Are mitochondria involved in contractures of Vorticella?

1. Negatively charged derivatives of compounds inducing Vorticella contractures are inactive. It seems, therefore, that the action of compounds inducing contractures is intracellular. 2. Most compounds are not absolutely selective for reticular vs. mitochondrial involvement. After correlating the effect of many agents, however, we consider a cyclic mitochondrial uptake-release mechanism likely. 3. In the absence of extracellular calcium we still obtained about half as many contractures, in some cases up to 400/Vorticella per hr. With many compounds, therefore, when less contractures are observed, it cannot be due to lack of intracellular calcium. 4. In addition, we consider a hypothesis in which the external calcium acts to amplify a "signal" induced by the stimulating agents. This signal in turn activates the mitochondrial uptake-release cycle. 5. The metabolism of the cell definitely influences the pharmacodynamic coupling.