Angiotensin II infusions elevated blood pressure independently of platelet cytosolic calcium concentrations in humans.
A remarkably close correlation between platelet cytosolic calcium ([Ca2+i]) and arterial blood pressure has been identified in patients with essential hypertension. We tested the notion that a pharmacologically relevant infusion of angiotensin (Ang) II is associated with an increase in cytosolic calcium [Ca+2i]. Five normal volunteers received Ang II (5 ng/kg/min) for three hours or vehicle intravenously in random sequence respectively. The investigations were conducted at least 14 days apart. Plasma renin activity and blood pressure were measured every 20 minutes. [Ca+2i] was measured with the fluorescent indicator fura-2 before and at the end of the last hour of Ang II infusion. Mean arterial blood pressure increased by 10 mmHg during Ang II infusion (P < 0.05). Plasma renin activity decreased from 2.21 +/- 0.28 to 1.31 +/- 0.22 ng/ml/hour during the Ang II infusion (P < 0.05). On the other hand, [Ca+2i] was 131 +/- 13 nmol/l before and 129 +/- 13 nmol/l after the infusion (P = NS). The data suggest that agonists may increase blood pressure without an increase in platelet [Ca+2i]. Furthermore, Ang II may increase blood pressure independently of [Ca+2i].
Haller
H
H
Department of Internal Medicine, University Hospital-Steglitz, Germany.
Lenz
T
T
Oelkers
W
W
Luft
F C
FC
Distler
A
A
D000293:Adolescent; D000328:Adult; D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D001794:Blood Pressure / Q000187:drug effects*; D002118:Calcium / Q000097:blood*; D003600:Cytosol / Q000737:chemistry / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D011863:Radioimmunoassay; D012083:Renin / Q000097:blood
D000804:Angiotensin II; D012083:Renin; D002118:Calcium