4.1. Historic observations
Several studies have shown that estrogens and related compounds may exert direct or indirect effects on mitochondrial function (Table 1). It has been reported that 17β-E2 inhibits mitochondrial F0F1-ATPase by binding to one of its subunits, the oligomycin sensitivity conferring protein [66,67]. A testable model for cytoprotective activity is that such inhibition impedes the reverse reactions of the ATPase during ischemia, using ATP to generate a membrane potential, thereby preserving cytosolic ATP arising from glycolysis. Other investigators have found that estradiol augments sequestration of cytosolic Ca2+ by mitochondria in the presence of glutamate which, given the diffusion limited kinetics of the Ca2+ uniporter, is prima facie evidence of mitochondrial stabilization [68]. Moderating Ca2+- induced permeability transition during excitoxicity, and in so doing maintaining OXPHOS, would clearly be beneficial. In another study, 17β-E2 has been shown to stabilize mitochondrial function and thereby protect neural cells against the pro-apoptotic action of mutant presenilin-1 [69]. Anti-apoptotic action may also involve receptor mediated transactivation such as the upregulation of Bcl-2, known to occur upon estradiol exposure.