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The influence of activation or inhibition of protein kinase C on the release of radioactivity from rat isolated atria labelled with [ 3 H]‐noradrenaline
Author(s) -
Ishac Edward J.N.,
Luca Anthony
Publication year - 1988
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.1476-5381.1988.tb11580.x
Subject(s) - chemistry , pharmacology , protein kinase c , biochemistry , kinase , biology
1 The release of radioactivity from rat isolated atria preloaded with [ 3 H]‐noradrenaline ([ 3 H]‐NA) evoked by electrical field stimulation (2Hz, 1 ms, 60s) of intraneuronal sympathetic nerves, high potassium (64.7 m m ) or tyramine (0.3μm) was used as an index of noradrenaline release. 2 Activation of protein kinase C by phorbol 12‐myristate 13‐acetate (PMA) produced a concentration‐dependent enhancement of field stimulation‐induced outflow of radioactivity, whereas polymyxin B, an inhibitor of protein kinase C, reduced [ 3 H]‐NA release evoked by field stimulation. The enhancement observed in the presence of PMA was attenuated by polymyxin B (10 and 70 μm). 3 Release of noradrenaline evoked by membrane depolarization in a high potassium medium was similarly affected by PMA and polymyxin B. 4 In contrast, the release of noradrenaline evoked by the indirectly acting sympathomimetic amine, tyramine, was not altered by PMA. Polymyxin B in a concentration of 70 μ m , but not 10 μ m caused a slight reduction in tyramine‐induced outflow of radioactivity. 5 The spontaneous outflow of radioactive compounds was not affected by either PMA or polymyxin B in the bathing medium. 6 The findings suggest that protein kinase C may play a role in the exocytotic release of noradrenaline but not in the displacement of noradrenaline by indirectly acting sympathomimetic amines.