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(Circulation. 2005;111:2022-2024.)
© 2005 American Heart Association, Inc.

Editorial

Tetrahydrobiopterin in Pulmonary Hypertension

Pulmonary Hypertension in Guanosine Triphosphate-Cyclohydrolase–Deficient Mice

Kirkwood A. Pritchard, Jr, PhD; Yang Shi, PhD; G. Ganesh Konduri

From the Department of Surgery, Division of Pediatric Surgery (K.A.P., Y.S.), Children’s Research Institute (K.A.P., Y.S., G.G.K.), Cardiovascular Center (K.A.P., Y.S., G.G.K.), Department of Pediatrics, Division of Neonatology (G.G.K.), Medical College of Wisconsin and Children’s Hospital of Wisconsin, Milwaukee, Wis.

Correspondence to Kirkwood A. Pritchard, Jr, PhD, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI 53226. E-mail kpritch@mcw.edu

Key Words: Editorials • hypertension, pulmonary • nitric oxide synthase • vasodilation

An extract of the first 250 words of the full text is provided, because this article has no abstract.

The regulation of pulmonary vascular tone is a complex process and represents a balance between constrictor and dilator influences. In pulmonary hypertension, whether caused by hypoxia or flow- and pressure-induced remodeling, the balance is tilted predominantly toward vasoconstriction. Despite decades of research, the initiating events in most patients with primary pulmonary hypertension remain unknown. The causes are probably diverse, and clinical recognition of the disease often occurs after the process is fairly advanced. On presentation, initiating events are obscured by the adaptations that occurred in the pulmonary circulation in response to the hypertension. Thus, the clinically evident disease may be quite distant from the initial cause(s) of pulmonary hypertension. Laboratory investigations of specific biochemical defects that can lead to pulmonary hypertension and vascular remodeling should help us understand these proximate causes. In this issue of Circulation, 2 independent studies^1,2 report that a defect in the synthesis of tetrahydrobiopterin (BH₄), a cofactor required for the synthesis of nitric oxide (^·NO) through the catalytic activity of NO synthase (NOS), results in pulmonary hypertension. The studies confirm that a defect in endothelial NOS (eNOS) function can be an initiating event leading to both pulmonary hypertension and pulmonary vascular remodeling. Their results are consistent with observations of impaired NOS activity and NOS-dependent vasodilation in both patients and animal models with pulmonary hypertension. Such studies provide proof of concept that a specific biochemical defect can cause eNOS uncoupling to remodel the pulmonary vasculature.

See pp 2086 and 2126

The mechanisms involved in . . . [Full Text of this Article]