|
Wake Forest Physics…
Nationally recognized for teaching excellence;
internationally respected for research advances;
a focused emphasis on interdisciplinary study and close student-faculty collaboration; committed
to a diverse and inclusive environment.
|
WFU Physics Colloquium
TITLE:
Ph. D. Thesis presentation:
Nitric oxide bioavailability regulation by hemoglobin
SPEAKER:
Ivan A. Azarov,
Department of Physics
WFU
TIME:
Wednesday February 23, 2011 at 4:00 PM
PLACE: Room 101 Olin Physical Laboratory
Refreshments will be served at 3:30 PM in the Olin Lounge.
All interested persons are cordially invited to attend.
ABSTRACT
Nitric Oxide (NO) is a diatomic molecule with one unpaired electron which
makes it highly reactive. Because of its small size it can diffuse rapidly
through body tissues. These characteristics allow NO to function very well
as local signal transductor. NO plays an important role in the dilation of
blood vessels. It is produced in the endothelial cells which line the
inside of blood vessel walls. Smooth muscle tissue, which completely
surrounds blood vessels, can tense (contract) or expand (relax) to
decrease or increase the diameter of a blood vessel. Upon diffusion of NO
to the smooth muscle cells, a reaction cascade is activated which
eventually leads to smooth muscle relaxation and, hence, blood vessel
dilation. Abnormally low levels of bioavailable NO may lead to an
inability of smooth muscle to relax and to a subsequent increase in blood
pressure, and cause other deleterious effects. Hemoglobin, the
oxygen-carrying protein in blood, reacts rapidly with NO. Normally,
however, hemoglobin is encapsulated within red blood cells. This limits
its proximity to the endothelial cell layer, restricting its uptake rate
of NO. Several diffusional barriers are potentially responsible for this
rate limitation. The contribution of each of these barriers to the overall
rate reduction, compared with free hemoglobin, is currently under
investigation and is necessary to know in order to develop efficient blood
substitutes of membrane-encapsulated hemoglobin. In addition, there is
evidence that, under certain conditions, NO may be exported from within an
erythrocyte to affect vasodilation. When hemoglobin escapes red blood
cells its proximity to the endothelial cell layer is no longer restricted.
This results in increased scavenging of NO by hemoglobin and in an
impaired capacity of blood vessels to dilate. This occurs in hemolytic
diseases as well as during trasfusion of aged banked blood. The presented
work determines the rate limiting factors of NO uptake by
membrane-encapsulated hemoglobin under certain conditions, ways in which
NO uptake by cell-free hemoglobin may be prevented, and investigates some
possible mechanisms for NO export from within a red blood cell.
|
