Endoglin regulates nitric oxide‐dependent vasodilatation

Endoglin is a membrane glycoprotein that plays an important role in cardiovascular development and angiogenesis. We examined the role of endoglin in the control of vascular tone by measuring nitric oxide (NO)‐dependent vasodilation in haploinsufficient mice ( Eng +/− ) and their Eng +/+ littermates. The vasodilatory effect of acetylcholine, bradykinin, and sodium nitroprusside was assessed in anesthetized mice; in isolated, perfused hindlimbs; and in aortic rings. The substantial hypotensive and vasodilatory response induced by acetylcholine and bradykinin in Eng +/+ was markedly reduced in Eng +/− mice. Both kinds of animals had similar responses to sodium nitroprusside, suggesting that the deficient vasodilatory effect is not due to a NO response impairment. Urinary and plasma concentrations of nitrites, a NO metabolite, were lower in Eng +/− than in Eng +/+ mice. The levels of endothelial nitric oxide synthase (eNOS) in kidneys and femoral arteries were about half in Eng +/− than in Eng +/+ mice and were also reduced in primary cultures of aortic endothelial cells from Eng +/− compared with those from Eng +/+ mice. Furthermore, overexpression or suppression of endoglin in cultured cells induced a marked increase or decrease in the protein levels of eNOS, respectively. Thus, our results in vivo and in vitro demonstrate a relationship between endoglin and NO‐dependent vasodilation mediated by the regulation of eNOS expression.