Since endothelial damage is a trigger for the progression of atherosclerosis, we evaluated the clinical utility of prostaglandin E1 (PGE1) in relation to peripheral blood flow and regulation of hepatocyte growth factor (HGF), an angiogenic growth factor, in patients with peripheral arterial disease (PAD). Fourteen male patients with PAD who showed the characteristic symptoms of arteriosclerosis obliterans (Fontaine I: n=2; Fontaine II: n=4; Fontaine III: n=2; Fontaine IV: n=6), confirmed by angiography, were enrolled in this study. Patients were administrated synthetic PGE1 at a dose of 120 microg per day for 14 consecutive days. Measurement of peripheral blood flow and serum HGF concentration was performed before PGE1 treatment and after 14 days of administration. Interestingly, intravenous administration of PGE1 for 2 weeks significantly increased the blood flow as assessed by a laser Doppler imager (p<0.01). In patients with Fontaine III and IV, serum HGF concentration was significantly higher than that in patients with Fontaine I or II and normal subjects. Of importance, administration of PGE1 further increased serum HGF concentration as compared to that before treatment (p<0.01). The increase in circulating HGF might work as a compensatory mechanism to decrease local HGF expression in patients with PAD, since HGF acts as an angiogenic growth factor with anti-apoptotic actions on endothelial cells. Moreover, to confirm the stimulatory effect of PGE1 on HGF in vessels, we employed an in vitro culture system. PGE1 increased HGF production and the growth of human cultured vascular endothelial cells. The stimulatory effect of PGE1 on HGF production might be due to an increase in cAMP, since forskolin and 8-bromo-cAMP induced HGF production. In conclusion, we demonstrated that administration of PGE1 stimulated peripheral blood flow, accompanied by an increase in systemic HGF concentration. Also, our in vitro data suggested that PGE1 augmented not only the systemic HGF level, but also local HGF production, probably through cAMP accumulation, resulting in improvement of endothelial function and blood flow.