Ultracytochemical localization of Ca2+-ATPase activity in reactive astrocytes.

Ca2+-ATPase activity on the astrocyte plasma membrane was investigated ultracytochemically, using the lead salt technique. Normal astrocytes showed a weak cytochemical reaction for Ca2+-ATPase activity, deposits of the reaction product being small. At 7 and 15 days after cold lesioning, reactive astrocytes apparently in the process of repair of the edematous lesion were observed; these demonstrated an intense cytochemical reaction for Ca2+-ATPase activity in their plasma membranes facing the extracellular fluid, with reaction product accumulation. At 2 months, the lesion had progressed to glial scars containing sporadic microcysts. The reactive astrocytes surrounding the microcysts demonstrated a moderate cytochemical reaction for Ca2+-ATPase activity in their free plasma membranes, whereas those arranged in a cell-to-cell pattern showed little reaction product in their plasma membranes. In conclusion, a more intense cytochemical reaction was always observed in the free plasma membrane of reactive astrocytes.