Endothelial Hyperpolarization in Humans

Study Overview
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Brief Summary
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The purpose of this study is to elucidate the role Endothelium-Derived Hyperpolarizing Factor (EDHF) plays in dilating blood vessels and whether it differs between healthy people and those with high cholesterol. A second purpose of the study is to determine the identity of EDHF.

Detailed Description
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The vascular endothelium synthesizes at least four potent vasodilator substances: nitric oxide (NO), prostacyclin, carbon monoxide and endothelium-derived hyperpolarizing factor (EDHF) that contribute to vasodilator tone, and to inhibition of platelet activation and inflammation. EDHF release is stimulated by receptor-dependent agonists such as acetylcholine and bradykinin (BK), and leads to hyperpolarization of the underlying smooth muscle cells presumably by opening Ca2+-activated K+ channels. Indirect pharmacological evidence suggests that EDHF is a cytochrome P450-derived arachidonic acid metabolite, presumably an epoxide. Although the pivotal role of NO to conduit vessel dilation in response to acute increases in shear stress is well known, its' contribution to dilation with sustained increases in flow are minimal, and may be due to EDHF release.

Official Title
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Physiology and Pathologic Role of Endothelium-Derived Hyperpolarizing Factor in Humans

Conditions
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Hyperlipidemia

Intervention / Treatment
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* Drug: Tetraethylammonium (TEA)
* Drug: L-NG-monomethyl Arginine (L-NMMA)
* Drug: Bradykinin
* Drug: Sodium nitroprusside
* Drug: Acetylcholine
* Drug: Saline
* Drug: Fluconazole


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Hyperlipidemic (LDL > 140) Healthy Volunteer Exclusion Criteria: Pregnancy Diabetes mellitus Cardiovascular Disease Hypertension Use of any regular medications Renal insufficiency Smoking (current or within the past 5 years) Bleeding disorder

Ages Eligible for Study
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Minimum Age: 21 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

