Fig. 5.

PC2 required for maintenance the Ca²⁺ content in the SR stores. (a) Representative traces of Ca²⁺ transients in Pkd2^+/+ and Pkd2^−/− cardiomyocytes. Ca²⁺ transients were induced by application of 5 μM thapsigargin to the EGTA-buffered Ca²⁺-free extracellular solution. (b) Ca²⁺ content in the SR store. F/F₀ was determined as described in Materials and Methods. Pkd2^−/− mouse cardiomyocytes have a decreased Ca²⁺ content in the SR store. Statistical significance was calculated by using a one-tailed t test: ∗∗, P < 0.001 (n = 40 for Pkd2^+/+; n = 40 for Pkd2^−/−). (c) Duration of Ca²⁺ transient in Pkd2^+/+ and Pkd2^−/− cardiomyocytes. There was no difference in the duration of Ca²⁺ transients (n = 17 for Pkd2^+/+ and n = 23 for Pkd2^−/− cardiomyocytes). (d) SERCA-2a has similar expression levels in Pkd2^+/+ and Pkd2^−/− mouse cardiomyocytes. Tissue lysates were prepared from mouse heart at embryonic day 17.5 as described in Materials and Methods.