Fig. 5. CAP_2b-induced cytosolic calcium signals in itpr mutants. (A) Typical traces of changes in intracellular Ca²⁺ concentration ([Ca²⁺]_i) in tubule principal cells stimulated by 10^-7 moll^-1 CAP_2b (arrows) in the following lines: (i) aeq;hsGAL4;+ (control), (ii) aeq;hsGAL4;itpr^XR12/+, (iii) aeq;hsGAL4;itpr^90B.0/+, (iv) aeq;hsGAL4;itpr¹⁶⁶⁴/+, (v) aeq;hsGAL4;itpr¹⁶⁶⁴/itpr¹⁶⁶⁴ and (vi) aeq;hsGAL4;itpr^WC361/itpr^UG3. Each sample contains 20 intact tubules. While no changes in the resting [Ca²⁺]_i is seen in any of the mutants, changes in amplitude of the primary and/or secondary response can be observed in all lines (also in B). (B) Pooled results of changes in tubule [Ca²⁺]_i in itpr mutants in response to 10^-7 moll^-1 CAP_2b are shown. Results are expressed as means ± S.E.M. (N=8) for background (open bars), CAP_2b-stimulated primary peaks (filled bars) and CAP_2b-stimulated secondary peaks (hatched bars) for the lines described in A. The measure of secondary peak is taken as the average [Ca²⁺]_i over 4 min post-stimulation with CAP_2b. CAP_2b-stimulated primary peaks that are significantly different from aeq;hsGAL4 tubules are denoted by ^*, and statistically significant differences in secondary peaks compared to wild type are denoted by (P<0.05, Student's t-test, unpaired samples).