The broad objective of the proposed study is to determine the role of sympathetic activity and hemodynamic load on cardiac muscle performance, mass and contractile proteins. The rat heterotopic cardiac isograft is perfused by the same hormonal milieu as the native heart but hemodynamic load on the myocardium is reduced thereby allowing a careful study of the unloaded, denervated heart exposed to various external stimuli. Initial studies of the acute and chronic hemodynamic characteristics and coronary blood flow in the isograft will facilitate interpretation of subsequent experiments. In the isograft, myocardial catecholamines and myosin isoenzymes will be correlated with isolated papillary muscle mechanics from animals conditioned by chronic running or swimming to determine the degree to which the transplanted heart responds to circulating catecholamines. The role of heart rate on protein synthesis and mRNA of the isograft will be examined at several time points following transplantation. Heart rate of the isograft will be increased by external pacing at rates greater than the intrinsic heart rate. Myocardial infarction results in cell loss and compensation by the surviving tissue. Ventricular remodeling presumably occurs in response to an increased pressure load. Coronary ligation in the isograft will provide information on how the heart responds to a reduced hemodynamic load following segmental tissue loss.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
First Independent Research Support & Transition (FIRST) Awards (R29)
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Surgery and Bioengineering Study Section (SB)
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Montefiore Medical Center (Bronx, NY)
New York
United States
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Geenen, D L; Malhotra, A; Scheuer, J et al. (1997) Repeated catecholamine surges alter cardiac isomyosin expression but not protein synthesis in the rat heart. J Mol Cell Cardiol 29:2711-6
Evans, S M; Bergeron, M; Ferriero, D M et al. (1997) Imaging hypoxia in diseased tissues. Adv Exp Med Biol 428:595-603
Geenen, D L; Malhotra, A; Buttrick, P M (1996) Angiotensin receptor 1 blockade does not prevent physiological cardiac hypertrophy in the adult rat. J Appl Physiol 81:816-21
Geenen, D L; Malhotra, A; Buttrick, P M et al. (1994) Ventricular pacing attenuates but does not reverse cardiac atrophy and an isomyosin shift in the rat heart. Am J Physiol 267:H2149-54
Geenen, D L; Malhotra, A; Scheuer, J (1993) Angiotensin II increases cardiac protein synthesis in adult rat heart. Am J Physiol 265:H238-43