Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade - Full Text View

Sponsor:	Medical University of Vienna
Information provided by:	Medical University of Vienna
ClinicalTrials.gov Identifier:	NCT00280462

Purpose

Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. For a long time it had been assumed that the choroid is a strictly passive vascular bed, which shows no autoregulation. However, recently several groups have identified some autoregulatory capacity of the human choroid. In the brain and the retina the mechanism behind autoregulation is most likely linked to changes in transmural pressure. In this model arterioles change their vascular tone depending on the pressure inside the vessel and outside the vessel. In the choroid, several observations argue against a direct involvement of arterioles. In a previous project we were able to identify that the nitric oxide (NO) - system as well as the endothelin system are involved in choroidal blood flow regulation during isometric exercise.

In the present study autoregulation of the choroid during isometric exercise will be investigated and the pressure/flow relationships will be observed in the absence or presence of a calcium antagonist - nifedipine.

Condition	Intervention
Ocular Physiology Regional Blood Flow	Drug: Nifedipine (drug) Drug: L-Arginin (drug) Drug: Placebo

Study Type:	Interventional
Study Design:	Allocation: Randomized Endpoint Classification: Safety/Efficacy Study Intervention Model: Crossover Assignment Masking: Double Blind (Subject, Investigator) Primary Purpose: Treatment
Official Title:	Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade

Resource links provided by NLM:

MedlinePlus related topics: Exercise and Physical Fitness

Drug Information available for: Nifedipine Arginine Arginine hydrochloride

U.S. FDA Resources

Further study details as provided by Medical University of Vienna:

Primary Outcome Measures:

Choroidal pressure-blood flow relationship [ Time Frame: in total 3x 3 hours ] [ Designated as safety issue: No ]

Enrollment:	21
Study Start Date:	August 2005
Study Completion Date:	April 2006
Primary Completion Date:	April 2006 (Final data collection date for primary outcome measure)

Arms	Assigned Interventions
Active Comparator: 1 Nifedipine	Drug: Nifedipine (drug) Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes Drug: L-Arginin (drug) L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes Drug: Placebo Placebo
Active Comparator: 2 L-Arginin	Drug: Nifedipine (drug) Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes Drug: L-Arginin (drug) L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes Drug: Placebo Placebo
Placebo Comparator: 3 Placebo	Drug: Nifedipine (drug) Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes Drug: L-Arginin (drug) L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes Drug: Placebo Placebo

Eligibility

Ages Eligible for Study:	19 Years to 35 Years
Genders Eligible for Study:	Male
Accepts Healthy Volunteers:	Yes

Criteria

Inclusion Criteria:

Men aged between 19 and 35 years, nonsmokers
Body mass index between 15th and 85th percentile (Must et al. 1991)
Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant
Normal laboratory values unless the investigator considers an abnormality to be clinically irrelevant
Normal ophthalmic findings, ametropy more than 3 Dpt.

Exclusion Criteria:

Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
Treatment in the previous 3 weeks with any drug
Symptoms of a clinically relevant illness in the 3 weeks before the first study day
History of hypersensitivity to the trial drug or to drugs with a similar chemical structure
History or presence of gastrointestinal, liver or kidney disease, or other conditions known to interfere with, distribution, metabolism or excretion of study drugs
Blood donation during the previous 3 weeks

Contacts and Locations

Please refer to this study by its ClinicalTrials.gov identifier: NCT00280462

Locations

Austria
Department of Clinical Pharmacology
Vienna, Austria, 1090

Sponsors and Collaborators

Medical University of Vienna

Investigators

Principal Investigator:

Gabriele Fuchsjäger-Mayrl, M.D.

Department of Clinical Pharmacology, Medical University of Vienna

More Information

No publications provided

Responsible Party:	Gabriele Fuchsjaeger-Mayrl, MD, Department of Clinical Pharmacology, Medical University of Vienna
ClinicalTrials.gov Identifier:	NCT00280462 History of Changes
Other Study ID Numbers:	OPHT-110705
Study First Received:	January 19, 2006
Last Updated:	July 8, 2008
Health Authority:	Austria: Federal Ministry for Health and Women

Keywords provided by Medical University of Vienna:

Nifedipine
Choroidal blood flow
Choroidal autoregulation
Isometric exercise

Additional relevant MeSH terms:

Nifedipine
Tocolytic Agents
Reproductive Control Agents
Physiological Effects of Drugs
Pharmacologic Actions
Therapeutic Uses

Calcium Channel Blockers
Membrane Transport Modulators
Molecular Mechanisms of Pharmacological Action
Cardiovascular Agents
Vasodilator Agents

ClinicalTrials.gov processed this record on February 09, 2012