Chik C L, Li B, Ogiwara T, Ho A K, Karpinski E
Department of Medicine, University of Alberta, Edmonton, Canada.
FASEB J. 1996 Sep;10(11):1310-17. doi: 10.1096/fasebj.10.11.8836045.
The effect of pituitary adenylate cyclase activating polypeptide (PACAP) on the L-type Ca2+ channel current (L-channel current) was studied in smooth muscle cells prepared from the rat tail artery. PACAP caused an increase in the amplitude of the L-channel current. The maximal increase (56%) occurred at a PACAP concentration of 1 x 10(-8) M; higher concentrations resulted in a smaller increase. Investigation into the intracellular mechanisms of PACAP action revealed that the increase in L-channel currents was blocked by calphostin C and bisindolylmaleimide IV [protein kinase C (PKC) inhibitors] and mimicked by 4 beta-phorbol 12-myristate 13-acetate (PMA), an activator of PKC. PACAP was also found to cause translocation of PKC, suggesting that the increase in the current by PACAP was due to PKC. In contrast, activation of cAMP-dependent protein kinase (PKA) by 8-bromo-cAMP caused an inhibition of the L-channel current. A high concentration of PACAP (1 x 10(-6) M) had no effect on the L-channel current. The null effect of PACAP on the L-channel current could be converted to an increase by Rp-cAMPs, a cAMP antagonist, and a decrease by calphostin C. PACAP also increased cAMP accumulation. These observations indicate the effect of PACAP on the L-channel current represents the integration of two signaling mechanisms that involve the activation of PKA and PKC.
在从大鼠尾动脉制备的平滑肌细胞中研究了垂体腺苷酸环化酶激活多肽（PACAP）对L型钙通道电流（L通道电流）的影响。PACAP使L通道电流的幅度增加。最大增加量（56%）出现在PACAP浓度为1×10⁻⁸ M时；更高的浓度导致较小的增加。对PACAP作用的细胞内机制的研究表明，L通道电流的增加被钙泊三醇C和双吲哚马来酰亚胺IV[蛋白激酶C（PKC）抑制剂]阻断，并被PKC激活剂4β-佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）模拟。还发现PACAP导致PKC易位，表明PACAP引起的电流增加是由于PKC。相反，8-溴-cAMP激活cAMP依赖性蛋白激酶（PKA）会抑制L通道电流。高浓度的PACAP（1×10⁻⁶ M）对L通道电流没有影响。PACAP对L通道电流的无效作用可通过cAMP拮抗剂Rp-cAMPs转化为增加，而被钙泊三醇C转化为减少。PACAP还增加了cAMP的积累。这些观察结果表明，PACAP对L通道电流的影响代表了涉及PKA和PKC激活的两种信号传导机制的整合。
