A study on the in vivo production of thrombosis in rat mesenteric arterioles and action of prostaglandin (PG) I2 on the thrombosis.

We have investigated reproducible and quantitative thrombus formation in rat mesenteric arterioles using electrical stimulation under an inverted microscope. In vivo thrombi were formed in arterioles of 30-40 micrometers diameter by electrical stimulation using a tungsten electrode with a tip of 5 micrometers diameter. A "threshold" response was defined as one in which platelets adhered to the injured site of vascular wall and formed a white body which flowed away intermittently. The thrombus formations were classified into three stages: stage I, thrombi covering up less than 20% of the vessel lumen; stage II, when 20% to 40% of the lumen was covered; or state III, when more than 40% was covered. This preparation was demonstrated to be valuable for testing the potency of anti-thrombotic drugs if we performed the experiment within 2 hr after removing the mesentery from the peritoneal cavity which exposed it to air. PGl2, t a dose of 0.5 micrograms/100 g intravenously administered, inhibited the growth of the thrombus at stage II and III. PGE1, PGD2 and PGE2 had no effect at the same dose on these stages. The threshold response was significantly suppressed by both PGI2 and PGE1 at doses of 5 micrograms/100 g.