The effect of Ca2+ on the translocation of protein kinase C in bovine tracheal smooth muscle.
The role of calcium in protein kinase C redistribution was studied in bovine tracheal smooth muscle preparations contracted by methacholine. Previous results have shown that, in the presence of normal extracellular Ca2+, 10 microM methacholine produced a sustained contraction and a sustained translocation of protein kinase C from the cytosol to the membrane. In the present study, when tissues were preincubated in Ca(2+)-free buffer containing 1 mM EGTA, methacholine produced a rapid but transient elevation in membrane-associated protein kinase C activity which was detected at 30 s and had returned to basal within 20 min. The redistribution of protein kinase C from the cytosol to the membrane induced by 1 microM methacholine in normal Ca2+ was reversed by removal of the extracellular Ca2+ and addition of 2 mM EGTA during agonist stimulation. Removal of the Ca2+ caused approximately 50% relaxation after 10 min. Verapamil (30 microM) partially reversed the methacholine-induced protein kinase C redistribution and caused approximately 40% relaxation after 15 min. Sodium nitroprusside (10 microM) caused a rapid relaxation and complete reversal of the protein kinase C redistribution induced by methacholine. High K+ (60 mM) also induced a sustained contraction and redistribution of protein kinase C from the cytosol to the membrane. Suitable antagonists were added to the bathing medium to block the effects of endogenous mediators which could be released by KCl-induced depolarization. Thus, translocation of protein kinase C is obtained in the absence of receptor activation.(ABSTRACT TRUNCATED AT 250 WORDS)
Langlands
J M
JM
Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada.
Diamond
J
J
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002417:Cattle; D003600:Cytosol / Q000201:enzymology; D016210:Methacholine Chloride / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000201:enzymology; D009543:Nifedipine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D014132:Trachea / Q000187:drug effects / Q000201:enzymology; D014700:Verapamil / Q000494:pharmacology
D016210:Methacholine Chloride; D009599:Nitroprusside; D014700:Verapamil; D011493:Protein Kinase C; D009543:Nifedipine; D011188:Potassium; D002118:Calcium