EFFECT OF RED-BLOOD-CELLS AND HEMOGLOBIN ON SPONTANEOUSLY HYPERTENSIVE AND NORMOTENSIVE RAT AORTAS

Experiments were designed to compare the contractile effect of red blo od cells (RBC) on aortic rings with and without endothelium from normo tensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Red blood cells of 4 week old WKY and SHR rats induced a negligible in crease in tension of aortic rings, either with or without endothelium, being slightly more effective in SHR rats. However, red blood cells o f 16 week old rats increased tension of WKY and SHR aortic rings, with endothelium at this age being more pronounced then red blood cells in 4 week old animals. The contractions induced by WKY and SHR red blood cells both in WKY and SHR aortic rings without endothelium at this ag e are significantly greater compared to the effect on aortic rings wit h endothelium. Red blood cell ghosts of rats of both strains increased the tension of the rings without endothelium of SHR aorta to near 50% of those induced by red blood cells, whereas they were ineffective in aortic rings without endothelium of WKY rats. Oxyhemoglobin increased the tension of 16 week SHR aortic rings both with and without endothe lium, whereas the effect on the rings of WKY rats was negligible. This increase in tension was inhibited by BM 13505, nordihydroguaiaretic a cid, and indomethacin in SHR rings both with and without endothelium, demonstrating an eicosanoid involvement in oxyhemoglobin-induced contr actions. Hemoglobin or its metabolites may be involved in development or in maintenance of spontaneous hypertensin. (C) 1998 American Journa l of Hypertension, Ltd.