Related Experiment Videos
Increased flow precedes remote arteriolar dilations for some microapplied agonists.
1Department of Anesthesiology, Biomedical Engineering Program, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA. molly_frame@urmc.rochester.edu
Summary
Remote responses in hamster cremaster muscles show that increased red blood cell (RBC) velocity often precedes arteriolar dilation. This suggests flow changes can initiate remote diameter adjustments.
Area of Science:
- Physiology
- Microcirculation
- Vascular Biology
Background:
- Understanding the sequence of events in remote vascular responses is crucial for comprehending microcirculatory regulation.
- Previous studies have explored local vascular responses, but the temporal relationship between flow and diameter changes at a distance remains less clear.
Purpose of the Study:
- To determine whether remote arteriolar dilation or a change in red blood cell (RBC) velocity occurs first in the hamster cremaster muscle.
- To investigate the role of specific agonists (LM-609, adenosine, SIN-1, papaverine) in initiating remote vascular responses.
Main Methods:
- Measurements of arteriolar diameter and RBC velocity in the hamster cremaster muscle using in vivo microscopy.
- Local stimulation of arterioles with agonists including an alpha(v)beta(3)-integrin agonist (LM-609), adenosine, a nitric oxide donor (SIN-1), and papaverine.
- Observation of vascular responses at a remote site located 1,200 microm upstream from the point of stimulation.
Main Results:
- LM-609 and adenosine caused an initial increase in RBC velocity within 5 seconds, followed by remote dilation 5-7 seconds later.
- N-nitro-L-arginine partially or fully blocked the remote dilations induced by LM-609 and adenosine, indicating a role for nitric oxide.
- The nitric oxide donor SIN-1 induced concurrent remote dilation and decreased RBC velocity, suggesting dilation as the primary event.
- Papaverine, a local dilator, did not elicit any remote effects.
Conclusions:
- Remote vascular responses can be initiated by primary signals leading to dilation, as seen with SIN-1.
- However, changes in blood flow dynamics (increased RBC velocity) can also precede and stimulate remote arteriolar diameter changes, as observed with LM-609 and adenosine.
- These findings highlight a dual mechanism in remote vascular regulation involving both direct signaling and flow-mediated adjustments.