Figure 1.

Pulmonary arterial endothelial cells (PAECs) isolated from lambs with pulmonary hypertension exhibit increased mitochondrial fission. PAECs isolated from three pairs of Control and Shunt lambs and mitochondria labeled with MitoTracker (A) were analyzed to examine changes in mitochondrial network dynamics. Our data indicate that there are significant decreases in the mitochondrial aspect ratio (AR, B), the number of branches (C), and junctions (D) in PAEC isolated from Shunt lambs, indicative of increased mitochondrial fission. Western blot analysis shows that, although total Drp1 (E) levels are unchanged in Shunt PAEC, pS⁶¹⁶Drp1 (F) and the pS⁶¹⁶Drp1:total Drp1 ratio (G) are increased. Representative images are shown. β-Actin was used to normalize protein loading. Immunofluorescence microscopy shows increases in the localization of the mitochondrial fission protein Drp1 (H and I), and its activated phosphorylated form, pS⁶¹⁶Drp1, in the mitochondria of Shunt PAEC (J and K). Western blot analysis shows that the ratio of pS⁶¹⁶Drp1 to total Drp1 increases in peripheral lung tissue prepared from 4-week-old Shunt, compared with Control lambs (L). Representative images are shown. β-Actin was used to normalize protein loading. The scale bar represents 10 μm. Data are mean ± SE. ∗p < 0.05 versus Control PAEC or Control lung.