Changes in Cytochrome P450-Dependent Activities and Isozyme Levels Following Cerebral Ischemia
Mullendore, Sean T.
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Cerebral ischemia has been shown to cause a number of metabolic changes including an accumulation of free fatty acids (Bazan, 1970; Kogure and Nakano, 1992). In extrahepatic tissues such as kidney and cornea, cytochrome P450 has been implicated in the production of biologically active compounds from the metabolism of free fatty acids such as arachidonate (McGiff, 1991; Davis et al., 1992). In the present study, cytochrome P450 enzyme activity in rat brain was measured through the analysis of P450-dependent metabolism of testosterone following 10 minute periods of global cerebral ischemia. Western Blotting was also performed using polyclonal antibodies specific for purified hepatic microsomal P450 2E1 and P450 1A1 to examine levels of these isozymes. Preliminary fin~gs suggested that there is differential regulation of cytochrome P450-dependent testosterone hydroxylation in brain microsomes and mitochondria following the induction of stroke. In these experiments, levels of 16 𝛽 -, 2α-, and possibly 2𝛽-hydroxytestosterone increased in rat brain microsomes following stroke treatment; whereas levels of 6𝛽-hydroxytestosterone decreased. The levels of 16α-hydroxytestosterone were unchanged. Western Blot analysis of rat brain microsomes revealed a protein similar in molecular weight and antigenic specificity to hepatic P450 2E1. A smaller weight protein which reacted with antibodies to P450 2E1 was found in all stroke-treated animals and one control animal. Western Blot analysis of rat brain mitochondria revealed a protein similar in molecular weight and antigenic specificity to hepatic P450 1A1, suggesting elevated levels of P450 1A1 in stroke-treated animals.