0
Views
0
CrossRef citations to date
0
Altmetric
Original

Changes in Capillary Shear Stress in Skeletal Muscles Exposed to Long-Term Activity: Role of Nitric Oxide

, , , &
Pages 249-259 | Received 25 Sep 2005, Accepted 21 Nov 2005, Published online: 10 Jul 2009
 

Abstract

Objective: The purpose of this study was to establish whether suppression of angiogenesis by nitric oxide synthase (NOS) inhibition in skeletal muscles exposed to long-term activity can be explained by changes in capillary shear stress linked to the lack of nitric oxide production.

Methods: Capillary shear stress was calculated from diameters (d) and red blood cell velocities (Vrbc) measured at rest and after acute contractions in epi-illuminated extensor digitorum longus muscles of control rats and those in which ankle flexors had been stimulated via implanted electrodes (10 Hz, 8 h · day−1) for 2 or 7 days without and with inhibition of nitric oxide synthase activity by Nω-nitro-L-arginine (L-NNA, 3–4 mg·day−1 in drinking water).

Results: Neither chronic electrical stimulation nor L-NNA treatment altered capillary diameters. Capillary Vrbc and shear stress (SS) were doubled in muscles after 2 days stimulation (298 ± 22 μm · s−1 and 11.4 ± 1.0 dyne · cm−2, respectively, p < .005) compared to controls (148 ± 18 μm · s−1 and 5.6 ± 0.8 dyne·cm−2) but normalized after 7 days (153 ± 27 μm · s−1 and 6.2 ± 1.0 dyne·cm−2), when the capillary bed is known to be enlarged. L-NNA, which increased blood pressure in all treated animals, abolished the increase in capillary SS after 2 days stimulation and decreased SS after 7 days.

Conclusions: These data support a role for NO in the early elevation of capillary shear stress that initiates angiogenesis in stimulated muscles, likely via modulation of upstream vascular resistance, and could explain the lack of capillary growth in stimulated muscles when nitric oxide generation is suppressed.

Supported by DFG FOR 341 TP1 and 12. We thank Sabine Hahn for her expert help with animal operations and handling, and Ing Nietert for help with keeping the programmed stimulators in a good order.

Reprints and Corporate Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

To request a reprint or corporate permissions for this article, please click on the relevant link below:

Academic Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

Obtain permissions instantly via Rightslink by clicking on the button below:

If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.