Contractile responses of isolated frog aortic strips to angiotensin II (A II) were not affected by concentration of verapamil that inhibited responses to potassium chloride. Inhibition of responses to both agonists was observed in the presence of manganese chloride. Preparations fully contracted with potassium chloride responded to A II to the same extent as control. A II responses persisted (though significantly reduced) even after 2 hr perfusion in calcium free solution. The results indicate mobilization of both cellular and extracellular calcium pools in A II induced contractions. Receptor operated channels (ROC) appear to be mediating transmembrane influx of Ca2+ during contractile process.
Activator calcium, angiotensin II, calcium free ringer, EDTA, frog aorta, manganese chloride, potassium depolarization, receptor operated channels, verapamil