Reduced Na++K+-ATPase activity in peripheral nerve of streptozotocin-diabetic rats: a role for protein kinase C?

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Abstract
Summary Six weeks after induction of diabetes, the rate of ouabain-sensitive 86Rb+ accumulation, a parameter which reflects Na++K+-ATPase pumping activity, was significantly reduced in endoneurial preparations of sciatic nerve from untreated diabetic rats compared with that in control rats (Trial 1, 0.19±0.09 versus 0.48±0.13 pmol/min per mg wet weight of tissue, pp86Rb+ uptake was not observed in nerves from diabetic rats maintained on sorbinil (an aldose reductase inhibitor) or myo-inositol diets. Protein kinase C activity was demonstrated in the soluble fraction of a sciatic nerve homogenate by assaying for lipid-activated, Ca+-dependent phosphorylation of calf thymus histone. No significant difference in the time course of kinase C activity was observed between cytosol fractions of nerve homogenates from control and diabetic rats (control, 6.22±0.97 pmol 32P incorporated/mg cytosol protein in 50 min; diabetic, 5.32±0.71). Three low molecular weight neural proteins (each with Mr<29,000) were identified as substrates for protein kinase C.