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This Article Full Text Full Text (PDF) All Versions of this Article: 287/3/H1239    most recent 01155.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Savio-Galimberti, E. Articles by Ponce-Hornos, J. E. Search for Related Content PubMed PubMed Citation Articles by Savio-Galimberti, E. Articles by Ponce-Hornos, J. E.

Mechanical and energetic effects of chronic chagasic patients' antibodies on rat myocardium

¹Instituto de Investigaciones Cardiológicas, School of Medicine (Universidad de Buenos Aires-Consejo Nacional de Investigaciones Cientificas y Técnicas) and ²Biophysical Department, School of Dentistry, Universidad de Buenos Aires, 1122, Buenos Aires, Argentina; and ³Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21949-900 Rio de Janeiro, Brazil

Submitted 8 December 2003 ; accepted in final form 3 May 2004

Chagasic (Ch) and nonchagasic (NCh) IgG fraction (20 µg/ml) effects on cardiac performance of adult Wistar rat ventricles were studied with a novel approach applying a microcalorimetric technique. Resting heat (H_r) was significantly decreased by Ch antibodies (H_rCh = 4.8 ± 0.9 mW/g). Although the H_r decrease can be associated with diminished activity of the Na⁺/K⁺ pump, the magnitude of the effect (25% of control H_r) indicates that additional processes may also be affected. Ch antibodies induced an initial increase in developed pressure (P), which was associated with a decreased contractile economy. However, after 30 min of Ch antibody perfusion, P reached a significantly lower level (P_Ch = 3.8 ± 1.2 mN/mm²) without changes in active heat per beat (H_a). Consequently, H_a/P ratio increased, indicating that the energetic cost per unit of P was higher. In contrast, P and H_a were both significantly and reversibly decreased by NCh antibodies (P_NCh = 4.4 ± 1.2 mN/mm²; H_aNCh = 9.7 ± 2.2 mJ/g), but H_a/P remained unaffected. According to these data, normal hearts exposed to Ch antibodies present a biphasic mechanical response: 1) an initial period of increased contractility (and decreased global muscle economy) consistent with antibodies with ₁-adrenergic activity, such as those used in the present study, and 2) a decrease in P at 30 min of Ch antibody perfusion, which suggests that another Ca²⁺-related mechanism is compromised. These data contribute to redefine the role of antibody-mediated responses in the pathophysiology of chronic chagasic cardiomyopathy as agents of myocardial failure.

cardiomyopathy; energy metabolism; ventricular function; muscle economy; excitation-contraction coupling

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