ROLE OF PROTEIN KINASE C IN REGULATION OF CARDIAC L-TYPE Ca^<2+> CHANNELS.

用细胞贴附式膜片钳技术记录了心肌L型钙通道的单通道活动，并对这些记录进行了分析，证实这些记录完全适用于本研究，目的是确定心肌蛋白激酶C(PKC)是否参与心脏L型钙通道的调节。通道活动，结果与报道的数据一致，表明没有影响宏观钙电流，这是通过全细胞膜片钳技术记录的。内皮素-1(ET-1)在激活心脏ET受体后，通过PIP_2水解酶激活PKC，但对单个Ca~(2+)&Gt~(2+)通道活动无明显影响。这些因素清楚地表明，心肌PKC的激活即使是直接或间接通过受体机制发生的。对L型钙离子通道的瞬时调节不敏感。不同于cAMP-A激酶系统。这些发现与这样一个事实相矛盾，即ET-1能够在豚鼠心房中建立一种可抑制的、硝苯地平敏感的正性变力作用的PKC抑制剂(H-7)。PKC的激活，不是瞬时的，而是通过细胞内信号转导过程的长期途径，可能通过抑制去磷酸化或重新激活睡眠中的钙通道来调节1型钙通道。

Recordings of single channel activities of cardiac l-type Ca^<2+> channels using a cell-attached patch clamp technique, and subsequent analvses of the recordings were confirmed to be sufficiently applicable to the present study aiming to determine whether cardiac protein kinase C( PKC) participates in regulating cardiac L-type Ca^<2+> channels.The present study using isolated rabbit ventricular myocytes revealed that 12-0-tetradecanoyl phoorbol-13-acetate(TPA), a direct activator of PRC.did not affect single Ca^<2+> channel activities, the result being consistent with the reported data showing no influence on macroscopic Ca2+ currents which was recorded by means of a whole-cell patch clamp technique. Endothelin-1(ET-1) which is known to activate PKC through PIP_2 hydrolvsis after activation of cardiac ET receptors, was also found not to givesignificant influence on the single Ca^<2+> channel activities.These facls cleary indicate that activation of cardiac PKC.even if it occurs directly or indirecily through a receptor mechanism. is not rsponsible to instantaneous regulation of L-type Ca^<2+> channels. differing from the cAMP-A kinase system.However. these findings contradict the fact that ET-1 is able to establish a PKC inhibitor(H-7, sta urosporine)-suppressible, nifedipine-sensitive delayd pnase of positive inotropic effect in guiea pig atria.PKC activation, not instantaneously but through a long range pathway of intracellular signal transducing process, may have a role in regulating 1-type Ca^<2+> channels by either inhibition of dephosphrylation or recruitement of sleeping Ca2+ channels.