Phosphorylation of myelin basic proteins: an age-dependent process affected by divalent cations and Co-Dergocrine...

Separation of rat cortical or hippocampal myelin preparations after in vitro phosphorylation on sodium dodecyl sulfate slab gel electrophoresis revealed several phosphorylated proteins with molecular weights between 12,000 and 25,000. The major phosphate acceptors seemed to be two basic proteins. This in vitro phosphorylation of myelin uses endogenous phosphokinase activity and was not influenced by biologically relevant concentrations of cyclic AMP or cyclic GMP. However, phosphorylation was stimulated by addition of Ca2+ and completely inhibited by omission of Mg2+ from the incubation medium. In vitro phosphorylation of CNS myelin proved to be age dependent: increased phosphate incorporation into CNS myelin basic proteins was observed up to the age of about 12 weeks. A steady decline in phosphate incorporation occurred thereafter leaving little in vitro phosphorylating capacity at 80 weeks of age or more. Old animals (80 weeks), when treated with Co-Dergocrine, showed improved in vitro phosphorylating capacity of myelin preparations approaching that found in young control animals.