The long-term goal of this project is to investigate the fundamental interactions among oxygen, nitric oxide (NO) and hemoglobin (Hb) at the level of the microcirculation, using combined experimental and theoretical approaches. Nitric oxide can affect two key aspects of oxygen supply and demand (1) through its action as a vascular smooth muscle relaxant and (2) through its action as an inhibitor of cytochrome c oxidase. The ability of enzymatic sources of NO to account for experimental values of [NO] in and around microvessels will be assessed by analyzing immunohistochemical localization of NOS isoforms, applying specific inhibitors of NOS to experimental animals, measuring [NO] using microelectrodes and a new fluorescence technique, and comparing the results with predictions of specialized biochemical models of NO production, where specific NOS isoforms can be removed from the calculation (in silico knockout). Experiments will be carried out on the spinotrapezius muscle of normotensive (WKY) and spontaneously hypertensive rats (SHR). The balance between oxygen supply and demand will be altered by changing one or both variables. Oxygen supply will be altered by changing systemic hematocrit (normovolemic hemodilution or hemoconcentration) and oxygen demand will be increased by electrically stimulating the spinotrapezius muscle. Plasma and tissue PO2 will be measured using phosphorescence quenching microscopy, hemoglobin oxygen saturation in microvessels will be measured microspectrophotometrically, microvascular geometry and hemodynamic parameters will be measured using video imaging techniques, oxygen consumption will be measured by the stop-flow technique, and [NO] will be measured as described above. The microvascular responses to reduced oxygen supply to demand ratio will be related to changes in [NO]. The degree to which NO changes in response to the decreased oxygen supply/oxygen demand will be compared between the WKY and SHR, and the experimental results will be compared with predictions of the computational model that employs parameters specific to the WKY and SHR subjects. We will also theoretically analyze the pathways that lead to NO synthesis in the microvasculature and their contributions to regulating oxygen delivery and demand. An integrative model that will combine the biochemical pathway analysis of NO production, the biotransport of NO, and the distribution of oxygen will be developed. The experimentally determined vascular and tissue PO2 and [NO] will be thoroughly compared with the predictions of the biophysically and biochemically detailed computational models. Thus, the project will include state-of-the-art combined experimental and computational studies that should lead to a better quantitative understanding of NO release and dynamics and the interplay between NO release and oxygen delivery, two cornerstones of vascular biology. Public Health Relevance: The long-term objective of the project is to provide a physiological basis for understanding the mechanisms of nitric oxide (NO) production, as well as to gain a better knowledge of the general mechanisms of NO transport in the vasculature. Moreover, the proposed studies will provide information that will lead to better treatment of various cardiovascular diseases through utilizing NO-induced vasodilation and oxygen delivery pathways.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL018292-33
Application #
8073178
Study Section
Special Emphasis Panel (ZRG1-HM-D (02))
Program Officer
Schwartz, Lisa
Project Start
1994-01-01
Project End
2014-05-31
Budget Start
2011-06-01
Budget End
2014-05-31
Support Year
33
Fiscal Year
2011
Total Cost
$523,419
Indirect Cost
Name
Virginia Commonwealth University
Department
Physiology
Type
Schools of Medicine
DUNS #
105300446
City
Richmond
State
VA
Country
United States
Zip Code
23298
Nugent, William H; Song, Bjorn K; Pittman, Roland N et al. (2016) Simultaneous sampling of tissue oxygenation and oxygen consumption in skeletal muscle. Microvasc Res 105:15-22
Golub, Aleksander S; Pittman, Roland N (2014) A paradigm shift for local blood flow regulation. J Appl Physiol (1985) 116:703-5
Golub, Aleksander S; Song, Bjorn K; Pittman, Roland N (2014) Muscle contraction increases interstitial nitric oxide as predicted by a new model of local blood flow regulation. J Physiol 592:1225-35
Song, Bjorn Kyungsuck; Nugent, William H; Moon-Massat, Paula F et al. (2014) Effects of a hemoglobin-based oxygen carrier (HBOC-201) and derivatives with altered oxygen affinity and viscosity on systemic and microcirculatory variables in a top-load rat model. Microvasc Res 95:124-30
Golub, Aleksander S; Pittman, Roland N (2013) Bang-bang model for regulation of local blood flow. Microcirculation 20:455-83
Pittman, Roland N (2013) Oxygen transport in the microcirculation and its regulation. Microcirculation 20:117-37
Song, Bjorn Kyungsuck; Nugent, William H; Moon-Massat, Paula F et al. (2013) Effects of top-loading a zero-link bovine hemoglobin, OxyVita, on systemic and microcirculatory variables. Mil Med 178:570-7
Golub, Aleksander S; Pittman, Roland N (2012) Oxygen dependence of respiration in rat spinotrapezius muscle in situ. Am J Physiol Heart Circ Physiol 303:H47-56
Liu, Gang; Mac Gabhann, Feilim; Popel, Aleksander S (2012) Effects of fiber type and size on the heterogeneity of oxygen distribution in exercising skeletal muscle. PLoS One 7:e44375
Golub, Aleksander S; Tevald, Michael A; Pittman, Roland N (2011) Phosphorescence quenching microrespirometry of skeletal muscle in situ. Am J Physiol Heart Circ Physiol 300:H135-43

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