Fig. 2.

Mitochondrial Grx1 content is decreased in both populations of heart mitochondria from elderly Fischer 344 rats. Mitochondrial Grx1 contents in the SSM and IFM from young adult and elderly F344 rat heart tissues were determined by interpolation of the band density of t-Bid-released Grx1, using a standard curve relating the densities of the bands of several different amounts of purified human Grx1 protein that were analyzed on the same gels in each respective case, as described previously [12]. The values are reported as ng Grx1 per mg of mitochondrial protein (mean±SEM, n=5) for (A) SSM and (B) IFM. Diminutions of Grx1 content were observed in the IFM and SSM from the elderly rats compared to the young adult rats. The diminution of mitochondrial Grx1 content in the elderly F344 rat hearts was corroborated using gold labeling of Grx1 antibodies based on electron microscopy analysis (C) and (D). Black arrows indicate Grx1 localization in the outer mitochondrial compartment (intermembrane space) of heart mitochondria from (C) young adult and (D) elderly F344 rats. Twenty-two gold particles were counted in the mitochondrial sample from young adult rats, compared to ten that were observed in the sample from the elderly rats.