Simultaneous registration of contraction and cytosolic calcium ([Ca2+](i))of smooth muscle strips using front-surface fluorimetry

Using front-surface fluorimetry with fura-2-loaded smooth muscle strips, si multaneous registration of the cytosolic calcium concentration ([Ca2+](i)) changes and tension development was done under the action of 40 mM KCl and the myotropic peptide 10(-6) M angiotensin II. The strips were mounted vert ically, connected to a force transducer that keeps a basal isometric tensio n of 0.5 g, and maintained in a bathing solution oxygenated at 37 degrees C . The fiber-optic platform FluoroMax-2 accessory 1950F was used to do the r emote sensing for the samples. Light from the excitation spectrometer (Fluo roMax-2), alternating between 340 and 380 nm, was focused onto the fiber-op tic bundle and directed to the smooth muscle strip. The fluorescence (505 n m) was collected and redirected to the emission port of the fluorimeter Flu oroMax-2. The ratiometric method (R340/380) was used as an index of [Ca2+]( i) change during smooth muscle contraction. All data, R340/380 and tension, were recorded using a computerized data acquisition system: Soft & Solutio n and GRAMS/386 of Galatic Industries Corporation.