Assessment of hemodynamic changes in rat stomachs by laser Doppler velocimetry and reflectance spectrophotometry: Effects of ethanol and prostaglandin E2 under ischemic and congestive conditions

One of the ulcerogenic mechanisms by which ethanol induces mucosal lesions in the stomach is the depression of gastric mucosal blood flow (GMBF). The goal of this study was to determine whether lesion formation is the result of vascular ischemia alone or ischemia combined with congestion. The aims of this study were to answer this question by evaluating the relationship between GMBF, oxygen saturation (IS0₂) and hemoglobin volume (IHb) in the gastric mucosa under the influences of ethanol and prostaglandin E₂ (PGE₂) in the ischemic and congestive states, using a laser Doppler flowmeter and tissue spectrum analyzer. Ligation of the gastric celiac artery or vein markedly decreased the GMBF and the IS0₂ level. The former procedure also reduced but the latter increased the IHb level. Ethanol administration produced effects similar to venous ligation, i.e. vascular stasis with ischemia. There was a negative correlation between GMBF and severity oflesion formation after ethanol administration. However, at the lesion site all the hemodynamic parameters were significantly reduced, indicating that a necrotic condition had occurred. PGE₂ preincubation (25 pg) elevated GMBF, IS0₂ and IHb levels. It also alleviated the reduction of blood flow induced by ethanol and increased the recovery rate of GMBF and IS0₂ after the release of arterial or venous ligation. It is concluded that the decrease in blood flow due to ethanol is probably caused by constriction of venules rather than arterioles inside the mucosa, and this effect could lead to vascular congestion. PGE₂ probably dilates both arterioles and venules in the gastric mucosa and thereby increases the blood flow in the gastric mucosa. The concurrent use of a laser Doppler flowmeter and the tissue spectrum analyzer is a useful experimental tool to define the hemodynamic changes under different experimental conditions, especially in the clarification of ulcerogenic mechanisms in the stomach.