Abstract
A simple technique has been developed for resolving cellular
45Ca efflux from intestinal smooth muscle into two exponential components. Strips of taenia coli from guinea pig are labeled with
45Ca for three hours and then washed in an ice-cold, oxygenated medium containing 5 mM CaEGTA and 1.5 mM excess Ca
2+ for 40 minutes in order to remove extracellularly bound label. Tissues subsequently placed in a control physiological solution at 37°C exhibit an efflux profile of
45Ca which can be resolved into two exponential components. The apparent magnitudes and rate constants of these components are sensitive to ionic alterations of the medium and to biochemical manipulation of the Ca
2+ compartmentalization within the cells.
