The overall goal of this project is to determine the factors that regulate myocardial contractility during reductions of coronary flow. This goal will be accomplished by testing the following two-part hypothesis in isolated perfused rabbit hearts: .mild to moderate reductions of coronary flow. At coronary flow rates where oxygen availability is not rate-limiting for ATP synthesis, changes in the myocardial calcium transient primarily regulate myocardial contractility. .severe reductions of coronary flow. At coronary flow rates where oxygen availability is rate limiting for ATP synthesis, increases of inorganic phosphate (Pi) and/or H+ primarily regulate myocardial contractility by decreasing myofilament calcium sensitivity. To test this hypothesis, simultaneous measurements of the calcium transient, phosphates (ATP, phosphocreatine, Pi), intracellular pH, and myocardial contractility will be made during steady-state reductions of coronary flow and acute no-flow conditions. The calcium transient will be measured using indo-1, a fluorescent calcium indicator. Phosphates and intracellular pH will be measured using 31P NMR spectroscopy. The proposed experiments will provide new and important information regarding the mechanisms that regulate contractility during reductions of coronary flow.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08HL002448-02
Application #
3082864
Study Section
Special Emphasis Panel (SRC (KR))
Project Start
1990-07-01
Project End
1995-06-30
Budget Start
1991-07-01
Budget End
1992-06-30
Support Year
2
Fiscal Year
1991
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Medicine
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Chang, K C; Figueredo, V M; Schreur, J H et al. (1997) Thyroid hormone improves function and Ca2+ handling in pressure overload hypertrophy. Association with increased sarcoplasmic reticulum Ca2+-ATPase and alpha-myosin heavy chain in rat hearts. J Clin Invest 100:1742-9
Chang, K C; Schreur, J H; Weiner, M W et al. (1996) Impaired Ca2+ handling is an early manifestation of pressure-overload hypertrophy in rat hearts. Am J Physiol 271:H228-34
Figueredo, V M; Camacho, S A (1995) Basic mechanisms of myocardial dysfunction: cellular pathophysiology of heart failure. Curr Opin Cardiol 10:246-52
Brandes, R; Figueredo, V M; Camacho, S A et al. (1994) Compensation for changes in tissue light absorption in fluorometry of hypoxic perfused rat hearts. Am J Physiol 266:H2554-67
Camacho, S A; Brandes, R; Figueredo, V M et al. (1994) Ca2+ transient decline and myocardial relaxation are slowed during low flow ischemia in rat hearts. J Clin Invest 93:951-7
Brandes, R; Figueredo, V M; Camacho, S A et al. (1993) Quantitation of cytosolic [Ca2+] in whole perfused rat hearts using Indo-1 fluorometry. Biophys J 65:1973-82
Camacho, S A; Figueredo, V M; Brandes, R et al. (1993) Ca(2+)-dependent fluorescence transients and phosphate metabolism during low-flow ischemia in rat hearts. Am J Physiol 265:H114-22
Brandes, R; Figueredo, V M; Camacho, S A et al. (1993) Investigation of factors affecting fluorometric quantitation of cytosolic [Ca2+] in perfused hearts. Biophys J 65:1983-93