Abstract
Attention has been called to the fact that cyanide in low concentration may reversibly inhibit the stimulating action of drugs on the smooth muscle of rabbit uteri and intestinal strips. 1 The usual procedure∗ was to produce a contracture by the addition of a certain amount of drug to the solution bathing the muscle in the Trendelenberg apparatus. After washing out the drug, a solution of neutralized, buffered M/2000 NaCN was added. Three to 5 minutes later the drug was again added in the original concentration. This almost invariably failed to produce any contracture whatever. Washing and again testing the tissue with the same concentration of drug produced a contracture similar to that first obtained.
Garry 2 noted that the response of smooth muscle to certain drugs may be abolished by oxygen lack, and that the normal tonus of the strips was decreased by small amounts of cyanide. We find that cyanide in concentrations as low as M/200,000 is capable of exerting an inhibiting action on the response of the strips to drugs. This suggests the possibility that the effect may depend upon a heavy metal catalytic system such as Warburg has demonstrated to be involved in biological oxidation. To test this possibility we have studied the effect of hydrogen sulphide and of carbon monoxide on this system. Hydrogen sulphide in a concentration of M/2,000, completely blocked the action of acetyl choline (2 × 10-6) on intestinal strips. Furthermore, it was found that mixtures of carbon monoxide and oxygen inhibited the action of adrenalin on uterus and of acetyl choline on the intestine in the dark in concentrations in which a mixture of nitrogen and oxygen of similar percentage composition had no such effect.
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