Figure 5. Effect of phorbol ester (PDBu) on contractile force in mesenteric arteries.

Time course of contractile effect of 1 μm PDBu following high K⁺-induced contraction in intact rabbit (A), chicken (B) and pigeon MA (C). Na, normal extracellular solution; K, high (154 mm)-K⁺ solution. Middle panel, effect of 1 μm PDBu on Ca²⁺-induced contraction in α-toxin-permeabilized rabbit (D), chicken (E) and pigeon MA (F). Height of pCa 4.5-induced contraction represents a maximal force in each arterial strip. Bottom panel (n = 4), control contractile Ca²⁺ sensitivity (○) and effect of 1 μm PDBu (•) in rabbit (G), chicken (H) and pigeon MA (I).