The evolution of infarction in the rat middle cerebral artery(MCA) occlusion model was examined by atomic absorption spectrometric measurements of Na, K and Ca concentrations in brain tissue samples. At 2, 4, 6, 8, and 24 hours after MCA
occlusion
and
sham occlusion the brain tissue samples were obtained. Tissue water concentrations were estimated from dry-wet weight measurement. The effects of nimodipine(2㎍/kg/min for 10 min) administered intravenously at 4 hours(Group A), 6 hours(Group B),
and 8
hours(Groups C) after MCA occlusion were investigated on both the size of infarction and tissue water, Na, K, and Ca concentrations at 24 hours.
@ES The results were as follows:
@EN 1) Normal concentrations of water, Na, K, and Ca averaged 0.793±0.009ml, 54.06±4.18μmole, 81.04±3.44 μmole, and 3.578±0.712 μmole/gm wet weight. At the infarct site by 24 hours, the changes of tissue water and ionic concentrations were
conspicuously evident so that water increased by more than 10%(P<0.005), Na increase by more than 120% (P<0.005), K decreased by more than 75%(P<0.005), and Ca increased by more than 200%(P<0.005).
2) The remarkable shifts of Na, K, and Ca concentrations occurred at 4-6 hours so that 60-85% of the ionic shifts developed by 6 hours. This characteristics of chronological ionic changes correlated well with the findings of 2% TTC staining
during
the
evolution of infarction. Water concentrations increased rapidly at 2-4 hours so that nearly 80% of water shift developed by 4 hours.
3) In group A(administered at 4 hours). nimodipine treatment siginficantly reduced both the ionic shifts at the infarct site and the size of infarction compared with non-treated rats(P<0.05).
4) In group B(administered at 6 hours), nimodipine treatment did not significantly reduce the ionic shifts but did reduce the size of infarction compare with non-treated rats(P<0.05).
In group C(administered at 8 hours), nimodipine treatment significantly reduced neither the ionic shifts nor the size of infarction.
In summary it was concluded that the progressive changes in tissue water and ionic concentrations developed at the infarct sites and the critical period of the changes was between 4 and 6hours, and nimodipine treatment was effective when
administered
within 4 hours. The results suggested that measurement of tissue ionic concentrations could be used as an alternative method for assessing tissue damage and a reliable method to quantify the tissue damage. This method may be useful for
determining
the
time window for therapeutic protocol, as well as for evaluating therapeutic effects.
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