Asymmetric dimethylarginine (ADMA) decreases endothelial tube formation (A, B) in human pulmonary artery endothelial cells (HPAECs). HPAECs were treated with 18β-GA, ADMA, L-257, or rotigaptide or were overexpressing AdDDAHI, AdCx43, or AdGFP, as indicated. B shows representative images of tube formation in HPAECs treated, as indicated. Scale bar = 100 μm. One asterisk: ; two asterisks: , comparison with control; one Delta: ; two Deltas: ; three Deltas: , comparisons between ADMA + treatment and ADMA groups. .