Figure 6.

Spontaneous cilia activity is not dependent on Ca²⁺ or on Ca²⁺–calmodulin complex. (A) CBF measurements from two different cells before and following whole-cell formation (indicated by arrow). The cells were superfused with the standard extracellular solution at 32°C and voltage clamped at −40 mV. The pipette solution contained (in mM): CsCl 148, EGTA 1, TES 5, MgATP 5, K₂ATP 0.5, adjusted to pH 7.2 with CsOH. In addition, intracellular Ca²⁺ was adjusted to either 500 nM (left) or <1 nM (right). (B) Mean (±SEM) CBF measured from single isolated ciliated cells before (open boxes) and 10 min after establishing the whole-cell configuration (full boxes). Intracellular Ca²⁺ was adjusted to: <1, 100, or 500 nM, as indicated (left). There is no significant difference in CBF before and after establishing the whole-cell configuration (Student's t test). The numbers of experiments are indicated above the bars. The addition of 100 μg/ml calmodulin to the intracellular solution adjusted to contain 1 μM Ca²⁺ failed to enhance cilia beating (middle). In some experiments, both the bath and pipette solutions contained less than 1 nM Ca²⁺, yet spontaneous beating was unaffected (right).