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The role of the kidney in canine blood pressure control: direct assessment of the closed‐loop gain.
Author(s) -
Persson P B,
Ehmke H,
Kirchheim H R,
Lempinen M,
Nafz B
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019626
Subject(s) - blood pressure , loop gain , loop (graph theory) , kidney , closed loop , medicine , cardiology , mathematics , physics , engineering , control engineering , quantum mechanics , voltage , combinatorics
1. The feedback control of arterial blood pressure by the kidney in the range of hours was investigated in resting, conscious foxhounds. 2. A servo‐control device (connected to an aortic occlusive cuff implanted above both renal arteries) was used to maintain a constant pressure difference of 20 mmHg between aortic pressure measured proximal (mean arterial blood pressure: MAP) and distal (renal artery pressure: RAP) to the aortic cuff. 3. Protocol 1 (n = 6) served as a 4 h time control without intervention, protocol 2 (n = 6) consisted of three periods: after a control of 20 min duration, the servo‐control device was activated for 180 min; this was followed by a recovery period of 40 min. Protocol 3 (n = 6) was as protocol 2, but during converting‐enzyme inhibition. 4. Servo‐control increased plasma renin activity (PRA) transiently from 0.5 ng angiotensin I (AI) ml‐1 h‐1 to a peak value of 2.4 ng AI ml‐1 h‐1, subsequently both RAP and MAP rose to reach a new steady state. During this increase in RAP, PRA declined to 1.4 ng AI ml‐1 h‐1. 5. On average, the compensation of the pressure decrease sensed by the kidney amounted to 63% of the error signal (closed‐loop gain of 0.63 +/‐ 0.1). 6. Converting‐enzyme inhibition reduced this closed‐loop gain significantly (protocol 2 vs. protocol 3, 0.63 +/‐ 0.1 vs. 0.15 +/‐ 0.1; P < 0.05). 7. It is concluded, that the kidney plays an important role in medium‐term blood pressure regulation, most probably via the renin‐angiotensin system.