Myocardial enzymatic activity of renin and cathepsin D before and after bilateral nephrectomy |
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Authors: | Stephen A Katz John A Opsahl Lynn M Forbis |
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Institution: | (1) Department of Physiology, 6-125 Jackson Hall, University of Minnesota School of Medicine, 321 Church St. S.E., Minneapolis, MN 55455, USA, E-mail: katzx001@umn.edu, US;(2) Division of Nephrology, Hennepin County Medical Center, 701 Park Ave., Minneapolis, MN 55415, USA, US |
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Abstract: | A local renin-angiotensin system is present within the myocardium and can play a role in the initiation and maintenance of
cardiac hypertrophy. The source of myocardial renin may be direct cardiac renin gene expression, or plasma renin of renal
origin. A primary indication that myocardial renin is derived from plasma renin of renal origin was from work showing that
cardiac renin activity was no longer detected 30 hours after bilateral nephrectomy (BNX). However, more recent studies have
been able to detect myocardial renin after BNX.
We measured normal rat cardiac renin before and after 48-hour BNX using a myocardial renin assay with improved sensitivity.
The myocardial renin assay was also used to assess normal rat cardiac myocyte renin levels. Since cardiac tissue contains
cathepsin D, a lysosomal enzyme capable of renin-like activity, a rat cathepsin D assay was also developed to assess cathepsin
D contribution to renin-like activity.
Several artifacts were shown to contribute to myocardial renin-like enzymatic activity levels after BNX, including initial
plasma renin stimulation during BNX surgery, assay pH, and cardiac cathepsin D activity. Myocardial renin concentration after
48-BNX was found to be only ∼1 % of normal control levels, and renin concentration in normal cardiac myocytes was only 2-fold
greater than assay blanks. Both results were probably overestimated due to cathepsin D contamination. In conclusion, no evidence
was found for myocardial renin synthesis in the normal adult rat heart, and myocardial renin decays to near zero levels after
48-hour BNX.
Received: 5 March 2001, Returned for revision: 12 March 2001, Revision received: 9 April 2001, Accepted: 10 April 2001 |
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Keywords: | Renin-angiotensin system – cardiac myocytes – angiotensin – cardiac renin |
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