Arterial bleeding time in mesentery

Male Sprague-Dawley rats weighing 180-240 g receive the test compound or the vehicle (controls) by oral, intraperitoneal or intravenous administration. After the end of the absorption time (i.p. 30 min, p.o. 60 min, i.v. variable), the animals are anesthetized by intraperitoneal injection of 60 mg/kg pentobarbital sodium. Rats are placed on an electrically warmed table at 37 °C. 

The abdomen is opened by a mid-line incision and the mesentery is lifted to display the mesenteric arteries. The mesentery is draped over a plastic plate and superfused continuously with Tyrode s solution maintained at 37 °C. Bleeding times are determined with small mesenteric arteries (125-250 fim external diameter) at the junction of mesentery with intestines. 

Adipose tissue surrounding the vessels is carefully cut with a surgical blade. 

Arteries are punctured with a hypodermic needle (25 gauge 16 x 5/10 mm). The bleeding time of the mesenteric blood vessels is observed through a microscope at a magnification of 40 x. The time in seconds is determined from the puncturing until the bleeding is arrested by a hemostatic plug. 

Mean values of bleeding times (s) are determined for each dosage group (4-6 animals, 4-6 punctures each) and compared to the controls. 

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