Gastric mucosal exposure to histamine in rats is followed by absorption of histamine but not mucosal hyperemia.

BACKGROUND/AIMS: Superficial mucosal damage is associated with mucosal hyperemia and release of histamine into venous blood and gastric lumen. This study was designed to examine if histamine administrated directly to gastric mucosa becomes absorbed and transported away with blood, and if so whether it is capable of increasing gastric mucosal blood flow.

METHODOLOGY

Superficial mucosal injury was induced by exposing chambered rat stomachs to 2 M NaCl for 10 min, and 45 min later 4.5 x 10(-2) or 4.5 x 10(-3) M histamine was instilled into the chamber. Mucosal blood flow was determined by radioactive microspheres and continuously by Laser Doppler flowmetry.

RESULTS

Histamine concentration in arterial blood was markedly increased 15 min after administration of histamine. The mucosal blood flow did not increase after application of histamine. Significant increase in heart rate and fall in arterial blood pressure were observed. Similar results were obtained after application of histamine to normal mucosa.

CONCLUSIONS

Histamine applied to injured or normal gastric mucosa of rats becomes transported via capillaries and venules to the systemic circulation, but does not reach terminal arterioles in quantities large enough to cause vasodilatation.