Inhibition of phorbol ester-induced contraction by calmodulin antagonists in rat aorta.
The purpose of the present study was to investigate the relative roles of protein kinase C (PKC) and myosin light chain kinase (MLCK) in phorbol ester-induced contraction of vascular smooth muscle through the use of PKC and calmodulin antagonists. Prior exposure to PKC antagonists staurosporine (0.03 microM) and H-7 (10 microM) had relatively little effect on contractions to phorbol 12-myristate 13-acetate (PMA), while contractions to norepinephrine and KCl were greatly inhibited. Prior exposure to the calmodulin antagonists calmidazolium (3 and 10 microM) and W-7 (10 microM) inhibited contractions to PMA in the presence and absence of extracellular Ca2+, while contractions to norepinephrine and KCl remained relatively unaffected. Calmidazolium and W-7 were relatively weak relaxants when applied during the PMA contraction, and the magnitudes of relaxation were similar to those observed in norepinephrine- and KCl-contracted tissues. Calmidazolium partially inhibited the PMA-induced translocation of PKC. These results suggest that 1) the calmodulin antagonists inhibit the development of PMA-induced contraction, at least in part, through inhibition of PKC translocation; 2) the mechanisms of phorbol ester- and agonist-induced translocation of PKC are distinct; 3) the potencies and inhibitory mechanisms of these agents depend on whether the agents are added before or during the contraction; and 4) the selectivity of these agents, as evaluated in enzyme preparations, may not be consistent with their cellular actions.
Chuprun
J K
JK
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0575.
Bazan
E
E
Chang
K C
KC
Campbell
A K
AK
Rapoport
R M
RM
D000818:Animals; D001011:Aorta / Q000187:drug effects*; D002118:Calcium / Q000502:physiology; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D007093:Imidazoles / Q000494:pharmacology*; D007552:Isotonic Solutions / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D011919:Rats, Inbred Strains; D013449:Sulfonamides / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects*
D002147:Calmodulin; D007093:Imidazoles; D007552:Isotonic Solutions; C051865:Krebs-Ringer solution; D013449:Sulfonamides; C031938:calmidazolium; C017967:W 7; D011189:Potassium Chloride; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D009638:Norepinephrine