Figure 1

Prolonged incubation of tracheal epithelial cells in buffer solutions did not change [Ca²⁺]_i. (A) The [Ca²⁺]_i was indicated by a FURA-2 ratio of 340 nm/380 nm. As a control, isolated tracheal epithelial cells were kept under long-term incubation in Ca²⁺-containing 2.5 mM buffer. During this prolonged incubation period, the basal [Ca²⁺]_i did not change. The vitality test at the end of each experiment was carried out by applying KCl (200 mM), inducing a rapid Ca²⁺-influx and an increase in [Ca²⁺]_i. (B) The initial levels of [Ca²⁺]_i had not changed when they were briefly measured at the end of the exposure period before the application of KCl. (C) The prolonged incubation of tracheal epithelial cells in Ca²⁺-free buffer solution did not change the [Ca²⁺]_i. The application of KCl (200 mM, containing 2.5 mM CaCl₂) precipitated an increase in [Ca²⁺]_i. (D) In the Ca²⁺-free buffer solution, the initial [Ca²⁺]_i also did not change when it was briefly measured at the end of the exposure period before the KCl application (n = number of individual experiments, ns = not significant, Wilcoxon rank-sum test).