggregated platelets. But platelet aggregations induced by ADP which was mixed with any kind of extracts prepared by gentle shaking were inhibited markedly compared to that of equimolar ADP. The aggregations by premixed epinephrine or norepinephrine with the extract prepared by gentle shaking were more accentuated than that of epinephrine or norepinephrine. Almost no effect on platelet aggregability was found by pre-mixed collagen with any kind of extracts by gentle shaking.
All of the extracts prepared by homogenization aggregated platelets. The extract-induced aggregation curves were similar to that of collagen. This fact may suggest that the extraced substance which aggregates platelets is arterial collagen.
From the results of this experiment, we can say that a condition which causes release of high amounts of catecholamines tends toward thrombus formation by platelet aggregation. Moreover, it may induce the onset of atherosclerosis, myocardial infarction and cerbral thrombosis.
