Department of Cell Biology and Physiology

Faculty

Benjimen R. Walker, Ph.D.

Research Interest

Our laboratory studies the physiology of the cardiovascular system. Of special interest are the effects of impaired oxygenation (hypoxia) on vascular regulation both in the systemic and pulmonary circulations. Within the systemic vasculature, prolonged hypoxia causes diminished reactivity to vasoconstrictor stimuli that persists upon restoration of normal oxygenation. Our recent work suggests that this attenuated reactivity may be the result of enhanced release of the vasodilators carbon monoxide and epoxyeicosatrienoic acids (EETs) from the vascular endothelium. Current experiments are examining the factors regulating this enhanced release and the mechanisms by which these factors affect vascular smooth muscle function in this setting. Another result of chronic hypoxia is the development of pulmonary hypertension. We are examining the interactions between the endothelial factors nitric oxide and endothelin during the development of hypertension in the lung. A number of approaches are employed in our laboratory to study vasoreactivity, including the study of conscious, chronically instrumented animals, isolated organs and pressurized resistance vessels. We also are able to perform intracellular calcium and electrophysiological measurements on resistance vessels as well as use molecular biological techniques to assess gene expression within the vasculature. This integrated approach allows us to investigate how altered vascular gene expression affects the physiological responses of the whole animal as well as to determine the cellular mechanisms that may be altered by stimuli such as hypoxia.

Education, Honors and Professional Experience

B.S., Biology, Southern Colorado State College
M.S., Zoology and Physiology, University of Wyoming
Ph.D., Physiology, State University of New York at Buffalo School of Medicine
Postdoctoral Fellow, University of Colorado Health Sciences Center
Assistant Professor of Physiology, Tulane University School of Medicine
Associate Professor of Physiology, Tulane University School of Medicine
Assistant Professor of Physiology, University of New Mexico School of Medicine
Associate Professor of Physiology, UNMSOM
Professor of Cell Biology and Physiology, UNMSOM, 1995 – present
Established Investigator of the American Heart Association
UNMSOM Faculty Teaching Excellence Award, 1998-99, 2000-01
Fellow, American Heart Association
Fellow, Cardiovascular Section of American Physiological Society

Current Lab Personnel

Minerva Murphy, B.S., Senior Research Technician
Karen Sweazea, Ph.D., Postdoctoral Fellow
Michael Paffett, Graduate Student
Melissa Riddle, Graduate Student

Selected Recent Publications (click on reference for PubMed abstract)

Naik, J.S. and B.R. Walker.  Role of vascular heme oxygenase in reduced myogenic reactivity following chronic hypoxia. 
Microcirculation  13: 81-88, 2006.

Jernigan, N.L., B.R.S. Broughton, B.R. Walker and T.C. Resta.  Impaired NO-dependent inhibition of store- and receptor-operated calcium entry in pulmonary vascular smooth muscle following chronic hypoxia. 
Am. J. Physiol.  290: L517-L525, 2006.

Allahdadi, K., B.R. Walker and N.L. Kanagy.  Augmented endothelin vasoconstriction in intermittent hypoxia-induced hypertension. 
Hypertension 45: 705-709, 2005.

Naik, J.S., S. Earley, T.C. Resta and B.R. Walker.  Pressure-induced smooth muscle depolarization in pulmonary arteries from control and chronically hypoxic rats does not cause myogenic vasoconstriction.  J.
Appl. Physiol.  98: 1119-1124, 2005.

Earley, S., T.C. Resta and B.R. Walker.  Disruption of smooth muscle gap junctions attenuates myogenic vasoconstriction of mesenteric resistance arteries. 
Am. J. Physiol.: Heart and Circ. Physiol.  287: H2677-H2686, 2004.

Jernigan, N.L., B.R. Walker and T.C. Resta.  Chronic hypoxia augments protein kinase G-mediated Ca2+ desensitization in pulmonary vascular smooth muscle through inhibition of RhoA/Rho kinase signaling. 
Am. J. Physiol.: Lung Cell. Mol. Physiol.  287: L1220-L1229, 2004.

Chicoine, L.G., E. Tzeng, R. Bryan, S. Saenz, M.L. Paffett, J. Jones, C.R. Lyons, T.C. Resta, L.D. Nelin and B.R. Walker.  Intratracheal adenoviral iNOS transduction decreases pulmonary vasoconstrictor responses in rats. 
J. Appl. Physiol.  97: 1814-1822, 2004.

Jernigan, N.L., B.R. Walker and T.C. Resta.  Endothelium-derived reactive oxygen species and endothelin-1 attenuate NO-dependent pulmonary vasodilation following chronic hypoxia.  
Am. J. Physiol.: Lung Cell. Mol. Physiol.  287: L801-L808, 2004.

Jernigan, N.L., T.C. Resta and B.R. Walker.  Contribution of oxygen radicals to altered NO-dependent pulmonary vasodilation in acute and chronic hypoxia. 
Am. J. Physiol.: Lung, Cell. Mol Physiol.  286: L947-L955, 2004.

