Figure 8. Effect of CPA, caffeine and ryanodine, and preconstriction with 20 mM K⁺ on HPV in IPA.

A and B, IPAs were exposed to hypoxia in the presence of 3 μM PGF_2α (○) and following preincubation with 30 μM CPA (A, •, n= 5), or 10 μM ryanodine and 10 mM caffeine (B, ▪, n= 7). For CPA only, PGF_2α had to be reduced to 1 μM to maintain the same level of pretone as control. For ryanodine and caffeine no alteration from 3 μM PGF_2α was required. C, IPAs were exposed to hypoxia following preconstriction with 3 μM PGF_2α (○) or 20 mM K⁺ (□, n= 5). * P < 0.05, ** P < 0.001 compared to control.