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.
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0575.
J K
JK
Chuprun
E
E
Bazan
K C
KC
Chang
A K
AK
Campbell
R M
RM
Rapoport
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