title: Mechanism of inhibition of contraction by cadmium in guinea-pig taenia coli.
abstract: Further evidence about the mechanism of the inhibition of contractions caused by cadmium ions (Cd2+) in guinea-pig taenia coli has been sought. Cd2+ at a concentration of 0.5 mM completely inhibited the high-K (40 mM)-induced contraction within 3-5 min. Cd2+ did not shift the Ca2+-induced concentration-response curve to the right in Ca2+-free K+ depolarized muscle, although it reduced the Ca2+ response size. The K+-induced increase in tissue calcium content and 45Ca uptake determined by the lanthanum method was significantly reduced in the presence of Cd2+ (0.5 mM) and the contractions of the glycerolated taenia coli were inhibited with increasing Cd2+ (0.001-0.5 mM). Muscle strips, incubated in a medium containing 0.5 mM Cd2+, accumulated greater amounts of cadmium than within the extracellular space. It is suggested that the inhibitory action on tension produced by Cd2+ in taenia coli may result from the interference of calcium permeability at the cell membrane. There is the possibility that Cd2+ acts on the contractile system of the muscle.
mesh_terms: D000818:Animals; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes; D003106:Colon / Q000187:drug effects; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology
chemical_list: D002132:Calcium Radioisotopes; D002104:Cadmium; D011188:Potassium; D002118:Calcium