The effect of adrenaline on the adenosine otriphosphate and creatine phosphate content of intestinal smooth muscle.

1. The smooth muscle of guinea-pig taenia coli was used to investigate the relation between metabolic and physiological effects of adrenaline. Electrical and mechanical activity was recorded with the sucrose gap technique and, in parallel experiments, the concentration of energy-rich phosphate compounds, adenosinetriphosphate and creatine phosphate, (ATP and CP) in the tissue was determined.2. Adrenaline (in concentrations from 2 x 10(-9) g/ml. to 5 x 10(-8) g/ml.) increased the tissue content of energy-rich phosphate compounds. This effect was coincident with the physiological, inhibitory effect on electrical and mechanical activity.3. After anaerobic exposure of the tissue to substrate-free medium, the biochemical and the physiological effects of adrenaline were both abolished; both recovered after readmission of oxygen and/or substrate.4. In muscles depleted of glycogen in substrate-free medium, either by anoxia or by high temperature, adrenaline produced its stabilizing effect on the cell membrane and the increase in ATP and CP content when beta-hydroxybutyrate was the substrate, i.e. in the complete absence of carbohydrate from the medium and from the tissue.5. When adrenaline was applied simultaneously with the readmission of substrate, the ATP and CP content of pieces treated with adrenaline was greater than of control pieces, though the tension of both was zero. This indicates that the effect was not secondary to the muscle relaxation but was the result of increased ATP synthesis.6. The physiological and biochemical effects of adrenaline were both abolished by the same concentration of imidazole (0.05 M).7. Low concentrations of ATP (1 x 10(6)-5 x 10(-6)M)-like adrenaline-inhibited electrical and mechanical activity of the taenia. This effect was also abolished by imidazole.