[Relationship between the insulin-stimulated disappearance of inorganic phosphate in vitro and the effect of insulin on creatine accumulation in rat skeletal muscle plasma membranes].

Total content of creatine was increased in unfractionated membrane fractions within 5-30 min after incubation at 30 degrees of the repeatedly washed and suspended in 0.25 M sucrose plasmatic membranes, isolated from rat skeletal muscle, using a medium containing tris-HCl buffer, rH 7.5, AMP and ADP, Mg2+, creatine, inorganic phosphate, NaF, NAD or NAD-dependent system of lactate oxidation (NAD, lactate, cytochrome c and O2) in presence of insulin (4 mg/ml). This increase in total content of creatine, stimulated by insulin, was accompanied by rapid diappearance of inorganic phosphate, which was especially distinct within 1 min of inculation at 30 degrees. Nonactive derivative of insulin (desoctapeptide insulin) did not affect the accumulation of creatine. The effect of inculin on accumulation of creatine was abolished by means of addition of EGTA into the medium or by excluding of Mg2+-AMP and of inorganic phosphate from the medium. The phenomenon observed might be related to synthesis of ATP, required for the physiological activity of insulin during transport of creatine across the biomembranes.