Premium
MECHANISM OF CADMIUM‐INDUCED CONTRACTION IN ILEAL LONGITUDINAL MUSCLE OF GUINEA‐PIG
Author(s) -
ASAI FUMITOSHI,
NISHIMURA MASAKAZU,
SATOH EIKI,
URAKAWA NORIMOTO
Publication year - 1982
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.1476-5381.1982.tb09174.x
Subject(s) - guinea pig , contraction (grammar) , muscle contraction , new guinea , mechanism (biology) , cadmium , anatomy , endocrinology , chemistry , medicine , biology , philosophy , history , ethnology , epistemology , organic chemistry
1 The mechanism of cadmium (Cd 2+ )‐induced contraction was studied in isolated ileal longitudinal muscle of guinea‐pig. 2 CdCl 2 (1 × 10 −8 to 1 × 10 −4 m ) caused a transient contraction which subsided within approximately 6 min of application. The contraction was reproducible and dependent on the concentration. The dose‐response curve was bell‐shaped. A maximal response was observed at concentrations of 5 × 10 −6 to 1 × 10 −5 m . 3 The contractile effect was inhibited to some degree at 20°C or by tetrodotoxin (0.1 μg/ml), hyoscine (0.1 μg/ml) or hexamethonium (10 μg/ml), but completely inhibited by Ca 2+ ‐removal from the medium. 4 Cd 2+ increased the output of [ 14 C]‐acetylcholine biosynthesized from [ 14 C]‐choline by the preparation depending on the concentration. The increase terminated within the first 6 min and was reduced by tetrodotoxin (0.1 μg/ml) or by removal of Ca 2+ from the medium. 5 Both the contractile and transmitter releasing effects of Cd 2+ were dependent on the concentration of external Ca 2+ . Strontium ions were able to replace Ca 2+ for Cd 2+ ‐induced transmitter release. 6 It is suggested that Cd 2+ contracts ileal longitudinal muscle through a release of cholinergic transmitter from the parasympathetic nerve terminals, which is dependent on external Ca 2+ . It also has a smaller hyoscine‐resistant contractile effect, presumably due to a direct action on smooth muscle cells.