Abstract

Our preliminary studies show that reoxygenation of single cardiac myocytes after brief or prolonged hypoxia causes functional abnormalities analogous to those seen in reperfused myocardium: prolonged relaxation, manifestations of calcium overload and, after long hypoxic periods, cell destruction. To study the mechanism of these changes, single myocytes, under direct observation, will be made hypoxic (PO2<0.02 torr) using the Laminar counterflow Barrier Well technique developed by the Sponsor and the Candidate. Changes in intracellular calcium will be measured using the fluorescent probe indo-1, intracellular pH using the new probe SNARF-1, and intracellular sodium using the new fluorescent crown ether SBFI. Mechanical shortening and membrane potential/currents will be measured simultaneously. By manipulating extracellular pH and sodium, intracellular pH (by varying PCO2) and phosphate (by pipette dialysis) we will test the hypothesis that post-hypoxic delayed relaxation is due to altered myofilament function, determine whether it can be accounted for by changes in intracellular pH and Pi, and test the hypothesis that sodium-calcium exchange, possibly linked to sodium-hydrogen exchange, is critical in the calcium-mediated destruction of cells reoxygenated after prolonged hypoxia.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08HL002539-04
Application #
2210147
Study Section
Research Manpower Review Committee (MR)
Project Start
1990-12-15
Project End
1995-11-30
Budget Start
1993-12-01
Budget End
1994-11-30
Support Year
4
Fiscal Year
1994
Total Cost
Indirect Cost

  Institution

Name
Johns Hopkins University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218

  Publications

Silverman, H S; Wei, S; Haigney, M C et al. (1997) Myocyte adaptation to chronic hypoxia and development of tolerance to subsequent acute severe hypoxia. Circ Res 80:699-707
Cave, A C; Adrian, S; Apstein, C S et al. (1996) A model of anoxic preconditioning in the isolated rat cardiac myocyte. Importance of adenosine and insulin. Basic Res Cardiol 91:210-8
Silverman, H S; Di Lisa, F; Hui, R C et al. (1994) Regulation of intracellular free Mg2+ and contraction in single adult mammalian cardiac myocytes. Am J Physiol 266:C222-33
Haigney, M C; Lakatta, E G; Stern, M D et al. (1994) Sodium channel blockade reduces hypoxic sodium loading and sodium-dependent calcium loading. Circulation 90:391-9
Bertoni, A G; Adrian, S; Mankad, S et al. (1993) Impaired posthypoxic relaxation in single cardiac myocytes: role of intracellular pH and inorganic phosphate. Cardiovasc Res 27:1983-90
Silverman, H S (1993) Mitochondrial free calcium regulation in hypoxia and reoxygenation: relation to cellular injury. Basic Res Cardiol 88:483-94
Miyata, H; Lakatta, E G; Stern, M D et al. (1992) Relation of mitochondrial and cytosolic free calcium to cardiac myocyte recovery after exposure to anoxia. Circ Res 71:605-13
Silverman, H S; Stern, M D; Lakatta, E G (1992) Contrasting effects of anoxia and graded hypoxia on single cardiac myocyte function. Am J Cardiovasc Pathol 4:256-64
Ziegelstein, R C; Zweier, J L; Mellits, E D et al. (1992) Dimethylthiourea, an oxygen radical scavenger, protects isolated cardiac myocytes from hypoxic injury by inhibition of Na(+)-Ca2+ exchange and not by its antioxidant effects. Circ Res 70:804-11
Haigney, M C; Miyata, H; Lakatta, E G et al. (1992) Dependence of hypoxic cellular calcium loading on Na(+)-Ca2+ exchange. Circ Res 71:547-57

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