[Characterization of the effect of bradykinin on the smooth muscle with special reference to its latency]

The biological activity of bradykinin on the isolated guinea-pig ileum is evident after a defined period of time - its latency. The latency of a bradykinin induced contraction is not caused by the strong protonization of the polypeptide. Analogues with the same or diminished basicity have a shorter latency than bradykinin. The latency is increased at high hydrogen concentration in comparison with the physiological pH-value. But this phenomenon is also observed at angiotensin, eledoisin, acetylcholine, histamine and barium chloride. The latency is dependent upon the temperature. Exogenous calcium ions are without demonstrable influence on the bradykinin induced latency. The membrane potential is not changed during the latency. The results are discussed in connection with the drug-receptor interactions.