Effect of dietary supplementation with a phosphatidyl-inositol metabolite, cerophoshorylinositol, on Na+/K+ATPase activity and body weight i9n normal rats

Among the functions related to the inositol-containing phospholipids in the mammalian cells there is the activation of the Na+/K+ ATPase. A reduction of the activity of this enzyme is implicated in the reduced motor nerve conduction velocity observed in diabetic rats, in which concentration of free inositol in the peripheral nerve is lower than in normal rats. Even erythrocytes from diabetics have fewer sodium pumps than do erythrocytes from age-matched controls. Feeding normal, weaning rats glycerophosphorylinositol (GPI), a metabolite of myo-inositol, we investigated the connections among inositol availability, sodium pump activity, and development. Unexpectedly, GPI supplementation determined a reduction in the Na+/K+ ATPase activity and a decrease in the phosphatidylinositol content in the erythrocyte membranes, without altering the phosphatidylinositol fatty acid composition. Apart from all considerations about the mechanism of action of GPI, these data clearly state the relationship between sodium pump activity and phosphatidylinositol levels.