[Hemodynamic effects on embryonic endocardial morphology].

The modifications of endocardial cells on bulbar cushions of the chick embryonic heart have been studied using the SEM following an experimental stenosis of the pulmonary artery. This stenosis was produced by the occlusion of both 6th aortic arches on the 4th day of incubation by silver microclips. The formation of small craterlike defects was observed on the distal ventral and proximal left bulbar cushions. Giant intercellular openings appeared on the top of the proximal left bulbar cushion indicating some acceleration of the blood flow in this region. Phagocytes traversing the endocardium have been seen more frequently than in controls. It seems that the endocardium is relatively resistant to the described hemodynamic changes. These changes modify the passage of phagocytes into the blood stream as well as cell movements and exocytosis.