Intercellular Ultrafast Calcium Wave Velocity And Propagation Of Spontaneous Electrical Activity In A7r5 Cells At Physiological Temperature

Temperature has pervasive effects on the functional properties of biological systems. In particular, mechanical performance and membrane conductance of muscles are greatly influenced by temperature. Experiments using an aligned micropatterned configuration of smooth muscle cells (A7r5) were performed at 37°C. Fluorescence microscopy revealed that both, mechanical and KCl stimulation, evoked an ultrafast Ca2+ wave with a velocity magnitude of almost two times the one obtained previously at room temperature and that is in agreement with the velocity reported previously by theoretical simulations (∼333 cells/s). On the other hand, cultured A7r5 cells showed spontaneous electrical activity exhibiting similarities with action potentials. In order to investigate the direction and velocity of propagation of this spontaneous activity, we used optical mapping of transmembrane voltage that allowed the characterization of patterns of electrical activity in A7r5 cultures at 37°C, at which temperature preparation had a high probability to exhibit spontaneous electrical activity. The optically measured spatial and temporal characteristics of propagating “action potentials” revealed, that in patterned strands of A7r5 cells, conduction velocity was not statistically different from the velocities of the ultrafast Ca2+ wave at 37°C (∼29 mm/s). Together, our results suggest a direct correlation between the speed of ultrafast Ca2+ wave/spreading velocity of the membrane depolarization with the speed of the phenomena known as electrical slow waves and also validate the numerical data reported with experiments at physiological temperatures. The ultrafast Ca2+ wave and the spontaneous electrical activity may trigger slower Ca2+ waves observed ex vivo and in vivo in smooth muscle cells.