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Protein kinase C regulates the tonic but not the phasic component of contraction in guinea‐pig ileum
Author(s) -
Sasaguri Toshiyuki,
Watson Stephen P.
Publication year - 1989
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.1476-5381.1989.tb14607.x
Subject(s) - carbachol , protein kinase c , protein kinase a , contraction (grammar) , phorbol , ileum , endocrinology , tonic (physiology) , medicine , muscle contraction , biology , chemistry , kinase , biochemistry , stimulation
1 We have investigated the effect of phorbol esters and the down‐regulation of protein kinase C on contraction of guinea‐pig ileum longitudinal smooth muscle to carbachol and high K + . 2 Phorbol 12,13‐dibutyrate (PDBu) enhanced the phasic component and inhibited or enhanced, respectively, the tonic component of contraction to carbachol and high K + . In contrast, 4α‐phorbol, which does not activate protein kinase C, had no effect on these responses. 3 Exposure to phorbol 12‐myristate 13‐acetate (PMA; 1 μ m ) for up to 8 h induced a time‐dependent loss of [ 3 H]‐PDBu binding sites, consistent with the down‐regulation of protein kinase C by this treatment. 4 The phasic component of contraction to carbachol or high K + was unaffected following the down‐regulation of protein kinase C. The tonic component of contraction to carbachol was markedly enhanced by this treatment while that to high K + was partially suppressed. 5 These data suggest that although the activation of protein kinase C can lead to potentiation of the phasic component of contraction to carbachol or high K + , this appears to have little physiological significance since the response is not altered in tissues in which protein kinase C has been down‐regulated. On the other hand, protein kinase C may limit the tonic contraction to carbachol but potentiate that to high K + .