title: Aspartate transporter expression and activity in hypertrophic rat heart and ischaemia-reperfusion injury.
abstract: This study's rationale was that the expression and activity of aspartate transporters in hypertrophied hearts might be different from normal hearts, which could affect the use of aspartate in myocardial protection of hypertrophied hearts. mRNA expression of system X(ag)(-) transporters in hearts from normal (Wistar Kyoto) and hypertrophied (spontaneously hypertensive rat) rats was investigated by RT-PCR. EAAT3 protein expression in isolated cells and vesicles from normal and hypertrophied hearts was investigated by Western blotting. The same vesicles were also used to measure aspartate uptake. The effects of 0.5 mmol l(-1) aspartate supplementation on cardiac performance during ischaemia-reperfusion were investigated in isolated and perfused hearts. Both normal and hypertrophied hearts expressed EAAT1 and EAAT3 mRNA. EAAT3 protein expression was significantly greater in cells and vesicles from hypertrophied hearts compared to normal hearts. The velocity (V(max)) of aspartate uptake was faster at 24.4 +/- 2.2 pmol mg(-1) s(-1) in vesicles from hypertrophied hearts compared to 8.2 +/- 0.8 pmol mg(-1) s(-1) (P < 0.001, t test, n= 6, means +/-s.e.m.) in normal heart vesicles. The affinity (K(m)) was similar for both preparations. When recoveries were matched, 0.5 mmol l(-1) aspartate addition reduced reperfusion injury and increased functional recovery of hypertrophied hearts but not normal hearts. This was associated with a greater preservation of ATP, glutamate and glutamine and less lactate production during ischaemia in aspartate-treated hypertrophied hearts compared to all other experimental groups. These results suggest that increased aspartate transporter expression and activity in hypertrophy helps facilitate aspartate entry into hypertrophied cardiomyocytes, which in turn leads to improved myocardial protection.
authors.affiliation: Bristol Heart Institute, University of Bristol, Bristol Royal Infirmary, Bristol BS2 8HW, UK. n.king@bris.ac.uk
authors.forename: Nicola
authors.initials: N
authors.lastname: King
authors.forename: Hua
authors.initials: H
authors.lastname: Lin
authors.forename: John D
authors.initials: JD
authors.lastname: McGivan
authors.forename: M-Saadeh
authors.initials: MS
authors.lastname: Suleiman
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000409:Alanine / Q000097:blood / Q000378:metabolism; D027322:Amino Acid Transport System X-AG / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism / Q000493:pharmacokinetics; D015153:Blotting, Western; D006332:Cardiomegaly / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D027341:Excitatory Amino Acid Transporter 1; D050580:Excitatory Amino Acid Transporter 3; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000097:blood / Q000378:metabolism; D005973:Glutamine / Q000097:blood / Q000378:metabolism; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D007511:Ischemia / Q000503:physiopathology; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D015424:Reperfusion; D015427:Reperfusion Injury / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012508:Sarcolemma / Q000737:chemistry / Q000378:metabolism; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D017725:Ventricular Pressure / Q000502:physiology
chemical_list: D027322:Amino Acid Transport System X-AG; D027341:Excitatory Amino Acid Transporter 1; D050580:Excitatory Amino Acid Transporter 3; D050491:Glutamate Plasma Membrane Transport Proteins; C493398:Slc1a1 protein, rat; C493392:Slc1a3 protein, rat; D027981:Symporters; D005973:Glutamine; D001224:Aspartic Acid; D019344:Lactic Acid; D018698:Glutamic Acid; D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase; D005969:Glutamate Dehydrogenase; D000409:Alanine