The effect of atrial natriuretic peptide (ANP) on cytosolic free calcium ([Ca2+](i)) was studied in monolayers of cultured vascular smooth muscle (VSM) cells loaded with a fluorescent calcium indicator, fura-2. ANP (atriopeptin III, 10-8 M) decreased the resting level of [Ca2+](i) and sustained rises in [Ca2+](i) following peak levels induced by vasoconstrictive hormones (angiotensin II or vasopressin). ANP also decreased a rise in [Ca2+](i) induced by high potassium (high K+) depolarization. The initial rise in [Ca2+](i) induced by vasopressin was not inhibited by ANP. On the other hand, calcium antagonists (nicardipine or nifedipine) inhibited the high K+-induced rise in [Ca2+](i), whereas there was no effect on rises in [Ca2+](i) induced by vasopressin. These results suggest that calcium antagonists inhibit voltage-dependent calcium channels, while ANP can decrease [Ca2+](i) presumably through a stimulation of calcium-extrusion active transports in vascular smooth muscle cells.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine