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Heterogeneity in cellular response and intracellular distribution of Ca2+ concentration during and after metabolic
H Hayashi1, H Miyata, A Kobayashi
1Third Department of Internal Medicine, Hamamatsu University School of Medicine, Japan.
Study Objective:
To characterise cell injury during myocardial hypoxia and reoxygenation, [Ca2+]i was measured in guinea pig ventricular myocytes using digital images of fura-2 fluorescence.
Design:
[Ca2+]i and cell morphology were measured during and after the perfusion of 2 mmol.litre-1 sodium cyanide (NaCN).
Experimental Material:
28 ventricular myocytes isolated from guinea pig hearts.
Measurements And Main Results:
Eight out of 28 cells became rounded during the perfusion with NaCN, and [Ca2+]i increased from 48 (SEM 6) nmol-litre-1 to 163(24) (p less than 0.01) before cell rounding, and to 311(46) (p less than 0.01) after cell rounding. Ten cells were rounded after the washout of NaCN, and [Ca2+]i increased to 252(41) nmol.litre-1 before cell rounding (p less than 0.01), and to 314(48) after cell rounding (p less than 0.01). Intracellular distribution of [Ca2+]i was heterogeneous in some cells with high [Ca2+]i. The values of [Ca2+]i before and after cell rounding, during and after the perfusion of NaCN, were significantly lower than those during the perfusion of strophanthidin (0.1 mmol.litre-1).
Conclusions:
There appeared to be a mixed population of myocytes, some showing normal [Ca2+]i and shape, and others showing high [Ca2+]i and contracture, during the perfusion or the washout of NaCN. Ca2+ overload alone is unlikely to be the main and the only mechanism of cell injury during myocardial hypoxia/reoxygenation. Other mechanisms such as membrane disturbance could be involved.