Vasomotor signaling of endothelin-1 in isolated porcine retinal arterioles : a dissertation /
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[College Station, Tex.] :
[Texas A&M University System Health Science Center],
[2014]
|
| Subjects: |
| Abstract: | ABSTRACT: Increased ocular production or sensitivity to the vasoconstrictor peptide ET-1 has been suggested to contribute to retinal pathologies such as diabetic retinopathy, glaucoma and retinal vein occlusion. However, the underlying machanism of ET-1-induced vasoconstriction is incompletely understood. This study addressed the contributions of extracellular calcium (Ca²⁺), L-type voltage-operated calcium channels (L-VOCCs), Rho kinase (ROCK), and protein kinase C (PKC) to ET-1-induced constriction of porcine retinal arterioles, all of which have been commonly implicated in vascular smooth muscle contraction. ET-1 is synthesized from its precursor big ET-1 via endothelin converting enzyme-1 (ECE-1), present in the vascular wall. However, the relative contributions of endothelial and smooth muscle ECE-1 to this process are unknown. Although retinal arteriolar constriction is primarily mediated release of vasodilator substances from endothelium has been reported and this process could potentially mitigate ET-1-induced vasoconstrictor responses. However, it remains unclear whether this speculation is true for the retinal vasculature. To address these questions without confounding influences from neurohumoral and hemodynamic factors, porcine retinal arterioles were isolated for vasomotor study in vitro. Molecular and immunohistochemical tools were employed to assess expression and localization of signaling proteins. We found that extracellular Ca²⁺ entry via L-VOCCs and basal smooth muscle ROCK activity play important roles in the maintenance of basal tone of retinal arterioles. ROCK1 and ROCK2 isoforms are expressed in both endothelial and smooth muscle cells of retinal arterioles. ET-1-induced constriction is mediated by extracellular Ca²⁺ entry independent of L-VOCCs and by smooth muscle ROCK activation without PKC involvement. However, direct PKC activation causes vasoconstriction via L-VOCC activation and smooth muscle ROCK signaling, and endothelium-dependent vasodilation in the presence of L-VOC blockade. ECE-1 in endothelial and smooth muscle cells contribute equally to the conversion of big ET-1 to vasoactive ET-1. However, there is no vasomotor role for endothelial ET[subscript B] receptors, and endothelial production of vasodilator nitric oxide by flow (shear stress) does not mitigate vasoconstriction to ET-1. In conclusion, extracellular Ca²⁺ and smooth muscle ROCK activity mediate vasoconstrictor ET-1 signaling in retinal arterioles, and endothelial release of vasodilator substances does not reduce this constrictor response. |
|---|---|
| Item Description: | Vita. "Major Subject: Biomedical Science". "Submitted to The Office of Research and Graduate Studies of The Texas A&M University System Health Science Center in partial fulfillment of the requirements for the degree of Doctor of Philosophy May 2014." Approved as to style and content by: Lih Kuo, Brett Mitchell, Travis W. Hein, Robert H. Rosa, Jr., Harris Granger. Title on approval page (Smooth muscle ... ) differs from title page and abstract. |
| Physical Description: | ix, 123 leaves : illustrations (some color) ; 28 cm. |
| Bibliography: | Includes bibliographical references (leaves 27-45, 69-76, 99-105,116-122). |