Correlation between ptiO₂ and Apoptosis in Focal Brain ischaemia and the Influence of Systemic Hypertension

Czech version

Authors: F. Otevřel ¹; M. Smrčka ²; Š. Kuchtíčková ¹; J. Mužík ³
Authors‘ workplace: Ústav normální a patologické fyziologie LFMU Brno ¹; Neurochirurgická klinika FN Brno, pracoviště Bohunice ²; Centrum biostatistiky a analýz LFMU Brno ³
Published in: Cesk Slov Neurol N 2007; 70/103(2): 168-173
Category: Original Paper

Overview

Introduction:
Current neurosurgery and intensive medicine often deal with patients threatened by focal brain ischemia. Temporary ischemia has been used purposefully in some neurosurgical interventions. In the centre of ischemia, the tissue is menaced with necrosis but in the surrounding tissue (penumbra) the cells become extinct via apoptosis. Systemic hypertension can delay the extinction of cells by apoptosis in the tissue in the penumbra region probably by means of involving leptomeningeal collaterals.

Material and Methods:
We have used a thread model of focal brain ischemia in a sewer-rat which enables to perform controlled focal ischemia for the selected interval with long-term reperfusion. The effects of systemic hypertension on partial O₂pressure in the penumbral tissue and the number of cells disappearing via apoptosis were studied by means of TUNEL test. The total of 70 sewer-rats were operated on, which had been divided into groups of normotensive and hypertensive animals and then into groups with 15 or 30 minutes of focal ischemia. Reperfusion lasted for 48 hours.

Results:
Significant difference (p < 0.001) was demonstrated between normotensive and hypertensive groups with 15-minutes´ ischemia both in the values of p_tiO₂and decrease of the number of TUNEL+ cells, namely in favour of hypertensive rats. The comparison of 15-minutes´ normotensive and 30-minutes´ hypertensive ischemias showed an interesting significant difference in the initial and terminal values of p_tiO₂ (p < 0.001) in favour of hypertension but the decrease of p_tiO₂ is not significantly different (p = 0.141). TUNEL+ neurons of the cortex were fewer in number in the hypertensive group (p = 0.005).

Conclusion:
Systemic hypertension delays the extinction of cells via apoptotis in the tissue in the penumbra region. The number of TUNEL+ cells depends rather on the absolute value of p_tiO₂ than on the size of decrease in values during ischemia. Monitoring p_tiO₂ in clinical practice can also serve as an indicator of threatening the brain tissue with apoptosis.

Key words:
Brain focal ischemia, reperfusion, tissue oxymetry, apoptosis, sewer-rat, hypertension

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