Spontaneous contractions and carbohydrate metabolism of isolated guinea-pig taenia coli

Abstract

When the muscle activity was recorded isometrically, the taenia generated spontaneous contractions having a minute rhythm with a period of 2-10 min in normal medium bubbled with 95% 02: 5% C02- During hypoxic conditions, bubbled with 95% N2: 5% CO2, contractile tension was markedly attenuated, but the rhythmicity remained constant, having the same period of spontaneous activity as that in aerobic conditions. When the taenia was exposed to glucose-removed and 2-deoxyglucose (10 mM)(2-DG)-containing medium in the aerobic conditions, spontaneous contractions were abolished. Potassium (40 mM)-induced tonic contraction was also inhibited by the glucose-removal and 2-DG-addition. When pyruvate (10 mM) was added to the glucose-removed and 2-DG-containing medium, potassium apparently caused full contraction, whereas spontaneous contractions still remained abolished. ATP content of the taenia was decreased by about 60% of the normal level when glucose was removed and 2-DG was added. Addition of pyruvate to the glucose-removed and 2-DG-containing medium kept the ATP content at the normal level. The results suggest that generation of rhythmicity of spontaneous contractions of the taenia coli is highly dependent on the glycolytic activity but not so much on the TCA-cycle activity of the smooth muscle cell.