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Effects of potassium channel toxins from Leiurus quinquestriatus hebraeus venom on responses to cromakalim in rabbit blood vessels
Author(s) -
Strong P.N.,
Weir Sheila W.,
Beech D.J.,
Hiestand P.,
Kocher H.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.tb14610.x
Subject(s) - charybdotoxin , cromakalim , apamin , venom , potassium channel , chemistry , potassium , potassium channel blocker , chromatography , biochemistry , endocrinology , biology , receptor , organic chemistry , agonist
1 The effects of fractionated Leiurus quinquestriatus hebraeus venom on cromakalim‐induced 86 Rb + efflux in rabbit aortic smooth muscle were examined. 2 Crude venom (0.1–30 μg ml −1 ) produced a concentration‐dependent decrease of 1 μ m cromakalim‐induced 86 Rb + response. The maximum blocking activity attainable was approximately 60%. 3 Fractionation of crude venom by gel permeation chromatography and subsequent chromatography on a cation ion‐exchange column, produced two fractions (X and XI), active in the 86 Rb + blocking assay. 4 Fraction XII contained charybdotoxin (∼85% pure). After a final high performance liquid chromatography (h.p.l.c.) purification step, the purified toxin failed to inhibit the cromakalim‐stimulated 86 Rb + efflux although it was a potent inhibitor of A23187‐induced K + flux in human erythrocytes and the large conductance calcium‐activated potassium channel in rabbit portal vein smooth muscle. 5 Subsequent purification of fraction X by h.p.l.c. yielded a minor peak which contained 86 Rb + blocking activity. This subfraction was also capable of inhibiting apamin‐sensitive, angiotensin II‐stimulated K + flux in guinea‐pig hepatocytes. 6 It is concluded that the potassium channel opened by cromakalim in rabbit aortic smooth muscle is not blocked by charybdotoxin but by another distinct toxin in the venom of Leiurus quinquestriatus hebraeus .