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Effect of phorbol ester and pertussis toxin on the enhancement of noradrenaline release by angiotensin II in mouse atria
Author(s) -
Musgrave Ian F.,
Majewski Henryk
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.tb11859.x
Subject(s) - pertussis toxin , angiotensin ii , toxin , chemistry , pharmacology , phorbol ester , endocrinology , medicine , biology , g protein , biochemistry , protein kinase c , receptor , signal transduction
1 Mouse atria were incubated with [ 3 H]‐noradrenaline, and the outflow of radioactivity due to electrical field stimulation (5 Hz, 60 s) was used as an index of noradrenaline release. Angiotensin II (0.01 and 0.1 μ m ) significantly enhanced the stimulation‐induced (S‐I) outflow of radioactivity. 2 Phorbol 12‐myristate 13‐acetate (0.001, 0.03, 0.1 and 1.0 μ m ), a protein kinase C activating phorbol ester, significantly enhanced the S‐I outflow of radioactivity. When angiotensin II (0.1 μ m ) was present with the concentration of phorbol 12‐myristate 13‐acetate that was maximally effective in increasing the S‐I outflow (0.1 μ m ), the enhancement of S‐I outflow produced by angiotensin II was maintained. 3 Polymyxin B (70 μ m ), an inhibitor of protein kinase C, significantly inhibited the S‐I outflow. Polymyxin B also inhibited the enhancement of the S‐I outflow produced by angiotensin II (0.1 μ m ). 4 In another series of experiments mice were injected with pertussis toxin (1.5 μg per mouse), 4 days before their atria were removed. The effectiveness of pertussis toxin pretreatment was determined indirectly using carbachol. Carbachol caused a concentration‐dependent fall in both the rate and force of beating of isolated spontaneously beating atria from mice pretreated with vehicle. This effect of carbachol was not seen with atria from mice pretreated with pertussis toxin. 5 Pertussis toxin pretreatment did not alter the enhancement of the S‐I outflow of radioactivity produced by angiotensin II (0.01 and 0.1 μ m ). 6 These results suggest that angiotensin II receptor modulation of noradrenaline release is not mediated through either a pertussis toxin sensitive guanine nucleotide‐binding protein or activation of protein kinase C.