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 endothelia l cells (PBCEC) respond to bradykinin with an enhanced intracellular c ytosolic calcium concentration [Ca2+](i) with subsequent formation of nitric oxide (NO) and prostacyclin (PGI(2)). In addition we examined w hether these cells synthetize and release kinins that may accumulate d uring angiotensin-converting enzyme (ACE) inhibition. [Ca2+](i) was as sessed by,the fluorescent dye Fura-2, NO formation by determination of intracellular cyclic GMP and PGI(2) by a specific radioimmunoassay fo r 6-ketoprostaglandin F1(alpha). Bradykinin and the ACE inhibitor rami prilat concentration-dependently increased the formation of cyclic GMP which was completely prevented by the stereospecific inhibitor of NO synthase, N-G-nitro-L-arginine. Also the specific B-2-kinin receptor a ntagonist icatibant (Hoe 140) abolished the increase in cyclic GMP as well as the ramiprilat-induced increase in PGI, formation. The data de monstrate the existence of B-2-kinin receptors and ACE activity in PBC EC. Moreover PBCEC are capable of producing and releasing kinins in am ounts that lead via stimulation of B-2-kinin receptors to an enhanced [Ca2+]i as well as NO and PGI(2) synthesis and release, provided that degradation of kinins is prevented by inhibition of endothelial ACE ac tivity.