Dinitrofluorobenzene-induced rigor in ileal longitudinal smooth muscle of the guinea-pig

1. The administration of 2,4-dinitrofluorobenzene (DFB) (0.1-1 mM) to the ileal longitudinal muscle produced contractions within seconds of its administration. 2. A component of the first 2 min duration of the phasic phase of 1 or 0.5 mM DFB contraction and the first phase of 0.35 or 0.1 mM DFB contraction was inhibited by Ca2+ antagonists, 1 x 10(-6) M D-600. 3. The DFB contraction resistant to D-600 began to develop when the tissue ATP concentration rapidly reduced. 4. The DFB contraction in ileum consists of two components; an initial fast contraction which is sensitive to Ca2+ antagonists, and a late contraction referred to as a rigor which is resistant to it.