Effect of plasma on vessel tone and endothelial function

Abstract

The majority of isolated vessel experiments are performed with buffer or artificial cerebrospinal fluid in the lumen. Because the presence of plasma could affect vascular function and may be more physiological, we evaluated the influence of plasma on middle cerebral arteries (MCA). Arteries were isolated from male Wistar rats, mounted on glass cannulas in an arteriograph chamber and perfused with physiological saline solution (Ringer's PSS buffer; CTL, n=8) or with plasma (20% in buffer; PL, n=7) pooled from 5 normal rats. After 2 hours of equilibration at 75 mmHg myogenic tone and constriction to the NOS inhibitor L‐NNA (0.1mM) and the cyclooxygenase inhibitor indomethacin (10μM) were compared. The active diameters were significantly smaller at all pressures studied in arteries perfused with plasma than in CTL arteries (at 75mmHg: 243±9μm for CTL vs. 190±9μm for PL; p≤0.001). PL vessels also had greater basal myogenic tone compared with no plasma CTL (at 75mmHg: 10±3% for CTL vs 19±3% for PL; p≤0.05). The perfusion of plasma caused decreased constriction to L‐NNA (41±5% for CTL vs 19±3% for PL; p≤0.01) but did not affect constriction to indomethacin, suggesting the contribution of NO to tone is affected by plasma. In conclusion, there appear to be circulating factors in plasma that increase myogenic tone in the MCA, possibly though decreasing the contribution of NO. Supported by RO1NS043316 and PO1HL95488.