Pilot Study On The Role Of Nitric Oxide In Alpha 1-Adrenergic Vasoreactivity

Study Overview
=================
Brief Summary
-----------------
This is a research project to test two study techniques among healthy adults. The procedures look at how blood flow is controlled by substances in blood vessels.

Detailed Description
-----------------
Most patients with chronic kidney disease (CKD) have high blood pressure and are at high risk for cardiovascular disease. High blood pressure can be partly caused by narrowing of blood vessels from high activity of the alpha1-adrenoceptor system in blood vessels. On the other hand, nitric oxide (NO), produced by the body, opposes the alpha 1-adrenoceptor system. NO widens blood vessels and prevents high blood pressure. We hypothesize that low availability of NO may be responsible for high activity of alpha 1-adrenoceptor system in patients with CKD. This protocol is a pilot study in healthy subjects to guide us in performing future studies in patients with CKD. The specific aims of the pilot study, in healthy people, are to 1) determine whether alpha 1-adrenoceptor vasoreactivity is reproducible and 2) determine alpha 1-adrenoceptor vasoreactivity with the NO clamp technique. To carry out these specific aims, we will consent and enroll healthy people with normal blood pressure. After a screening visit to confirm eligibility, subjects will be admitted to the General Clinical Research Center overnight for a study the following day. We will constrict the forearm blood vessels by giving different amounts of phenylephrine into the artery through a catheter. We will measure the subjects blood flow with venus plethysmography ( a measuring tool like a blood pressure cuff) while giving the phenylephrine. We will repeat the tests to see if we get the same results. Then, a research medication, L-NMMA, which blocks NO in the blood vessel, will be dripped into the same artery followed by another medication nitroprusside, which gives back NO, to restore normal forearm blood flow. This procedure is called the NO clamp technique and is used to measure the effects of NO. The phenylephrine concentrations and plethysmography will be repeated again to compare vessel narrowing before and during the NO clamp. This research will teach us how to perform future studies on the relationship between NO and the alpha 1-adrenoceptor system in patients with kidney disease.

Official Title
-----------------
Pilot Study On The Role Of Nitric Oxide In Alpha 1-Adrenergic Vasoreactivity

Conditions
-----------------
Blood Pressure

Intervention / Treatment
-----------------
* Drug: Regional phenylephrine arterial infusion, Nitric Oxide Clamp


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Healthy men and women: Age 18 to 55 years Who have Blood Pressure less than or equal to 120/80. Exclusion Criteria: Individuals with: Diabetes, lung disease Stomach disease, liver disease Blood vessel disease Kidney disease High blood pressure Heart disease Hereditary blood disorders Hematocrit (amount of red blood cells) less than 30%, Who smoke Women who are pregnant or lactating

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Other
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: phenylephrine infusion with and without nitric oxide clamp<br>Participants received phenylephrine infusion with saline followed by phenylephrine infusion with nitric oxide clamp | Drug: Regional phenylephrine arterial infusion, Nitric Oxide Clamp<br> <br> |

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Determine whether alpha 1-adrenoceptor vasoreactivity is reproducible |  |  | 
| Determine alpha 1-adrenoceptor vasoreactivity with the NO clamp technique |  |  | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Vasoreactivity, Blood Pressure, Nitric Oxide, L-NMMA, Phenylephrine, Nitroprusside