Angiotensin II acutely decreases myocardial stiffness: a protein kinase C and Na+/H+ exchanger-mediated effect.

• Type: Summary of Presentation in an International Conference
• Date: 2005

Authors

Castro-Chaves P (Author) FMUP; Pimentel-Nunes P (Author) FMUP; Lima-Carneiro A (Author) Other; Fontes-Carvalho R (Author) FMUP; Leite-Moreira AF (Author) FMUP

Conference proceedings International

Title: European Journal of Heart Failure

Initial page: 64

ESC Annual Congress 2005

Stockholm, Sweden , 03 a 07 de Setembro de 2005

Scientific classification

FOS: Medical and Health sciences > Other medical sciences

Other information

Resumo (PT): Acute effects of angiotensin II (AT-II) on the diastolic properties of the myocardium were only recently described. AT-II acutely increased myocardial distensibility through AT-1 receptor stimulation. In the present study we evaluated its effects on myocardial stiffness with passive length-tension relations and tried to clarify some of the underlying mechanisms. Increasing doses of AT-II (10e-9 to 10e-5 M) were added to rabbit right papillary muscles immersed in a modified Krebs solution (0.6 Hz, 1.8 mM Ca2+, 35°C) at baseline (n=11) and in presence of chelerythrine, a protein kinase C (pKC) inhibitor (CHE, 10e-5M; n=8), or 5-(N-methyl-N-isobutyl)-amiloride, an inhibitor of Na+/H+ exchanger (MIA; 10e-6 M; n=10). Calculated parameters: resting tension (RT), active tension (AT), peak rate of tension rise (dT/dtmax), resting length (RL) and peak shortening (PS). Results presented as mean±SEM in % of baseline (p<0.05). At baseline, AT-II induced a dose dependent positive inotropic effect and increased RL. At 10e-5 M, AT-II increased 43.3±6.25% AT, 58.6±9.6% dT/dtmax, 35.8±4.4% PS and 1.96±0.4% RL. Restoring RL to the value it presented before addition of AT-II resulted in a decrease in RT of 46±4%. In addition, AT-II right and downward shifted the passive length-tension relation (Figure). Effects of AT-II on RT were attenuated by MIA (23±5%) and almost blunted by CHE (11±4%). Passive length-tension relation In conclusion, AT-II significantly decreased RT and rightward shifted the passive length-tension relation, indicating a decrease in myocardial stiffness, an effect that was mediated by pKC and Na+/H+ exchanger. These results indicate that AT-II acutely modulates diastolic function and therefore may be involved in the response to acute changes in ventricular filling dynamics.

Language: English

Type (Professor's evaluation): Scientific

Notes: 27th Congress of the European-Society-of-Cardiology, published in journal, European Heart Journal. 2005; Vol.26 (Abstract P535)(Suppl1):64-64.