title: Endocardial versus epicardial differences of intracellular free calcium under normal and ischemic conditions in perfused rat hearts.
abstract: Transmural heterogeneity of myocardial metabolism and function are present in the left ventricle under normal and ischemic conditions. To determine if endocardial versus epicardial differences of [Ca2+]i are also present, perfused rat heart studies using indo-1 fluorescence as an index of [Ca2+]i were performed in the left ventricular epicardium and endocardium. Hearts were studied during control conditions and low-flow ischemia. Results demonstrated the following: 1) At a pacing rate of 1.5 Hz, endocardial levels of diastolic and systolic [Ca2+]i (470 +/- 40 and 1,240 +/- 170 nM) were higher than epicardial levels (290 +/- 30 and 920 +/- 150 nM). 2) At a more physiological pacing rate of 5 Hz, endocardial levels of diastolic and systolic [Ca2+]i (680 +/- 50 and 1,230 +/- 70 nM) were also higher than epicardial levels (390 +/- 20 and 950 +/- 60 nM. 3) During low-flow ischemia, endocardial levels of diastolic [Ca2+]i rose to a greater degree (from 680 +/- 50 to 1,050 +/- 70 nM at 10% of control coronary flow) compared with epicardial levels (from 390 +/- 20 to 580 +/- 40 nM at 10% of control flow), suggesting that the endocardium is more susceptible to low-flow ischemia. 4) The amplitude of the [Ca2+]i transient was the same at the endocardium (540 +/- 50 nM) and epicardium (560 +/- 50 nM) and did not change during low-flow ischemia, despite marked contractile dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Medicine (Cardiology), University of California, San Francisco.
authors: V M
authors: VM
authors: Figueredo
authors: R
authors: R
authors: Brandes
authors: M W
authors: MW
authors: Weiner
authors: B M
authors: BM
authors: Massie
authors: S A
authors: SA
authors: Camacho
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003326:Coronary Circulation; D004699:Endocardium / Q000378:metabolism*; D005456:Fluorescent Dyes; D006321:Heart / Q000503:physiopathology; D066298:In Vitro Techniques; D007211:Indoles; D007425:Intracellular Membranes / Q000378:metabolism*; D008297:Male; D017202:Myocardial Ischemia / Q000378:metabolism* / Q000503:physiopathology; D009243:NAD / Q000378:metabolism; D010477:Perfusion; D010496:Pericardium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values
chemical_list: D005456:Fluorescent Dyes; D007211:Indoles; D009243:NAD; C048960:indo-1; D002118:Calcium