Organization of Ca2+ stores in vascular smooth muscle: functional implications.

Much evidence suggests that caffeine/ryanodine (Caf/Ry)-releasable and inositol-1,4,5-trisphosphate (InsP3)-releasable Ca2+ stores in the sarcoplasmic reticulum (SR) of smooth muscles are at least partially distinct. We directly visualized SR stores in primary-cultured rat mesenteric artery myocytes with high-resolution digital imaging and the low-affinity Ca2, indicator, Furaptra (Kd = 75.6 microM).