EFFECT OF CAPTOPRIL ON VASOCONSTRICTION AND CA2-MUSCLE( FLUXES IN AORTIC SMOOTH)

The effects of captopril on the response of cytosolic free Ca2+ concen tration in cultured vascular smooth muscle cells of aortas from Wistar -Kyoto and spontaneously hypertensive rats to angiotensin II (Ang II) and bradykinin were studied using fura 2. Incubation with captopril fo r longer than 10 minutes caused a decreased response of cytosolic free Ca2+ to Ang II and bradykinin. Maximal effects of captopril were obse rved after a 40-minute incubation. The inhibitory effect of captopril was abolished in Ca2+-free medium, suggesting that captopril acts by b locking Ca2+ influx. Similar effects were observed with enalaprilat. I sometric contraction of aortic strips induced by Ang II in normotensiv e rats was reduced from 6.5+/-2.5 to 1.8+/-0.6 mN by a 40-minute incub ation with 1 mu mol/L captopril (P=.016). Enalaprilat similarly decrea sed the Ang II-induced contraction. Besides the inhibition of the angi otensin converting enzyme, direct effects of Ang II converting enzyme inhibitors on vascular contraction and Ca2+ influx in vascular smooth muscle cells may be of therapeutic relevance.