Improved kinetic analysis of cytosolic free calcium in pressure-sensitive neuronal cells by fixed-time flow cytometry

Two flow cytometric techniques were used to measure rapid transient changes in [Ca2+] in the neuronal cell line NH15-CA2. Using on-line injection, the cell suspension and stimulating solution are mixed and delivered to the detection point by a rapid increase in sample pressure. In NH15-CA2, injection of medium alone resulted in [Ca2+]i increase. Using the fixed-time method, where cells are maintained at constant pressure, no [Ca2+ ]i, increase was observed with medium alone. These results show that a rapid pressure increase alone alters the [Ca2+]i in NH15-CA2 cells. Both methods showed similar kinetics of [Ca2+], in response to bradykinin but the fixed-time method was found to be better for determination of the percentage of responsive cells.