P2RX7 and atrial fibrillation: In contrast, acute exposure of AF cells to CTS at 2.0 Hz significantly upregulated the expression of the transient receptor potential vanilloid 4 (Trpv4) gene at 12 hours postloading (fold change = 1.9 ± 0.34), with a trend towards increased purinoreceptor x subtype 7 (P2rx7) gene expression 2 hours postloading (fold change = 1.3 ± 0.14), compared to unloaded controls (Figure 9C).