Fig. 3.

Ca²⁺ signaling is impaired in InsP₃R2 KO hepatocytes. (A) Representative tracing of Fluo4 fluorescence changes over time in WT and InsP₃R2 KO hepatocytes stimulated with ATP (100 μM). Hepatocytes were stimulated with either ATP or AVP and examined by time-lapse confocal microscopy. Using these individual tracings, the amplitude and the rise time of the Ca²⁺ signal from individual hepatocytes was determined. (B) The increase in Ca²⁺ induced by AVP (10 nM) was greater in WT as compared with InsP₃R2 KO hepatocytes (165 ± 3%, n = 309 cells versus 148 ± 2%, n = 423 cells; P < 0.0001). (C) ATP (100 μM)-induced Ca²⁺ release also was greater in WT as compared with InsP₃R2 KO cells (152.9 ± 1.16%, n = 149 versus 146.2 ± 1.18%, n = 176; P < 0.001). (D) Rise time of Ca²⁺ signal was faster in WT hepatocytes than in InsP₃R2 KO cells perfused with AVP 10 nM (11.43 ± 0.71 seconds, n = 251 versus 29.96 ± 1.30 seconds, n = 256; P < 0.0001). (E) Rise time also was shorter in WT than in InsP₃R2 KO cells when ATP 100 μM was used to induced Ca²⁺ release (1.89 ± 0.08 seconds, n = 149 cells versus 2.81 ± 0.17 seconds, n = 176 cells; P < 0.0001), reflecting slower Ca²⁺ release in cells lacking InsP₃R2.