Summary
In a model using an isolated rabbit mesenteric preparation microvessels were transected
and the time until haemostatic plugs formed was registered. Perfusion of platelet
rich plasma gave no haemostasis whereas whole blood did. Addition of chlorpromazine
or adenosine to the whole blood significantly prolonged the time for haemostasis,
and addition of ADP to the platelet rich plasma significantly shortened it. It is
concluded that red cells are necessary for a normal haemostasis in this model, probably
by a combination of a haemodynamic and ADP releasing effect.
The fundamental role of platelets in haemostatic plug formation is unquestionable
but there are still problems concerning the stimulus for this process to start. Three
platelet aggregating substances have been discussed – thrombin, adenosine diphosphate
(ADP) and collagen. Evidence speaking in favour of thrombin is, however, very minimal,
and the discussion has to be focused on collagen and ADP. In an in vitro system using
polyethylene tubings we have shown that "haemostasis" can be obtained without the
presence of collagen but against these results can be argued that it is only another
in vitro test for platelet aggregation (1).
To be able to induce haemostasis in this model, however, the presence of red blood
cells is necessary. To further study this problem we have developed a model where
haemostatic plug formation can be studied in the isolated rabbit mesentery and we
have briefly reported on this (2).
Thus, it is possible to perfuse the vessels with whole blood as well as with platelet
rich plasma (PRP) and different pharmacological agents of importance.
Key words
Platelet plug - Rabbit
