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Relaxation of guinea‐pig trachea by sodium nitroprusside: cyclic GMP and nitric oxide not involved
Author(s) -
SadeghiHashjin Gudarz,
Folkerts Gert,
Henricks Paul A.J.,
Loo Peet G.F.,
Dik Ilse E.M.,
Nijkamp Frans P.
Publication year - 1996
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.1476-5381.1996.tb15426.x
Subject(s) - sodium nitroprusside , guinea pig , nitric oxide , cyclic gmp , relaxation (psychology) , chemistry , sodium , medicine , pharmacology , biophysics , anesthesia , nuclear magnetic resonance , biology , physics , organic chemistry
1 Sodium nitroprusside (SNP) completely relaxed the guinea‐pig isolated, perfused trachea in a concentration‐dependent manner. Although SNP was less potent by about 2 orders of magnitude, its maximal effect was 25% higher compared to isoprenaline. 2 SNP (3.2 μ m ) increased cyclic GMP levels by 300% and relaxed guinea‐pig isolated, perfused trachea by 54%. The SNP‐induced relaxations of the preparations were not affected by the guanylate cyclase inhibitor, methylene blue. Moreover, zaprinast, a cyclic GMP‐specific phosphodiesterase inhibitor which was supposed to enhance SNP‐induced relaxations, decreased the maximal relaxation by 22% ( P < 0.001). 3 In contrast, 8Br‐cyclic GMP (10 μ m ) increased the cyclic GMP levels by 1100% without inducing a marked relaxation. 4 SNP (10 μ m ) and S ‐nitroso‐ N ‐acetylpenicillamine (SNAP; a direct donor of nitric oxide; 10 μ m ), relaxed the tissues by 75% and 25%, respectively, without any nitric oxide (NO) release by SNP (< 1 pmol 100 μl −1 ), but a substantial NO release by SNAP (560 pmol 100 μl −1 ). 5 It is concluded that the SNP‐induced tracheal relaxations are probably not mediated by cyclic GMP and NO.