An electron microscope study of arteriolar branching sites in the normal gastric submucosa of rats and in experimental gastric ulcer.

To observe the branching site of the rat gastric submucosal arteriole toward the mucosal capillary network, we used vascular corrosion casting, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), under various conditions, including the normal state, water immersion restraint stress for 24 h, ethanol-induced ulcer and administration of low and high doses of noradrenaline. In normal rats, the branching site of the submucosal arteriole toward the mucosa was slightly narrowed, as seen in the cast observations. The SEM and TEM observations revealed that this narrowing was due to the presence of the so-called "intra-arterial cushion". In the restraint stress rats, this narrowing was increased. TEM and direct SEM observation of the intraarterial cushion showed much the same findings. In the noradrenaline administered rats, similar changes were observed but not so in the rats with an ethanol-induced ulcer. Arterio-venous-anastomoses (AVA) were not observed in the submucosa, under any of the conditions used. We suggest that the submucosal intra-arterial cushions occurring at the branching sites of the submucosal arterioles may play an important role in regulating blood flow to the gastric mucosa.