Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 286, Issue 1, Pages H222-H229Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00532.2003
Keywords
flow-mediated dilation; poloxamer coating
Funding
- FOGARTY INTERNATIONAL CENTER [R03TW001295] Funding Source: NIH RePORTER
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [R37HL015722, R01HL015722, P60HL048484] Funding Source: NIH RePORTER
- FIC NIH HHS [1R03-TW-01295] Funding Source: Medline
- NHLBI NIH HHS [HL-48484, HL-15722] Funding Source: Medline
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The effects of enhanced red blood cell (RBC) aggregation on nitric oxide (NO)dependent vascular control mechanisms have been investigated in a rat exchange transfusion model. RBC aggregation for cells in native plasma was increased via a novel method using RBCs covalently coated with a 13-kDa poloxamer copolymer (Pluronic F-98); control experiments used RBCs coated with a nonaggregating 8.4-kDa poloxamer (Pluronic F-68). Rats exchange transfused with aggregating RBC suspensions demonstrated significantly enhanced RBC aggregation throughout the 5-day follow-up period, with mean arterial blood pressure increasing gradually over this period. Arterial segments (approximate to300 mum in diameter) were isolated from gracilis muscle on the fifth day and mounted between two glass micropipettes in a special chamber equipped with pressure servo-control system. Dose-dependent dilation by ACh and flow-mediated dilation of arterial segments pressurized to 30 mmHg and preconstricted to 45-55% of the original diameter by phenylephrine were significantly blunted in rats with enhanced RBC aggregation. Both responses were totally abolished by nonspecific NO synthase (NOS) inhibitor (N-omega-nitro-L-arginine methyl ester) treatment of arterial segments, indicating that the responses were NO related. Additionally, expression of endothelial NOS protein was found to be decreased in muscle samples obtained from rats exchanged with aggregating cell suspensions. These results imply that enhanced RBC aggregation results in suppressed expression of NO synthesizing mechanisms, thereby leading to altered vasomotor tonus; the mechanisms involved most likely relate to decreased wall shear stresses due to decreased blood flow and/or increased axial accumulation of RBCs.
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