Phosphorus-31 NMR studies of smooth muscle from guinea-pig taenia coli
Phosphorus-31 NMR spectra of superfused isometrically mounted guinea-pig taenia coli were obtained using a horizontal probe at 103.2 MHz. The spectra showed resonances for ATP, phosphocreatine (PCr), and a sugar phosphate resonance. The PCr/ATP ratio was between 1.5 and 2.0 consistent with chemical analysis of tissue extracts. The level of PCr, but not of ATP, decreases reversibly during contracti