Reduced oxygen supply explains the negative force-frequency relation and the positive inotropic effect of adenosine in buffer perfused hearts

Autor(es)

Franchini, Kleber G. ; Marin, Rodrigo Miguel ^[2]

• Tipo de documento: Artigo Científico
• Fonte: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY; v. 289, n. 1, p. H131-H136, July 2005.
• Área do conhecimento: Ciências da Saúde - Medicina
• Assunto(s): Fisiologia Fisiologia cardiovascular

Resumo

In isolated rat hearts perfused with HEPES and red blood cell-enriched buffers, we examined changes in left ventricular pressure induced by increases in heart rate or infusion of adenosine to investigate whether the negative force-frequency relation and the positive inotropic effect of adenosine are related to an inadequate oxygen supply provided by crystalloid perfusates. Hearts perfused with HEPES buffer at a constant flow demonstrated a negative force-frequency relation, whereas hearts perfused with red blood cell-enriched buffer exhibited a positive force-frequency relation. In contrast, HEPES buffer-perfused hearts showed a concentration-dependent increase in left ventricular systolic pressure [EC50 = 7.0 ± 1.2 nM, maximal effect (Emax) = 104 ± 2 and 84 ± 2 mmHg at 0.1 µM and baseline, respectively] in response to adenosine, whereas hearts perfused with red blood cell-enriched buffer showed no change in left ventricular pressure. The positive inotropic effect of adenosine correlated with the simultaneous reduction in heart rate (r = 0.67, P < 0.01; EC50 = 3.8 ± 1.4 nM, baseline 228 ± 21 beats/min to a minimum of 183 ± 22 beats/min at 0.1 µM) and was abolished in isolated hearts paced to suppress the adenosine-induced bradycardia. In conclusion, these results indicate that the negative force-frequency relation and the positive inotropic effect of adenosine in the isolated rat heart are related to myocardial hypoxia, rather than functional peculiarities of the rat heart. (AU)

• Processo FAPESP: 01/11698-1 - Mecanismos de sinalização celular ativados por sobrecarga mecânica: implicações na hipertrofia e remodelamento miocárdicos
• Beneficiário: Kleber Gomes Franchini
• Modalidade de apoio: Auxílio à Pesquisa - Temático