Jernigan, N.L., B.R. Walker and T.C. Resta.  Pulmonary PKG-1 is upregulated following chronic hypoxia.
Am. J. Physiol.: Lung Cell. Mol. Physiol. 285: L634-L642, 2003.  '

Kanagy, N.L., M. Perrine, D. Cheung and B.R. Walker.  Erythropoietin administration in vivo increases vascular nitric oxide synthase expression. 
 J. Cardiovasc. Pharmacol.  42: 527-533, 2003.'

Naik, J.S. and B.R. Walker.  Endogenous CO-mediated vasodilation involves vascular smooth muscle cell hyperpolarization.
Am. J. Physiol.: Heart and Circ. Physiol.285: H220-H228, 2003.

Earley, S., A. Pastuszyn and B.R. Walker. Cytochrome P450 epoxygenase products contribute to attenuated vasoconstrictor responsiveness following chronic hypoxia.  Am. J. Physiol.: Heart and Circ. Physiol. 285: H127-H136, 2003.

Earley, S. and B.R. Walker.'  Increased nitric oxide production following chronic hypoxia contributes to attenuated systemic vasoconstriction.
Am. J. Physiol.: Heart and Circ. Physiol. 284: H1655-H1661, 2003.'

Naik, J.S., T.L. O’Donaughy and B.R. Walker. Endogenous carbon monoxide is an endothelial-derived vasodilatory factor in the mesenteric circulation.
Am. J. Physiol.: Heart and Circ. Physiol. 284: H838-H845, 2003.

Earley, S. and B.R. Walker.'  Endothelium-dependent blunting of myogenic responsiveness after chronic hypoxia.
Am. J. Physiol.: Heart and Circ. Physiol. 283: H2202-H2209, 2002.'

O’Donaughy, T.L., T.C. Resta and B.R. Walker. Laboratory demonstration of baroreflex control of heart rate in conscious rats.
Adv. Physiol. Educ. 26: 309-316, 2002.

Resta, T.C., B.R. Walker, M.R. Eichinger and M.P. Doyle. Rate of NO scavenging alters effects of recombinant hemoglobin solutions on pulmonary vasoreactivity.
J. Appl. Physiol. 93: 1327-1336, 2002.

Chicoine, L.G., J.W. Avitia, C. Deen, S. Earley, L.D. Nelin and B.R. Walker. Developmental differences in pulmonary eNOS expression in response to chronic hypoxia in the rat.
 J. Appl. Physiol. 93: 311-318, 2002.

Earley, S., J.S. Naik and B.R. Walker. 48 hour hypoxic exposure results in endothelium-dependent systemic vascular smooth muscle cell hyperpolarization.
Am. J. Physiol.: Regulatory, Integrative and Comparative Physiol.  283: R79-R85, 2002.

Earley, S., L.G. Chicoine, L.D. Nelin and B.R. Walker. Hypoxia-induced pulmonary endothelin-1 expression is unaltered by nitric oxide.
 J. Appl. Physiol. 92: 1152-1158, 2002.

Gonzales, R.J. and B.R. Walker. Role of CO in attenuated vasoconstrictor reactivity in mesenteric resistance arteries following chronic hypoxia. 
Am. J. Physiol. Heart Circ. Physiol.  282: H30-H37, 2002.'

Naik, J.S. and B.R. Walker.'  Homogeneous segmental profile of carbon monoxide-mediated pulmonary vasodilation in rats. 
 Am. J. Physiol. Lung Cell. Mol. Physiol.  281: L1436-L1443, 2001.'

Jernigan, N.L., T.L. O’Donaughy and B.R. Walker.  Correlation of HO-1 expression with onset and reversal of hypoxia-induced vasoconstrictor hyporeactivity.
Am. J. Physiol. Heart Circ. Physiol  281: H298-H307, 2001.

Malvin, G.M. and B.R. Walker.'  Sites and ionic mechanisms of hypoxic vasoconstriction in frog skin. 
Am. J. Physiol.: Regulatory, Integrative and Comparative Physiol.  280: R1308-R1314, 2001.'

Gonzales, R.J., B.R. Walker and N.L. Kanagy. 17b-estradiol increases nitric oxide-dependent dilation in rat pulmonary arteries and thoracic aorta.
Am. J. Physiol. Lung Cell. Mol. Physiol.

Kanagy, N.L., B.R. Walker and L.D. Nelin. Role of endothelin in intermittent hypoxia-induced hypertension. Hypertension 37: 511-515, 2001.

Resta, T.C., N.L. Kanagy, and B.R. Walker. Estradiol-induced attenuation of pulmonary hypertension is not associated with altered eNOS expression.
Am. J. Physiol. Lung Cell. Mol. Physiol. 280:L88-L97, 2001.

O’Donaughy, T.L. and B.R. Walker. Renal vasodilatory influence of endogenous carbon monoxide in chronically hypoxic rats.
Am. J. Physiol. Heart Circ. Physiol. 279: H2908-H2915, 2000.

Walker, B.R., T.C. Resta, and L.D. Nelin. Nitric oxide-dependent pulmonary vasodilation in polycythemic rats.
Am. J. Physiol. Heart Circ. Physiol. 279:H2382-H2389, 2000.