FIGURE 6.

UTP stimulation of P2Y₂-R slowed proteolytic stimulation of ENaC. UTP (10 μm) was included in the chymotrypsin containing perfusate. Tau was calculated as described in Fig. 2. UTP also slowed proteolytic activation when the K-cluster in the γNT was mutated to arginines (γNT-5K/R) to preserve basic charge. However, mutation of the γNT K-cluster to glutamines (γNT-5K/Q) caused slower stimulation of I_Na that was not affected by UTP in oocytes coexpressing P2Y₂-R (n = 12–14 for each experimental group, one-way analysis of variance; *, p < 0.05; ***, p < 0.005)).