Localization of adenosine triphosphatase activity of the endothelia in chronic relapsing experimental allergic encephalomyelitis.

We used the method of ultracytochemical reaction for magnesium ion-dependent adenosine triphosphatase (Mg2+-ATPase) activity to study endothelial functions in various stages of chronic relapsing experimental allergic encephalomyelitis (EAE). In the endothelia of small vessels of the spinal cord of control guinea pigs, Mg2+-ATPase activity was cytochemically observed on the abluminal plasmalemma, and in pinocytotic vesicles and pits, but not on the luminal plasmalemma. The endothelia at the preclinical stage of EAE and in unaffected areas at various clinical stages, showed the same localization of Mg2+-ATPase activity as that in the control group. From the acute stage of active demyelination to the last stage of inactive lesions, Mg2+-ATPase activity in the endothelia of affected areas was localized on the luminal and abluminal surfaces of the plasmalemma, and in vesicles and pits. However, the intensity of the activity was lower than that in the control group. These findings suggest that, in chronic relapsing EAE, the endothelia of affected areas function differently from the endothelia of normal or unaffected areas.