Direct vasopressor effects of erythropoietin in genetically hypertensive rats

The purpose of this study is to compare the direct vasopressor effects of erythropoietin between spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). The aortic rings from SHR or WKY were suspended in tissue baths coupled with tension-recording devices. High concentrations of recombinant human erythropoietin (more than 20 U/ml) induced vasoconstriction in the aortic ring of genetically hypertensive SHR. Furthermore, only in SHR, 10 U/ml erythropoietin enhanced contraction induced by 10(-7) M norepinephrine (+145% vs +121%, p < 0.04) and reduced relaxation by 10(-7) M acetylcholine (-69% vs -96%, p < 0.05). On the other hand, erythropoietin did not influence the contractility of aortic ring in normotensive WKY. These results suggest that erythropoietin exhibits its direct vasopressor effect preferentially in the blood vessels of genetically hypertensive animals.