Enhancement of cytosolic calcium, prostacyclin and nitric oxide by bradykinin and the ACE inhibitor ramiprilat in porcine brain capillary endothelial cells

We studied whether primary cultured porcine brain capillary endothelial cells (PBCEC) respond to bradykinin with an enhanced intracellular cytosolic calcium concentration [Ca2+]i with subsequent formation of nitric oxide (NO) and prostacyclin (PGI2). In addition we examined whether these cells synthetize and release kinins that may accumulate during angiotensin-converting enzyme (ACE) inhibition. [Ca2+]i was assessed by the fluorescent dye Fura-2, NO formation by determination of intracellular cyclic GMP and PGI2 by a specific radioimmunoassay for 6-ketoprostaglandin F1 alpha. Bradykinin and the ACE inhibitor ramiprilat concentration-dependently increased the formation of cyclic GMP which was completely prevented by the stereospecific inhibitor of NO synthase, NG-nitro-L-arginine. Also the specific B2-kinin receptor antagonist icatibant (Hoe 140) abolished the increase in cyclic GMP as well as the ramiprilat-induced increase in PGI2 formation. The data demonstrate the existence of B2-kinin receptors and ACE activity in PBCEC. Moreover PBCEC are capable of producing and releasing kinins in amounts that lead via stimulation of B2-kinin receptors to an enhanced [Ca2+]i as well as NO and PGI2 synthesis and release, provided that degradation of kinins is prevented by inhibition of endothelial ACE activity.