Neuronal subclass-selective loss of pyruvate dehydrogenase immunoreactivity following canine cardiac arrest and resuscitation

Chronic impairment of aerobic energy metabolism accompanies global cerebral ischemia and reperfusion and likely contributes to delayed neuronal cell d eath. Reperfusion-dependent inhibition of pyruvate dehydrogenase complex (P DHC) enzyme activity has been described and proposed to be at least partial ly responsible for this metabolic abnormality. This study tested the hypoth esis that global cerebral ischemia and reperfusion results in the loss of p yruvate dehydrogenase immunoreactivity and that such loss is associated wit h selective neuronal vulnerability to transient ischemia. Following 10 min canine cardiac arrest, resuscitation, and 2 or 24 h of restoration of spont aneous circulation, brains were either perfusion fixed for immunohistochemi cal analyses or biopsy samples were removed for Western immunoblot analyses of PDHC immunoreactivity, A significant decrease in immunoreactivity was o bserved in frontal cortex homogenates from both 2 and 24 h reperfused anima ls compared to samples from nonischemic control animals. These results were supported by confocal microscopic immunohistochemical determinations of py ruvate dehydrogenase immunoreactivity in the neuronal cell bodies located w ithin different layers of the frontal cortex. Loss of immunoreactivity was greatest for pyramidal neurons located in layer V compared to neurons in la yers IIIc/IV, which correlates with a greater vulnerability of layer V neur ons to delayed death caused by transient global cerebral ischemia. (C) 2000 Academic Press.