Abstract

Intracellular calcium ([Ca++]ic) overload is the key factor for myocardial ischemia reperfusion injury(IR), however there was no report for interstitial Ca++ concentration ([Ca++]ex) dynamics. This research aims to plot the [Ca++]ex dynamics in rat myocardial IR in vivo. A microdialysis system was composed and the time delay of the system, recovery time, was introduced and tested with a fluids switching method. Twelve SD rats were divided into IR or control group. Myocardial IR was induced by ligating (20 min) or releasing (60 min) the suture underlying LAD. Mycrodialyisis probe was implanted into the left ventricular myocardium perfusion area to be occluded. Dialysate samples were collected every 10 min. Blood samples were drawn at the beginning and at the end of the procedures. Dialysate calcium concentration ([Ca++]i) was detected with an atomic absorption spectrophotometer. Serum calcium and cTnT were detected. Results revealed recovery time for the microdialysis system was 20 min, recovery rate was 16%. [Ca++]i showed no changes during ischemia and descended immediately after reperfusion, reached the lowest level at 20 min after reperfusion, then escalated slowly while keeping lower than control with significant difference. There was no difference in serum calcium at the beginning (control vs IR, mmol/L: 2.35±0.31 vs 2.63±0.2, p=0.093) and ending point (control vs IR, mmol/L: 2.38±0.34 vs 2.66±0.15, p=0.095). Serum cTnT of both groups showed no difference at the beginning (control vs IR, ng/mL: 0.47±0.38 vs 0.74±0.46, p=0.287) and rose respectively at the 60 min after reperfusion (control vs IR, ng/mL: 1.62±0.6 vs 4.29±2.22, p=0.031). Given the recovery time and recovery rate, baseline of rat myocardial [Ca++]ex was estimated as 1.26±0.22 mmol/L and the [Ca++]ex was speculated steady in ischemia, descending 33% at the start of reperfusion, then escalating slowly. Thus it can be inferred that recovery time was an important parameter for mycrodialysis technique, which should not be neglected and need to be tested. Our data suggest that [Ca++]ex in rat myocardial IR in vivo kept steady in ischemia, descended rapidly at the initial reperfusion then rebounded slowly.

Key words: Myocardium, ischemia, reperfusion, calcium, microdialysis.