[An experimental study of chemical embolization using conjugated estrogen--ultrastructural observations on rat...

We previously reported a new embolization method using conjugated estrogen and also a basic study which demonstrated that conjugated estrogen produced microcirculatory disturbance. To clarify the mechanism of this microcirculatory disturbance following the administration of conjugated estrogen, the changes of vascular endothelial cells and red blood cells were studied. After intra-arterial infusion of conjugated estrogen into rat mesenteric arteries, microcirculatory changes were observed with a biomicroscope, and also ultrastructural changes of vascular endothelial cells and red blood cells were examined. As a result, biomicroscopically, mesenteric microcirculatory disturbance in proportion to the doses of conjugated estrogens was seen and stasis of the microcirculation was finally observed in all rats. Ultrastructural observations revealed an appearance of spherocytes soon after the infusion and injury of vascular endothelial cells perfused with conjugated estrogen. Vascular endothelial cells were injured remarkably, including their plasma membrane, cytoplasm, and nuclei when mesenteric microcirculation showed sludging under the biomicroscope. At the stage of stasis, endothelial cells were severely injured and most of the vessels were filled with spherocytes. From these results, it was presumed that vascular endothelial injury and alterations of red blood cells into spherocytes induced by conjugated estrogen were the major factors of embolization effect of the conjugated estrogen. Furthermore, conjugated estrogen was considered as an effective embolic material because not only main arteries but microcirculations could be occluded by its intraarterial infusion.