Thromboembolic Reaction Following Wall Puncture in Arterioles and Venules of the Rabbit Mesentery

Abstract

SummaryThe walls of rabbit mesenteric arterioles and venules (diameter 20 to 40 pm) were punctured with glass micropipets (tip diameter 6 to 8 pm). Thromboembolic reactions resulting from this standardized, small mechanical vessel wall injury could be quantified in vivo with the use of intravital video-microscopy. Following induction of the injury thrombus growth started immediately (<0.1 s). Bleeding times were short, on the average less than 2 s, and did not differ between arterioles and venules. The duration of the embolization process was significantly longer in arterioles than in venules (median 101 and 17 s, respectively), and more emboli were produced in arterioles than in venules (median 6 and 1, respectively). Arteriolar thrombi were more effective in plugging the punctured holes than venular thrombi. The differences in thromboembolic reaction between arterioles and venules, as found in the present study, can probably not be explained by fluid dynamic factors.

Endogenous Nitric Oxide Protects Against Thromboembolism in Venules But Not in Arterioles

“…All values are within the ranges normally found in anesthetized rabbits. 19,26,30 No significant difference in weight, hemoglobin, hematocrit, platelets, or heart rate was found between rabbits of the different groups. In the course of the experiment, the combination of SNP with L-NA, however, reduced mean arterial blood pressure, resulting in a significantly lower blood pressure in this group than in the other groups (PϽ.001).…”

“…These values are within the normal ranges for rabbits. 19,26 No statistical differences existed between the experimental groups (see "Results").…”

“…Vessel wall injury was induced mechanically by puncture with a glass micropipet (tip diameter Ϸ6 m), as previously described. 19 To be certain that all layers of the wall were damaged, puncture was considered to be successful only if red blood cells could be seen leaving the vessel.…”

“…Most of the studies performed have focused on the antithrombogenic properties of NO in arterioles [11][12][13] or arteries, 14 -18 but not in venules. Since in vivo the thromboembolic reaction to vessel wall injury differs between arterioles and venules of the same tissue, 19,20 it might be hypothesized that NO is differently involved in this process in these microvessels.…”

“…19 In the mesentery of anesthetized rabbits, the wall of arterioles and venules was punctured with a micropipet, and the ensuing thromboembolic reaction was studied with the use of intravital videomicroscopy. In the first series of experiments, the mesentery of one group of rabbits was locally superfused with L-NA or its vehicle; L-NA is an irreversible inhibitor of NOS 5 in the wall of rabbit blood vessels [21][22][23] and in rabbit platelets.…”