The proposed studies focus on one aspect of myocardial injury, cardiac cell edema, and the underlying mechanisms of cell volume regulation. Lipid metabolites, including lysolipids derived from diacyl and plasmalogen species (e.g., lysophosphatidylcholine, lysoplasmenylcholine), long chain acylcarnitine, and arachidonic acid are reported to rapidly accumulate during ischemia and reflow and have been implicated in the ensuing electrophysiological disturbances. The central question to be evaluated here is: Do ischemic lipid metabolites disrupt cardiac cell volume regulation under isosmotic and anisosmotic conditions? It is postulated that lipid metabolites: (1) Cause cell swelling in the absence of an osmotic gradient by altering passive ion permeation and ion transport; (2) Exacerbate cell swelling in the presence of an osmotic gradient by increasing the permeability of cardiac cell membranes to water (i.e., hydraulic conductivity); and (3) Alter the response to swelling by modulating the function of stretch-activated channels and other ion permeation processes. The proposed experiments combine novel techniques to address the following aims: (1) The effects of lipid metabolites on cell volume under isosmotic conditions will be measured by digital video microscopy; (2) Hydraulic conductivity (water permeability) will be calculated from the kinetics of volume changes in response to osmotic stress; (3) Transport processes involved in lipid metabolite-induced volume changes will be identified by ion substitution studies and specific blockers; (4) Ion selective microelectrodes will be used to measure changes in the intracellular ion activities of K+, Na+, and Cl-; (5) The effect of metabolites on stretch- activated currents will be determined by simultaneous perforated-patch voltage clamp and cell volume measurements, and the magnitude of volume changes and currents will be related; and (6) The effects of lipid metabolites on sarcolemmal fluidity will be determined by fluorescence recovery after photobleaching (FRAP) in intact cells.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL046764-07
Application #
2750355
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Project Start
1991-08-16
Project End
2000-07-31
Budget Start
1998-08-01
Budget End
1999-07-31
Support Year
7
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Virginia Commonwealth University
Department
Physiology
Type
Schools of Medicine
DUNS #
City
Richmond
State
VA
Country
United States
Zip Code
23298
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Browe, David M; Baumgarten, Clive M (2006) EGFR kinase regulates volume-sensitive chloride current elicited by integrin stretch via PI-3K and NADPH oxidase in ventricular myocytes. J Gen Physiol 127:237-51
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Ren, Zuojun; Baumgarten, Clive M (2005) Antagonistic regulation of swelling-activated Cl- current in rabbit ventricle by Src and EGFR protein tyrosine kinases. Am J Physiol Heart Circ Physiol 288:H2628-36
Browe, David M; Baumgarten, Clive M (2004) Angiotensin II (AT1) receptors and NADPH oxidase regulate Cl- current elicited by beta1 integrin stretch in rabbit ventricular myocytes. J Gen Physiol 124:273-87
Du, Xin-Ling; Gao, Zhan; Lau, Chu-Pak et al. (2004) Differential effects of tyrosine kinase inhibitors on volume-sensitive chloride current in human atrial myocytes: evidence for dual regulation by Src and EGFR kinases. J Gen Physiol 123:427-39
Browe, David M; Baumgarten, Clive M (2003) Stretch of beta 1 integrin activates an outwardly rectifying chloride current via FAK and Src in rabbit ventricular myocytes. J Gen Physiol 122:689-702
Baumgarten, Clive M; Clemo, Henry F (2003) Swelling-activated chloride channels in cardiac physiology and pathophysiology. Prog Biophys Mol Biol 82:25-42
Li, Gui-Rong; Zhang, Min; Satin, Leslie S et al. (2002) Biphasic effects of cell volume on excitation-contraction coupling in rabbit ventricular myocytes. Am J Physiol Heart Circ Physiol 282:H1270-7
Li, G R; Baumgarten, C M (2001) Modulation of cardiac Na(+) current by gadolinium, a blocker of stretch-induced arrhythmias. Am J Physiol Heart Circ Physiol 280:H272-9

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