Effects of Nitrite on Blood Vessel Dilation in Normal Volunteers
Status:
Completed
Trial end date:
2003-11-01
Target enrollment:
Participant gender:
Summary
Nitric oxide gas is important in regulating blood vessel dilation, and consequently, blood
flow. This gas is continuously produced by endothelial cells, which line the blood vessels.
This study will examine whether nitrite, a molecule that normally circulates in the blood
stream, can also dilate blood vessels. The results of this study may be valuable in
developing treatments for people with conditions associated with impaired endothelial
production of nitric oxide, including high blood pressure, high blood cholesterol, diabetes,
estrogen deficiency, and others.
Healthy, non-smoking normal volunteers 21 years of age or older may be eligible for this
study. People who lack the enzyme G6PD or cytochrome B5 in their red blood cells may not
participate. Absence of these enzymes can lead to episodes of sudden shortness of breath and
cyanosis (blueness of the skin due to lack of sufficient oxygen). Participants will undergo
the procedures described in study Parts A and B, as follows:
- Part A - After numbing the skin, small tubes are placed in the artery and vein at the
inside of the elbow of the dominant arm (right- or left-handed) and a small tube is
placed in a vein of the other arm. The tubes are used for infusing saline (salt water)
and for drawing blood samples. A pressure cuff is placed around the upper part of the
dominant arm, and a rubber band device called a strain gauge is also placed around the
arm to measure blood flow. When the cuff is inflated, blood flows into the arm,
stretching the strain gauge at a rate proportional to the flow. Grip-strength of the
dominant arm is measured with a dynamometer to determine maximum grip-strength. Then,
several measurements of blood flow, nitrite, hemoglobin, and handgrip are made before
and after administration of L-NMMA, a drug that blocks endothelial production of nitric
oxide.
- Part B - Part A testing is repeated, except that sodium nitrite dissolved in a saline
solution is infused into the artery of the forearm for a few minutes before and during
the hand-grip exercises. In addition, blood samples are drawn before and after each
handgrip exercise to measure methemoglobin, a substance that, at excessive levels, can
cause adverse side effects.