Platelets and mediators in the carrageenin rat paw oedema

A number of similarities exist between several aspects of the imflammation process and the changes occurring in platelets during aggregation. This has initiated the search for a specific role of platelets in inflammation. The aim of our experiments was to investigate firstly whether during an acute inflammatory process platelets accumulate in the inflamed area and secondly whether the inflammation has an effect on the properties of the platelets. Rat platelets were labeled with 51Cr and injected into the tail vein of rats with a carrageenin-induced edema in one of the hind paws. The amount of radioactivity was measured in the inflamed paw and compared to the control one in the 24 hr following the injection. An accumulation of platelets was found at 3-4 hr after the injection of the carrageenin which disappeared later. Maximal swelling occurred after 5 hr. The aggregability of the platelets was determined at different times of the inflammatory process. After 2 hr, a decrease was observed which was higher after 4 and 6 hr. This effect might be due to the release of mediators during the inflammation.