Inotropic responses to human gene 2 (B29) relaxin in a rat model of myocardial infarction (MI): Effect of pertussis toxin

Abstract

1. Relaxin produces powerful inotropic and chronotropic responses in isolated atria. The effect of relaxin has been examined in a rat model of cardiac failure, induced by myocardial infarction (MI). 2. Maximum inotropic responses to isoprenaline (sham 5.4±0.3 mN; MI 2.6±0.3 mN; P<0.001) and relaxin (sham 5.1±0.6 mN; MI 2.8±0.5 mN; P=0.013) were reduced in left atria following MI. No change in chronotropic responsiveness was observed in right atria. 3. Pertussis toxin (PTX) treatment restored inotropic responses to isoprenaline (sham 5.5±1.3 mN; MI 5.8±1.0 mN; P=0.850) but not to relaxin. Instead, PTX reduced inotropic responses to relaxin in sham animals to the same level seen in the MI grou..