Perinuclear mitochondrial clustering in hypoxia: role of microtubules and the dynein motor system. (A) Left image: The arrow points to the nucleus of a capillary endothelial cell in a perfused rat lung. Mitochondrial labeling is green. Right image: Arrows point to clustered mitochondria after 3 hours of hypoxia. Scale bar, 20 μm. (B) Rat PAECs stained with MitoTracker Red, Oregon Green paclitaxel (microtubules), and Hoechst 33342 (nuclei, blue) were cultured under normoxia or hypoxia for 3 hours. Yellow circle denotes perinuclear region. Scale bar, 30 μm. (C) Quantification of perinuclear mitochondrial distribution in normoxic (NORM) and hypoxic PAECs. (D) Distribution of mitochondria in concentric rings radiating from the nucleus outward in normoxic and hypoxic PAECs. (E) Mitochondrial distribution in normoxic and hypoxic PASMCs. (F) Impact of the microtubule-destabilizing agent nocodazole (Noc) on mitochondrial distribution in normoxic and hypoxic PAECs. (G) Impact of siRNA knockdown of the dynein heavy chain (siDYN) on mitochondrial distribution in normoxic and hypoxic PAECs. n = 6 different culture dishes with three to six cells analyzed per dish. *P < 0.05, different from normoxia.