[An ultrastructural study of capillary endothelial cells in toxemic placental villi using a quick quenching method].

The pathophysiological phenomena of placental microcirculation in cases of toxemia of pregnancy were studied. Fetal capillary endothelial cells, which were constituents of placental barrier, in chorionic villi from 5 normal and 10 toxemic pregnancies were ultrastructurally observed. The small pieces of tissue were prepared by a quick quenching & freeze substitution method, immediately after removal or after incubation in catecholamine solution. 1) In normal placentae, the thickness of the endothelial cells was uniform, and so was the distribution of cytoplasmic organelles. After incubation in catecholamine solution, endothelial cytoplasm partly protruded towards the capillary lumen, forming humps, which contained plenty of 6 nm diameter filaments which were thought to be actin filaments. 2) In toxemic placentae, 10nm diameter filaments increase to form bundles in endothelial cytoplasm. No cytoplasmic organelles were found here. Especially in placentae from severe toxemic pregnancies with IUGR, the augmentation of these filaments was so pronounced that the capillaries seemed as if they were solid molds, and it is possible that the blood flow is disturbed in these capillaries. 3) The endothelial cells occupied by bundles of filaments contained almost no organelles or pinocytotic vesicles. This fact suggests that the quantity of filaments affects the ability to actively transport the substances of mother and fetus.