Study of "prostacyclin-like" activity in the rat blood vessel: changes in prostacyclin production related to body weight.

The prostacyclin-producing capacity of various blood vessels was studied using platelet aggregation bioassay in rats of different ages. Results showed that --the PGI2 producing capacity of arteries was five to tenfold of the respective veins; --in the arteries the PGI2 production calculated for unit vascular mass declined from the centre to the periphery, despite the relative increase of endothelial surface area. This points to the importance of other vascular elements in the control of PGI2 production; --the PGI2 forming activity of some blood vessels increased with the age up to a limit (300-400 g body weight), decreasing thereafter. Based on these results we conclude that major part of PGI2 in systemic blood originates from the large arteries, whereas the low PGI2 production of the veins might play a role, among others, in the more frequent occurrence of venous thrombosis.