UDP-glucose effect on phrenic diaphragm preparation of the rat

The effects of uridine-5'-diphosphoglucose (UDPG) on the contractile response of the phrenic nerve-diaphragm preparation and on carbohydrate metabolism in the diaphragmatic muscle were studied in the rat. In the preparations obtained form rats, the contracturant action of UDPG, previously observed in guinea-pig preparations, was thus confirmed. This action was compared with those of uridine, UMP and UDP. Uridine alone was ineffective, while the higher concentration of both UMP and UDP induced a contracture comparable with that shown for the lower concentration of UDPG. This indicates that the action of UDPG is partially related at least to one phosphate-group into its molecular structure. In addition, several substrates and intermediates related to carbohydrate metabolism (glycogen, glucose, glucose-6-phosphate) were measured in the diaphragm, their concentrations proving unaffected by UDPG perfusion.