Fig. 1.

Improved basal contractile shortening of the binary P2X₄ receptor (P2X₄R)/calsequestrin (CSQ) cardiac myocyte. A: representative traces of contractile or cell shortening (CS) at 0.2 Hz in myocytes from 12-wk-old wild-type (WT), P2X₄ transgenic (Tg), CSQ Tg, and binary Tg hearts were shown. Data were typical of 41 myocytes from 20 WT mice, 59 myocytes of P2X₄R Tg, 60 myocytes from 33 CSQ mice, and 54 myocytes from 32 binary mice. CS traces were superimposed for WT and P2X₄R Tg as well as for CSQ and binary myocytes in right column. Binary myocytes showed a greater peak CS and a shorter duration of contraction at 0.2 Hz. Average of CS, expressed as percentage of cell length, was shown for myocytes paced at 0.2 Hz (B) or at 1.0 Hz (C). Data and SE were presented. Maximal CS in binary cardiac myocytes was greater than that in CSQ cardiac myocytes (P < 0.05) at both stimulation frequencies. **P < 0.05 when compared with either WT or P2X₄ Tg by 1-way ANOVA followed by posttest comparison.