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Sensitivity to protein kinase C inhibitors of nicardipine‐insensitive component of high K + contracture in rat and guinea‐pig aorta
Author(s) -
Low A.M.,
Loke J.C.P.,
Kwan C.Y.,
Daniel E.E.
Publication year - 1994
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1994.tb13117.x
Subject(s) - contraction (grammar) , calphostin c , nicardipine , cyclopiazonic acid , channel blocker , nifedipine , chemistry , phenylephrine , egta , verapamil , endocrinology , muscle contraction , medicine , thapsigargin , biophysics , calcium , extracellular , biochemistry , protein kinase c , biology , kinase , blood pressure
1 In the rat and guinea‐pig aorta, we observed that the contraction to hypertonically‐added K + , unlike the isotonic K + ‐induced contraction, was only partially sensitive to nicardipine (0.1, 1 and 10 μ m ), an L‐type Ca 2+ channel blocker and occurred in Ca 2+ ‐free medium containing 50 μ m EGTA. We have characterized this nicarpidine‐insensitive hypertonically‐added K + contraction. 2 The contraction induced by an equi‐osmolar concentration of mannitol was similar in size to that evoked by hypertonically‐added K + . 3 When the tissue was depleted of its internal Ca 2+ stores with various agents such as phenylephrine (10 μ m ), cyclopiazonic acid (30 μ m ), thapsigargin (1 μ m ) or ryanodine (30 μ m ), or by incubation in Ca 2+ ‐free medium over 30 min, little effect was observed on the high K + contracture in the presence of L‐type Ca 2+ channel blockade. 4 Phentolamine (10 μ m ) or indomethacin (10 μ m ) did not reduce the contraction induced by high K + . 5 Application of a protein kinase C inhibitor, H7 (10, 30 and 100 μ m ) or calphostin C (1 μ m ), reduced the high K + contraction but not that caused by an equi‐osmolar concentration of mannitol. 6 The data suggest that hypertonic K + ‐induced contraction differs from that caused by hypertonicity or depolarization per se and invokes membrane enzyme activation.