Angiotensin-(1-9),the product of angiotensin I conversion in platelets,enhances arterial thrombosis in rats

Angiotensin (ang) (1-9) is the renin-angiotensin-system peptide found in the plasma of healthy volunteers and after angiotensin-converting-enzyme inhibitors therapy. in vitro experiments proved that ang-(1-9) may be produced from ang i. in our study,we tried to expand the poor data about the in vivo properties of ang-(1-9). we revealed that ang-(1-9) enhanced electrically stimulated arterial thrombosis in the carotid artery of wistar rats. losartan,a selective blocker of at1 receptor for ang ii,abolished the prothrombotic activity of ang-(1-9). this peptide increased plasma level of fibrinogen,augments fibrin generation,and similarly to ang ii,potentiated collagen induced platelet aggregation. using hplc,we found that after incubation of ang-(1-9) with platelet homogenates or after intravenous administration this peptide is converted to ang ii. we concluded that ang-(1-9) exerts an ang ii-like prothrombotic effect due to the conversion to ang ii in the circulatory system of rats and that platelets are involved in this process.