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Nitroglycerine‐induced biphasic relaxation in vascular smooth muscle of rat aorta
Author(s) -
Karaki H.,
Murakami K.,
Nakagawa H.,
Urakawa N.
Publication year - 1984
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.1476-5381.1984.tb10090.x
Subject(s) - aorta , vascular smooth muscle , medicine , cardiology , anatomy , chemistry , smooth muscle
1 Nitroglycerine induced biphasic relaxation in the rat aorta, previously contracted by noradrenaline; a rapid decrease in tension was followed by a gradual increase reaching a steady level below the control contractile tension. No initial transient relaxation was induced by nitroglycerine in high K‐stimulated muscle. 2 The initial transient relaxation, but not the sustained relaxation, was dependent on the concentration of external K; maximum relaxation was observed in the presence of 2.7 m m K solution and only a slight relaxation was observed in 0 m m or 10.8 m m K solution. The initial transient relaxation was also inhibited by ouabain or low Na solution. 3 On an appropriate increase in the concentration of external K, noradrenaline‐induced contraction was transiently relaxed. Previous application of nitroglycerine potentiated this K‐induced relaxation. 4 Pretreatment of the muscle with methylene blue, an inhibitor of guanylate cyclase, inhibited both the initial transient and the sustained relaxations induced by nitroglycerine, but not the K‐induced transient relaxation. 5 It is suggested that the nitroglycerine‐induced initial transient relaxation, but not the sustained relaxation, may be due to a stimulation of an electrogenic Na pump. Both relaxation phases may be mediated by cyclic GMP.