The role of angiotensin II in hypertension due to adenosine receptors blockade.

The renin-angiotensin system may be involved in hypertension induced by adenosine receptors blockade with 1,3-dipropyl-8-sulfophenylxanthine (DPSPX). Contractions of the mesenteric vasculature to angiotensin II, noradrenaline and potassium chloride were studied in DPSPX-induced hypertension. Male Wistar rats received infusions of saline or DPSPX (90 microg kg(-1) h(-1), i.p.) for 3 or 7 days. Blood pressure was determined by the tail-cuff method. On days 3 or 14, concentration-response curves were obtained on mesenteric arteries and veins. Plasma angiotensin II levels, measured by radioimmunoassay, were higher in DPSPX-hypertensive rats. The maximum contractile effect of angiotensin II was lower in vessels from DPSPX-hypertensive rats while that for noradrenaline was higher. Potassium chloride-induced contractions were larger in veins from DPSPX-hypertensive rats but similar in arteries, when compared with control rats. We conclude that raised angiotensin II levels and altered vascular reactivity are consistent with a renin-angiotensin-mediated hypertension.