Phenotype of capillaries in skeletal muscle of nNOS-knockout mice

Baum, Oliver; Vieregge, Max; Koch, Pascale; Gül, Safak; Hahn, Sabine; Huber-Abel, Felicitas A. M.; Pries, Axel R.; Hoppeler, Hans (2013). Phenotype of capillaries in skeletal muscle of nNOS-knockout mice. American journal of physiology - regulatory, integrative and comparative physiology, 304(12), R1175-R1182. American Physiological Society 10.1152/ajpregu.00434.2012

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Because neuronal nitric oxide synthase (nNOS) has a well-known impact on arteriolar blood flow in skeletal muscle, we compared the ultrastructure and the hemodynamics of/in the ensuing capillaries in the extensor digitorum longus (EDL) muscle of male nNOS-knockout (KO) mice and wild-type (WT) littermates. The capillary-to-fiber (C/F) ratio (-9.1%) was lower (P ≤ 0.05) in the nNOS-KO mice than in the WT mice, whereas the mean cross-sectional fiber area (-7.8%) and the capillary density (-3.1%) varied only nonsignificantly (P > 0.05). Morphometrical estimation of the area occupied by the capillaries as well as the volume and surface densities of the subcellular compartments differed nonsignificantly (P > 0.05) between the two strains. Intravital microscopy revealed neither the capillary diameter (+3% in nNOS-KO mice vs. WT mice) nor the mean velocity of red blood cells in EDL muscle (+25% in nNOS-KO mice vs. WT mice) to significantly vary (P > 0.05) between the two strains. The calculated shear stress in the capillaries was likewise nonsignificantly different (3.8 ± 2.2 dyn/cm² in nNOS-KO mice and 2.1 ± 2.2 dyn/cm² in WT mice; P > 0.05). The mRNA levels of vascular endothelial growth factor (VEGF)-A were lower in the EDL muscle of nNOS-KO mice than in the WT littermates (-37%; P ≤ 0.05), whereas mRNA levels of VEGF receptor-2 (VEGFR-2) (-11%), hypoxia inducible factor-1α (+9%), fibroblast growth factor-2 (-14%), and thrombospondin-1 (-10%) differed nonsignificantly (P > 0.05). Our findings support the contention that VEGF-A mRNA expression and C/F-ratio but not the ultrastructure or the hemodynamics of/in capillaries in skeletal muscle at basal conditions depend on the expression of nNOS.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Anatomy
UniBE Contributor:	Baum, Oliver, Huber-Abel, Felicitas, Hoppeler, Hans-Heinrich
Subjects:	600 Technology > 610 Medicine & health 500 Science > 570 Life sciences; biology
ISSN:	0363-6119
Publisher:	American Physiological Society
Language:	English
Submitter:	Oliver Baum
Date Deposited:	02 May 2014 11:27
Last Modified:	05 Dec 2022 14:33
Publisher DOI:	10.1152/ajpregu.00434.2012
PubMed ID:	23576613
Uncontrolled Keywords:	capillary ultrastructure intravital microscopy neuronal nitric oxide synthase skeletal muscle vascular endothelial growth factor-A gene expression
URI:	https://boris.unibe.ch/id/eprint/51648