The effect of unfractionated and low-molecular-weight heparin on the release of prostacyclin from the arterial wall.

Heparin is widely used as an antithrombotic agent, but one reported complication is thrombocytopenia associated with platelet aggregation. The mechanism is not fully clear but heparin interference in the prostaglandin production has been proposed. To investigate if heparin interacts with the production of prostacyclin from the vessel wall, and if low-molecular-weight heparin differs from unfractionated heparin in this respect, excised rabbit aortas were studied in a perfusion model. The vessels were perfused ex vivo for 5 x 15 min and in the last period arachidonic acid was added. Unfragmented heparin (500 IU/kg body weight) or low-molecular-weight heparin (LMWH) (500 antifactor Xa units/kg body weight) were given either 15 min before harvesting the vessels or added directly to the perfusate. The stable degradation product for prostacyclin, 6-keto-PGF1 alpha was not altered by addition of these agents. It is concluded that heparin and LMWH per se do not interact with the prostacyclin system in normal rabbit aortas in the doses studied.