Protein kinase C alterations in the fetal rat brain after global ischemia.

Marked changes in the intracellular localization of brain protein kinase C are evident after global ischemia generated by the restriction of the placental blood flow in the near-term rat embryo. A rapid (5 min) ischemia-dependent translocation of the enzyme from the cytosol to the particulate membrane fraction, which is completely reversible upon reperfusion, is observed. After 30 min of ischemia, substantial losses in protein kinase C activity and content as measured by [3H]phorbol dibutyrate binding are apparent. This is accompanied by a marked increase of a Ca2+-phosphatidylserine-independent kinase activity, already evident after 5 min of ischemia. By 15 or 30 min the total activity of the latter enzyme is equally distributed between the particulate and the cytosol fractions and is more than 3-fold higher in ischemic in comparison to naive animals. Activation and possible deregulation of protein kinase C are proposed to represent an initial step in the pathophysiology of brain ischemia.