Mechanism of inhibition of contraction by cadmium in guinea-pig taenia coli

Publisher Website
Google Scholar
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.