FIGURE 1.

The absence of PMCA4 in the heart had no effect on global calcium extrusion. A, Western blot showing PMCA4 deletion in cardiac tissue from PMCA4^−/− mice. B, immunostaining of isolated single cardiomyocytes to verify efficiency of the deletion of PMCA4. Alexa Fluor 594 phalloidin was used to stain the F-actin to identify cardiomyocytes. C, representative Western blots to detect the expression of PMCA1, L-type calcium channel, SERCA2, and NCX in heart extracts from PMCA4^−/− mice. D, representative traces of calcium decay following application of Na⁺/Ca²⁺ free solution (to completely inhibit the Na⁺/Ca²⁺ exchanger) in the presence of 10 mm caffeine (to empty the sarcoplasmic reticulum). E, quantification of the time constant of the Ca²⁺ decay (τ) suggested that Ca²⁺ efflux through PMCA is not impaired in the PMCA4^−/− cardiomyocytes, which indicates the negligible contribution of PMCA4 to global calcium extrusion (n = 6).