title: Mechanism of blood pressure elevation during angiotensin infusion.
abstract: The mechanism of increased preload and its contribution to the rise in blood pressure during intravenous angiotensin infusion were studied in anesthetized dogs. In open-chest dogs angiotensin increased mean aortic blood pressure by 58 +/- 12 mmHg. Left ventricular end-diastolic dimension, measured as myocardial chord length (MCL) by ultrasonic technique, increased by 7 +/- 1%. By inflating a balloon in the inferior vena cava, end-diastolic MCL was reduced to control value and the rise in mean aortic blood pressure was almost halved to 32 +/- 10 mmHg above control value. A similar preload effect was recorded in closed-chest dogs using end-diastolic left ventricular pressure as an estimate of left ventricular volume. During angiotensin infusion to the upper body only, end-diastolic MCL did not increase. When redistribution of the splanchnic blood volume was prevented, the effect of angiotensin on end-diastolic MCL was reduced to 1/3. Angiotensin reduced liver but not splenic dimension measured by ultrasonic technique. We conclude that about half of the rise in blood pressure during angiotensin infusion is due to increased end-diastolic volume caused by blood redistribution. About 2/3 of this increase in preload is due to redistribution from the splanchnic bed, mainly from the liver.
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001810:Blood Volume / Q000187:drug effects; D004285:Dogs; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D007263:Infusions, Parenteral; D008099:Liver / Q000098:blood supply / Q000187:drug effects; D008297:Male; D013154:Spleen / Q000098:blood supply / Q000187:drug effects; D013318:Stroke Volume / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D000804:Angiotensin II