Itoh T, Kanmura Y, Kuriyama H, Sumimoto K
J Physiol. 1986 Jun;375:515-34. doi: 10.1113/jphysiol.1986.sp016131.
To clarify the role of protein kinase C in the mechanical response, the effects of 12-o-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, were investigated on intact and skinned smooth muscle preparations of the rabbit mesenteric artery. TPA (0.1 microM) showed dual actions (initial enhancement followed by inhibition during long exposure) on the K+-induced contraction. The enhancement was marked in the presence of 39 mM-K+ but inhibition was the predominant effect in the presence of 128 mM-K+. Addition of 2.6 mM-Ca2+ to a Ca2+-free solution containing 2 mM-EGTA following application of A23187 (1 microM), produced contraction. TPA showed the same dual actions on this Ca2+-induced contraction. In chemically skinned muscles, TPA increased the amplitude of Ca2+-induced contractions evoked by low concentrations of Ca2+ (0.1-0.3 microM), but reduced those evoked by high concentrations of Ca2+ (1-10 microM). Both actions of TPA were facilitated in the presence of phosphatidylserine (PS). TPA with PS had no effect on the Ca2+-independent contraction evoked in relaxing solution containing 10 mM-EGTA and 4 mM-Mg ATP following application of adenosine-5-o-3-thiotriphosphate (ATP gamma S) and 0.3 microM-Ca2+. The amount of Ca2+ stored in cells estimated from the amplitude of the caffeine-induced contraction was not modified by application of TPA with PS in skinned or intact muscle tissues. The effects of TPA were investigated on the Ca2+ transient measured from the intensity of fluorescence of quin-2 in dispersed cell suspensions prepared from the porcine coronary artery. TPA had no effect on the Ca2+ transient in high K+ but enhanced the amplitude of the contraction. Amplitudes of the tonic response evoked by 39 mM-K+ in intact muscle tissues and the contraction induced by 0.3 microM-Ca2+ in skinned muscle were much the same. TPA with PS enhanced the amplitudes of both contractions to the same extent. From the above results, we concluded that TPA shows dual actions on the contractile machinery and may act on the regulatory systems of contractile proteins. Both excitatory and inhibitory actions of TPA depended on the concentration of Ca2+. However, the physiological action of protein kinase C as estimated from the action of TPA seems to be related to an excitatory action on the contractile machinery.
为阐明蛋白激酶C在机械反应中的作用，研究了蛋白激酶C激活剂12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）对兔肠系膜动脉完整和去膜平滑肌标本的影响。TPA（0.1微摩尔）对钾离子诱导的收缩呈现双重作用（初始增强随后在长时间暴露时抑制）。在39毫摩尔钾离子存在时增强作用明显，但在128毫摩尔钾离子存在时抑制作用占主导。在应用A23187（1微摩尔）后，向含有2毫摩尔乙二醇双四乙酸（EGTA）的无钙溶液中添加2.6毫摩尔钙离子会产生收缩。TPA对这种钙离子诱导的收缩也表现出相同的双重作用。在化学去膜肌肉中，TPA增加了低浓度钙离子（0.1 - 0.3微摩尔）诱发的钙离子诱导收缩的幅度，但降低了高浓度钙离子（1 - 10微摩尔）诱发的收缩幅度。TPA的这两种作用在磷脂酰丝氨酸（PS）存在时均得到促进。在应用腺苷 - 5 - O - 3 - 硫代三磷酸（ATPγS）和0.3微摩尔钙离子后，含有10毫摩尔EGTA和4毫摩尔镁 - ATP的松弛溶液中诱发的与钙离子无关的收缩，TPA与PS对此无影响。在去膜或完整肌肉组织中，根据咖啡因诱导收缩的幅度估算的细胞内钙离子储存量，不受TPA与PS应用的影响。研究了TPA对从猪冠状动脉制备的分散细胞悬液中喹啉 - 2荧光强度测量的钙离子瞬变的影响。TPA在高钾条件下对钙离子瞬变无影响，但增强了收缩幅度。完整肌肉组织中39毫摩尔钾离子诱发的强直反应幅度与去膜肌肉中0.3微摩尔钙离子诱导的收缩幅度大致相同。TPA与PS同等程度地增强了两种收缩的幅度。根据上述结果，我们得出结论，TPA对收缩机制呈现双重作用，可能作用于收缩蛋白的调节系统。TPA的兴奋和抑制作用均取决于钙离子浓度。然而，从TPA的作用估算的蛋白激酶C的生理作用似乎与对收缩机制的兴奋作用有关。