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


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Healthy Controls<br>Healthy subjects had venous occlusion plethysmography after intra-arterial infusions of saline, L-NG-monomethyl Arginine (L-NMMA), Tetraethylammonium (TEA), fluconazole, bradykinin, sodium nitroprusside and acetylcholine | Drug: Tetraethylammonium (TEA)<br>* 5 minute intra-arterial infusion of Tetraethylammonium at 1 mg/min<br>Drug: L-NG-monomethyl Arginine (L-NMMA)<br>* 5 minute intra-arterial infusion of L-NMMA 8 μmol/min<br>* Other names: Methylarginine;Drug: Bradykinin<br>* Intra-arterial infusion of bradykinin at 100, 200, and 400 ng/min. Each dose will be given for 5 minutes.<br>Drug: Sodium nitroprusside<br>* Intra-arterial infusion of sodium nitroprusside at 1.6 and 3.2 mg/min. Each dose will be given for 5 minutes.<br>* Other names: Nitropress;Drug: Acetylcholine<br>* Intra-arterial infusion of acetylcholine at 7.5, 15 and 30 μg/min. Each dose will be given for 5 minutes.<br>Drug: Saline<br>* 5 minute intra-arterial infusion of 0.9% saline at 2.5ml/min<br>Drug: Fluconazole<br>* 5 minute intra-arterial infusion of fluconazole at 0.4 mg/L/min<br>* Other names: Diflucan;|
| Experimental: Risk Factors<br>Non-hypertensive subjects with cardiovascular risk factors had venous occlusion plethysmography after intra-arterial infusions of saline, L-NG-monomethyl Arginine (L-NMMA), Tetraethylammonium (TEA), fluconazole, bradykinin, sodium nitroprusside and acetylcholine | Drug: Tetraethylammonium (TEA)<br>* 5 minute intra-arterial infusion of Tetraethylammonium at 1 mg/min<br>Drug: L-NG-monomethyl Arginine (L-NMMA)<br>* 5 minute intra-arterial infusion of L-NMMA 8 μmol/min<br>* Other names: Methylarginine;Drug: Bradykinin<br>* Intra-arterial infusion of bradykinin at 100, 200, and 400 ng/min. Each dose will be given for 5 minutes.<br>Drug: Sodium nitroprusside<br>* Intra-arterial infusion of sodium nitroprusside at 1.6 and 3.2 mg/min. Each dose will be given for 5 minutes.<br>* Other names: Nitropress;Drug: Acetylcholine<br>* Intra-arterial infusion of acetylcholine at 7.5, 15 and 30 μg/min. Each dose will be given for 5 minutes.<br>Drug: Saline<br>* 5 minute intra-arterial infusion of 0.9% saline at 2.5ml/min<br>Drug: Fluconazole<br>* 5 minute intra-arterial infusion of fluconazole at 0.4 mg/L/min<br>* Other names: Diflucan;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percent Change in Forearm Blood Flow (FBF) After Tetraethylammonium (TEA) Administration | Simultaneous forearm blood flow (FBF) measurements were obtained in both arms using a dual-channel venous occlusion strain gauge plethysmograph at rest and after administration of tetraethylammonium (TEA). Flow measurements were recorded for approximately 7 seconds, every 15 seconds up to eight times and a mean FBF value was computed. Percent change is the difference from baseline FBF and after TEA administration. | Baseline, 5 minutes | 
| Percent Change in Forearm Blood Flow (FBF) After Administration of L-NG-monomethyl Arginine (L-NMMA) | Simultaneous forearm blood flow (FBF) measurements were obtained in both arms using a dual-channel venous occlusion strain gauge plethysmograph after administration of L-NG-monomethyl Arginine (L-NMMA). Flow measurements were recorded for approximately 7 seconds, every 15 seconds up to eight times and a mean FBF value was computed. Percent change is the difference in FBF from baseline and after L-NMMA administration. | Baseline, 5 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percent Change in Forearm Blood Flow (FBF) After Administration of L-NG-monomethyl Arginine (L-NMMA) and Tetraethylammonium (TEA) | Simultaneous forearm blood flow (FBF) measurements were obtained in both arms using a dual-channel venous occlusion strain gauge plethysmograph after administration of L-NG-monomethyl Arginine (L-NMMA) and Tetraethylammonium (TEA). Flow measurements were recorded for approximately 7 seconds, every 15 seconds up to eight times and a mean FBF value was computed. Percent change is the difference in FBF from after L-NMMA administration and after TEA administration. | 5 minutes, 10 minutes | 
| Percent Change in Forearm Blood Flow (FBF) After Fluconazole Administration | Simultaneous forearm blood flow (FBF) measurements were obtained in both arms using a dual-channel venous occlusion strain gauge plethysmograph at rest and after administration of fluconazole. Flow measurements were recorded for approximately 7 seconds, every 15 seconds up to eight times and a mean FBF value was computed. Percent change is the difference from baseline FBF and after fluconazole administration. | Baseline, 5 minutes | 
| Percent Change in Forearm Blood Flow (FBF) After L-NG-monomethyl Arginine (L-NMMA) and Fluconazole Administration | Simultaneous forearm blood flow (FBF) measurements were obtained in both arms using a dual-channel venous occlusion strain gauge plethysmograph after L-NMMA administration and administration of fluconazole. Flow measurements were recorded for approximately 7 seconds, every 15 seconds up to eight times and a mean FBF value was computed. Percent change is the difference in FBF after L-NMMA administration and then fluconazole administration. | 5 minutes, 10 minutes | 
| Percent Change in Forearm Blood Flow (FBF) After Fluconazole and Tetraethylammonium (TEA) Administration | Simultaneous forearm blood flow (FBF) measurements were obtained in both arms using a dual-channel venous occlusion strain gauge plethysmograph after administration of fluconazole and Tetraethylammonium (TEA) administration. Flow measurements were recorded for approximately 7 seconds, every 15 seconds up to eight times and a mean FBF value was computed. Percent change is the difference from FBF after fluconazole administration and after Tetraethylammonium (TEA) administration. | 5 minutes, 10 minutes | 
| Forearm Blood Flow (FBF) After Sodium Nitroprusside Administration | Simultaneous forearm blood flow (FBF) measurements were obtained in both arms using a dual-channel venous occlusion strain gauge plethysmograph after administration of sodium nitroprusside. Flow measurements were recorded for approximately 7 seconds, every 15 seconds up to eight times and a mean FBF value was computed. | 5 minutes | 
| Change in Tissue Plasminogen Activator (t-PA) Release | Individual net t-PA release at each time point were calculated by the following formula: net release = (Cv-CA) x {FBF x [101-hematocrit/100]}, where Cv and CA represent the concentration of t-PA in the brachial vein and artery, respectively. Change is the difference of t-PA at baseline and t-PA after bradykinin 400 ng/min | Baseline, 30 minutes | 
| Change in Tissue Plasminogen Activator (t-PA) Release After Tetraethylammonium (TEA) and Bradykinin Administration | Individual net t-PA release at each time point were calculated by the following formula: net release = (Cv-CA) x {FBF x [101-hematocrit/100]}, where Cv and CA represent the concentration of t-PA in the brachial vein and artery, respectively. Change is the difference of t-PA after Tetraethylammonium (TEA) and t-PA after bradykinin 400 ng/min | 30 minutes, 60 minutes | 
| Change in Tissue Plasminogen Activator (t-PA) Release After Fluconazole and Bradykinin Administration | Individual net t-PA release at each time point were calculated by the following formula: net release = (Cv-CA) x {FBF x [101-hematocrit/100]}, where Cv and CA represent the concentration of t-PA in the brachial vein and artery, respectively. Change is the difference of t-PA after fluconazole and t-PA after bradykinin 400 ng/min | 30 minutes, 60 minutes | 
| Change in Tissue Plasminogen Activator (t-PA) Release After Fluconazole, Tetraethylammonium (TEA), and Bradykinin Administration | Individual net t-PA release at each time point were calculated by the following formula: net release = (Cv-CA) x {FBF x [101-hematocrit/100]}, where Cv and CA represent the concentration of t-PA in the brachial vein and artery, respectively. Change is the difference of t-PA after fluconazole and tetraethylammonium (TEA) and t-PA after bradykinin 400 ng/min | 60 minutes, 90 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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hyperlipidaemia, EDHF, FMD