ABSTRACT
The transient outward current I(to) is an important determinant of the early repolarization phase. I(to) and its molecular basis Kv4.3 are regulated by adrenergic pathways including protein kinase C. However, the exact regulatory mechanisms have not been analyzed yet. We here analyzed isoenzyme specific regulation of Kv4.3 and I(to) by PKC. Kv4.3 channels were expressed in Xenopus oocytes and currents were measured with double electrode voltage clamp technique. Patch clamp experiments were performed in isolated rat cardiomyocytes. Unspecific PKC stimulation with PMA resulted in a reduction of Kv4.3 current. Similar effects could be observed after activation of conventional PKC isoforms by TMX. Both effects were reversible by pharmacological inhibition of the conventional PKC isoenzymes (Gö6976). In contrast, activation of the novel PKC isoforms (ingenol) did not significantly affect Kv4.3 current. Whereas TMX-induced PKC activation was not attenuated inhibition of PKCß, inhibition of PKCα with HBDDE prevented inhibitory effects of both PMA and TMX. Accordingly, stimulatory effects of PMA and TMX could be mimicked by the α-isoenzyme selective PKC activator iripallidal. Further evidence for the central role of PKCα was provided with the use of siRNAs. We found that PKCα siRNA but not PKCß siRNA abolished the TMX induced effect. In isolated rat cardiomyocytes, PMA dependent I(to) reduction could be completely abolished by pharmacologic inhibition of PKCα. In summary we show that PKCα plays a central role in protein kinase C dependent regulation of Kv4.3 current and native I(to). These results add to the current understanding of isoenzyme selective ion channel regulation by protein kinases.
Subject(s)
Membrane Potentials/physiology , Myocytes, Cardiac/metabolism , Oocytes/metabolism , Protein Kinase C-alpha/metabolism , Shal Potassium Channels/metabolism , Signal Transduction , Animals , Carbazoles/pharmacology , Enzyme Inhibitors/pharmacology , Female , Isoenzymes/genetics , Isoenzymes/metabolism , Membrane Potentials/drug effects , Myocytes, Cardiac/cytology , Myocytes, Cardiac/drug effects , Oocytes/cytology , Oocytes/drug effects , Patch-Clamp Techniques , Plasmids , Protein Kinase C/genetics , Protein Kinase C/metabolism , Protein Kinase C beta , Protein Kinase C-alpha/genetics , Rats , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Shal Potassium Channels/genetics , Signal Transduction/drug effects , Substrate Specificity , Tetradecanoylphorbol Acetate/pharmacology , Transfection , XenopusSubject(s)
Angiotensin-Converting Enzyme Inhibitors/adverse effects , Antihypertensive Agents/adverse effects , Dermatitis, Occupational/etiology , Drug Eruptions/etiology , Hydrochlorothiazide/adverse effects , Photosensitivity Disorders/etiology , Ramipril/adverse effects , Sodium Chloride Symporter Inhibitors/adverse effects , Ultraviolet Rays/adverse effects , Welding , Diuretics , Humans , Male , Middle AgedABSTRACT
This article describes the perceived benefits of a quality improvement program, briefly discusses the steps involved in the establishment of such a program, and describes the implementation of a computer database for data collection and retrieval. The outcome of 4,500 anesthesia cases, representing 30 months of casework, is included. This article concludes with a discussion of the strengths and weaknesses of the program as well as a suggestion for future quality improvement endeavors.