Nitric oxide production is higher in rat cardiac microvessel endothelial cells than ventricular cardiomyocytes in baseline and hypoxic conditions: a comparative study.
The relative importance of endothelium- and cardiomyocyte-derived nitric oxide (NO) is unknown, with a lack of direct studies on cardiac microvessel endothelial cells (CMEC) and cardiomyocytes regarding relative cellular NO production.


OBJECTIVE
To assess and compare baseline and hypoxia-induced NO and ONOO- production in cardiomyocytes and CMEC.


METHODS
Rat cardiomyocytes were isolated, and cultured rat CMEC were purchased commercially. Hypoxia (+/- NOS inhibitors) was induced by mineral oil layering or hypoxic culture. NO and ONOO- were detected by FACS analysis of DAF-2/DA and DHR123, respectively. Total eNOS was determined by Western blot analysis.


RESULTS
1) Baseline NO production in CMEC was sevenfold (cultured cells) and 26-fold (isolated cells) higher than in cardiomyocytes, 2) eNOS expression was 22-fold higher in CMEC, 3) hypoxia increased NO production in both cell types, albeit to a larger extent in CMEC, 4) in hypoxic cardiomyocytes, nonselective NOS and iNOS-specific inhibition attenuated NO production, whereas in CMEC, iNOS-specific inhibition was ineffective, and 5) baseline ONOO- production was 2.2 times greater in CMEC than in cardiomyocytes.


CONCLUSIONS
Using a novel approach, this study demonstrated that CMEC produce more baseline NO than cardiomyocytes, and that hypoxia activates NOS to increase NO production in both cell types. Baseline eNOS content was higher in CMEC than in cardiomyocytes, suggesting that differences in baseline NO production were eNOS-associated.
Strijdom
Hans
H
Department of Medical Physiology and Biochemistry, Faculty of Health Sciences, Stellenbosch University, Tygerberg, Republic of South Africa. jgstr@sun.ac.za
Jacobs
Sean
S
Hattingh
Suzél
S
Page
Carine
C
Lochner
Amanda
A
D000818:Animals; D003331:Coronary Vessels / Q000166:cytology; D042783:Endothelial Cells / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III