Evagination of vascular smooth muscle cells during the early stages ofCrotalaria pulmonary hypertension

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Abstract
Adult female Wistar albino rats (15) were fed a diet containing powdered C. spectabilis seeds for periods up to 5 wk. EM studies were carried out on the lungs of these animals and of 3 control rats. Both groups of animals showed protuberances of smooth muscle cells. In the control rats such protuberances were small and filled out spaces created by undulation of the internal elastic lamina produced by collapse of the vessel. These protuberances could be prevented by fixing the lung in distension. Evaginations of smooth muscle cells in the test rats were larger, devoid of myofilaments and organelles and arose from the parent cell between dense attachment points on the sarcolemma. Frequently they arose through a narrow cytoplasmic isthmus and had such electron-lucent contents as to resemble a cyst within the endothelium. They pressed onto the undersurface of endothelial cells which fitted over them like a cap. Such evaginations may arise as a result of sustained vasoconstriction.