Calcium gradients in single smooth muscle cells revealed by the digital imaging microscope using Fura-2

Abstract

Calcium is believed to control a variety of cellular processes, often with a high degree of spatial and temporal precision. For a cell to use Ca 2+ in this manner, mechanisms must exist for controlling the ion in a localized fashion. We have now gained insight into such mechanisms from studies which measured Ca2+ in single living cells with high resolution using a digital imaging microscope and the highly fluorescent Ca 2+-sensitive dye, Fura-2. Levels of Ca2+ in the cytoplasm, nucleus and sarcoplasmic reticulum (SR) are clearly different. Free [Ca 2+] in the nucleus and SR was greater than in the cytoplasm and these gradients were abolished by Ca2+ ionophores. When external Ca 2+ was raised..