Ultrastructural alterations of the coronary atrety induced by arterial spasm.

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Remarkable spasms of in-vitro swine coronary arteries immersed in Kreds Ringer were induced by application 3f histamine(10^<-3>M) and acetylcholine (10^<-3>M) but not by ergonovine,prostablandine _<2<alpha>>serotonin,and noradrenaline. In crder to observe the morphological changes of the arterial wall especially of the tunica intima during spasmic phases induced by histamine,the Ringer solution was promptly replaced by Karnovskey's fixatives.Intercellular clefts of the endothelia are extensively dilated such an extent that the intercellular vacuoles exist between the endothelial cells.Exfoliation of the endothelial cells from the tunica intima occurs in the limited regions.Some endothelial cells possess large intracellular vacuoles including various cell debrises.Furthermore,increase in the endothelial permeability is evident from marker experiments using HRP.The present observation indicates significant morphological damages occur in the tunica intima especially in the endothelia during the histamine-mediated coronary spasm.Such damages may increase in turn the endothelial permeability,and such sequences may multiply the coronary spasm.Slight spasms of the swine coronary artery were also induced by application of compound 48/80 (1mg/ml Ringer), a histamine liberator.Electron microscopy reveals a marked degranulation of endothelial specific granules (Weibel-Palade bodies) by this drug as in the case of the other vessels. Since these granules have been considered to be histamine reservoir sites,it is reasonable to consider that the arterial spasms by compound 48/80 are due to histamine mediated contraction of the tunica media.