OBJECTIVE: On high salt intake, Dahl salt-sensitive rats develop cardiac hypertrophy disproportionate to the degree of hypertension. In the present studies, we assessed whether the cardiac hypertrophy induced by high salt depends on the development of hypertension per se, and leads to over-activity of the cardiac renin-angiotensin system (RAS). METHODS: Cardiac angiotensin converting enzyme (ACE) mRNA and activity, cardiac and plasma angiotensin I and II (AngI, II), as well as plasma renin activity (PRA) were assessed in Dahl salt-sensitive (Dahl S) and salt-resistant (Dahl R) rats on high (1370 micromol/g food) or regular salt (120 micromol/g food) diet for 2-5 weeks. Cardiac ACE and hypertrophic response in Dahl S on high salt were also assessed after central blockade of sympathetic hyperactivity and hypertension. RESULTS: In Dahl S rats, ACE mRNA and activity of the left ventricle (LV) increased markedly after 4-5 weeks of high salt diet compared with Dahl S on the control diet and Dahl R on either diet Chronic intra-cerebroventricular treatment with Fab fragments blocking brain 'ouabain' prevented the hypertension by high salt in Dahl S rats but did not affect the salt-induced increases in LV weight or in LV ACE mRNA and activity. On regular salt diet, Dahl S rats demonstrated significantly lower cardiac AngI and AngII than Dahl R rats. However, high salt intake did not cause significant changes in cardiac AngI and II in either strain. On regular salt diet, PRA, plasma AngI and II were all significantly lower in Dahl S versus R. In Dahl S rats, high salt did not cause further decreases of the already low PRA or plasma AngI and II. CONCLUSIONS: These data indicate a low activity of both circulatory and cardiac RAS in Dahl S versus R rats. The marked cardiac hypertrophy and increase in cardiac ACE mRNA and activity induced by high salt in Dahl S do not depend on the increase in blood pressure. High salt intake did not increase cardiac AngII in Dahl S, suggesting that the increase in ACE mRNA and activity may be relevant for non-angiotensinergic mechanisms involved in cardiac hypertrophy.
OBJECTIVE: On high salt intake, Dahl salt-sensitive rats develop cardiac hypertrophy disproportionate to the degree of hypertension. In the present studies, we assessed whether the cardiac hypertrophy induced by high salt depends on the development of hypertension per se, and leads to over-activity of the cardiac renin-angiotensin system (RAS). METHODS: Cardiac angiotensin converting enzyme (ACE) mRNA and activity, cardiac and plasma angiotensin I and II (AngI, II), as well as plasma renin activity (PRA) were assessed in Dahl salt-sensitive (Dahl S) and salt-resistant (Dahl R) rats on high (1370 micromol/g food) or regular salt (120 micromol/g food) diet for 2-5 weeks. Cardiac ACE and hypertrophic response in Dahl S on high salt were also assessed after central blockade of sympathetic hyperactivity and hypertension. RESULTS: In Dahl S rats, ACE mRNA and activity of the left ventricle (LV) increased markedly after 4-5 weeks of high salt diet compared with Dahl S on the control diet and Dahl R on either diet Chronic intra-cerebroventricular treatment with Fab fragments blocking brain 'ouabain' prevented the hypertension by high salt in Dahl S rats but did not affect the salt-induced increases in LV weight or in LV ACE mRNA and activity. On regular salt diet, Dahl S rats demonstrated significantly lower cardiac AngI and AngII than Dahl R rats. However, high salt intake did not cause significant changes in cardiac AngI and II in either strain. On regular salt diet, PRA, plasma AngI and II were all significantly lower in Dahl S versus R. In Dahl S rats, high salt did not cause further decreases of the already low PRA or plasma AngI and II. CONCLUSIONS: These data indicate a low activity of both circulatory and cardiac RAS in Dahl S versus R rats. The marked cardiac hypertrophy and increase in cardiac ACE mRNA and activity induced by high salt in Dahl S do not depend on the increase in blood pressure. High salt intake did not increase cardiac AngII in Dahl S, suggesting that the increase in ACE mRNA and activity may be relevant for non-angiotensinergic mechanisms involved in cardiac hypertrophy.
Authors: Markus P Schneider; Ulrike Raff; Christoph Kopp; Johannes B Scheppach; Sebastian Toncar; Christoph Wanner; Georg Schlieper; Turgay Saritas; Jürgen Floege; Matthias Schmid; Anna Birukov; Anke Dahlmann; Peter Linz; Rolf Janka; Michael Uder; Roland E Schmieder; Jens M Titze; Kai-Uwe Eckardt Journal: J Am Soc Nephrol Date: 2017-02-02 Impact factor: 10.121