Knox A J, Baldwin D R, Cragoe E J, Ajao P
Respiratory Medicine Unit, City Hospital, Nottingham, UK.
Pulm Pharmacol. 1993 Dec;6(4):241-6. doi: 10.1006/pulp.1993.1032.
We studied the role of sodium transport and calcium channels in protein kinase C mediated signal-transduction pathways in bovine airway smooth muscle. 4-beta phorbol 12,13 dibutyrate (PDB), an activator of protein kinase C, caused dose-related slowly developing contraction in bovine bronchial rings with a peak effect at 60-90 min. 4-alpha PDB, an inactive analogue, was without effect. Mean peak PDB-induced contraction (measured as a percentage of the maximum response to methacholine) was reduced from 122% to 20% when experiments were carried out in calcium-free fluids +EDTA (10(-3) M). Similar reductions were seen in the presence of nifedipine and verapamil, inhibitors of voltage-dependent calcium channels. Amiloride at high concentrations (10(-3) M) reduced the contractile response to PDB from 87% to 20%, but at a concentration which inhibits the sodium entry channel (10(-6) M), amiloride was without effect. 5-N,N-hexamethylene amiloride (10(-5) M), a specific inhibitor of Na+/H+ exchange, did not alter the contraction produced by PDB. Frusemide (10(-5) M), an inhibitor of Na(+)-K(+)-Cl- cotransport, was without effect on PDB contractions. We conclude that phorbol ester-induced contraction of bovine airway smooth muscle is dependent on calcium entry via voltage-dependent calcium channels but is independent of Na+ entry, Na+/H+ exchange or Na(+)-K(+)-Cl- cotransport.
我们研究了钠转运和钙通道在牛气道平滑肌中蛋白激酶C介导的信号转导途径中的作用。蛋白激酶C的激活剂4-β佛波醇12,13-二丁酸酯（PDB）可引起牛支气管环剂量相关的缓慢发展的收缩，在60-90分钟时达到峰值效应。无活性类似物4-αPDB则无作用。当在无钙溶液+EDTA（10⁻³M）中进行实验时，PDB诱导的平均峰值收缩（以对乙酰甲胆碱最大反应的百分比衡量）从122%降至20%。在电压依赖性钙通道抑制剂硝苯地平和维拉帕米存在的情况下也观察到类似的降低。高浓度（10⁻³M）的氨氯地平将对PDB的收缩反应从87%降至20%，但在抑制钠进入通道的浓度（10⁻⁶M）下，氨氯地平无作用。5-N,N-六亚甲基氨氯地平（10⁻⁵M），一种Na⁺/H⁺交换特异性抑制剂，并未改变PDB产生的收缩。呋塞米（10⁻⁵M），一种Na⁺-K⁺-Cl⁻共转运抑制剂，对PDB收缩无作用。我们得出结论，佛波酯诱导的牛气道平滑肌收缩依赖于通过电压依赖性钙通道的钙内流，但与Na⁺内流、Na⁺/H⁺交换或Na⁺-K⁺-Cl⁻共转运无关。
