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This Article Full Text Full Text (PDF) All Versions of this Article: 292/3/L678    most recent 00178.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Gao, Y. Articles by Usha Raj, J. Search for Related Content PubMed PubMed Citation Articles by Gao, Y. Articles by Usha Raj, J.

Role of Rho kinases in PKG-mediated relaxation of pulmonary arteries of fetal lambs exposed to chronic high altitude hypoxia

¹Division of Neonatology, Harbor-UCLA Medical Center, Geffen School of Medicine at University of California, and Los Angeles Biomedical Research Institute, Los Angeles, California; ²Key Laboratory of Molecular Cardiovascular Sciences, Peking University, Ministry of Education, Beijing, China; and ³Center for Perinatal Biology, Loma Linda University, School of Medicine, Loma Linda, California

Submitted 16 May 2006 ; accepted in final form 30 October 2006

An increase in Rho kinase (ROCK) activity is implicated in chronic hypoxia-induced pulmonary hypertension. In the present study, we determined the role of ROCKs in cGMP-dependent protein kinase (PKG)-mediated pulmonary vasodilation of fetal lambs exposed to chronic hypoxia. Fourth generation pulmonary arteries were isolated from near-term fetuses (140 days of gestation) delivered from ewes exposed to chronic high altitude hypoxia for 110 days and from control ewes. In vessels constricted to endothelin-1, 8-bromoguanosine-cGMP (8-Br-cGMP) caused a smaller relaxation in chronically hypoxic (CH) vessels compared with controls. Rp-8-Br-PET-cGMPS, a PKG inhibitor, attenuated relaxation to 8-Br-cGMP in control vessels to a greater extent than in CH vessels. Y-27632, a ROCK inhibitor, significantly potentiated 8-Br-cGMP-induced relaxation of CH vessels and had only a minor effect in control vessels. The expression of PKG was increased but was not accompanied with an increase in the activity of the enzyme in CH vessels. The expression of type II ROCK and activity of ROCKs were increased in CH vessels. The phosphorylation of threonine (Thr)696 and Thr850 of the regulatory subunit MYPT1 of myosin light chain phosphatase was inhibited by 8-Br-cGMP to a lesser extent in CH vessels than in controls. The difference was eliminated by Y-27632. These results suggest that chronic hypoxia in utero attenuates PKG-mediated relaxation in pulmonary arteries, partly due to inhibition of PKG activity and partly due to enhanced ROCK activity. Increased ROCK activity may inhibit PKG action through increased phosphorylation of MYPT1 at Thr696 and Thr850.

cGMP; myosin light chain phosphatases; vascular smooth muscle; cGMP-dependent protein kinase; Rho kinase

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