Cyclical coronary flow reductions in conscious dogs equipped with ameroid constrictors to produce severe coronary narrowing

In conscious dogs equipped with ameroid constrictors to produce gradual coronary occlusion, coronary flow velocity was monitored prior to complete occlusion when coronary constriction was severe (resting flow velocity reduced by 10–50% from control recordings made 7–10 days after ameroid implantation). In six of the ten dogs, we observed spontaneous cyclical variations in coronary flow velocity, characterized by gradual reduction in flow followed by very abrupt restoration of flow. The cyclic coronary flow reductions were observed between 20 and 31 days after ameroid implantation. These changes in flow bear striking similarity to those observed by previous investigators using anesthetized, open-chest canine preparations, in which the role of platelets was clearly demonstrated. Consequently, we hypothesize that spontaneous platelet aggregation and de-aggregation within the severely narrowed coronary lumen (enclosed by the ameroid constrictors) could account for our observations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41746/1/395_2005_Article_BF01906748.pd

Platelet Function in Acute Experimental Pancreatitis

Acute pancreatitis (AP) is characterized by disturbances of pancreatic microcirculation. It remains unclear whether platelets contribute to these perfusion disturbances. The aim of our study was to investigate platelet activation and function in experimental AP. Acute pancreatitis was induced in rats: (1) control (n = 18; Ringer’s solution), (2) mild AP (n = 18; cerulein), and (3) severe AP (n = 18; glycodeoxycholic acid (GDOC) + cerulein). After 12 h, intravital microscopy was performed. Rhodamine-stained platelets were used to investigate velocity and endothelial adhesion in capillaries and venules. In addition, erythrocyte velocity and leukocyte adhesion were evaluated. Serum amylase, thromboxane A2, and histology were evaluated after 24 h in additional animals of each group. Results showed that 24 h after cerulein application, histology exhibited a mild AP, whereas GDOC induced severe necrotizing AP. Intravital microscopy showed significantly more platelet–endothelium interaction, reduced erythrocyte velocity, and increased leukocyte adherence in animals with AP compared to control animals. Thromboxane levels were significantly elevated in all AP animals and correlated with the extent of platelet activation and severity of AP. In conclusion, platelet activation plays an important role in acute, especially necrotizing, pancreatitis. Mainly temporary platelet–endothelium interaction is observed during mild AP, whereas severe AP is characterized by firm adhesion with consecutive coagulatory activation and perfusion failure