In vivo Staining of Apoptosis by Manganase-Enhanced Magnetic Resonance Imaging(MEMRI) in the Hypoxic-Ischemic Newborn Rat

J. T. Kim, K. H. Lim, H. J. Cho, J. H. Lee, K. S. Kim University of Ulsan College of Medicine, seoul, Korea, Republic of, Asan Institute for Life Sciences, seoul, Korea, Republic of, Sungkyunkwan University School of Medicine, seoul, Korea, Republic of Purpose It is well known that apoptosis is a major pathophysiology of hypoxic-ischemic brain injury in newborn rats [1]. Calcium influx to intracellular space is an important mechanism for apoptosis during hypoxic brain injury. Based on the notion that manganase (Mn) is an analogue for calcium ion (Ca) in many biological systems [2, 3], we hypothesized that Mn may enter the intracellular space through the calcium channel during the active stage of apoptosis and that those apoptotic cells may be detectable by MEMRI [4]. This study was purposed to see whether MEMRI can detect apoptosis for the hypoxic-ischemic newborn rat brain in vivo. Methods Animal Preparation: Neonatal rats (Sprague-Dawley, 7 day olds, 12-16g, n=18) were divided into 3 groups: Group 1 (n=6), hypoxic-ischemia with Mn administered; Group 2 (n=6), hypoxic-ischemia without Mn administered; and Group 3 (n=6), controls with Mn administered. Hypoxicischemia was induced by ligation of right common carotid artery under anesthesia with 2% isoflurane followed by a short recovery for 2 hours under normal air. Hypoxia was induced by exposer to 8% oxygen for 3 hours after the recovery period. Intraperitoneal injection of 120mM isotonic MnCl2 solution (87.5mg/kg) was given to the animals 24 hours before the hypoxicischemic injury. MEMRI: All MRI experiments were performed on a horizontal 4.7T/30 cm magnet interfaced to a Bruker Avance MRI console (Bruker Biospin, Ettlingen, Germany), and equipped with a 20 cm gradient set capable of supplying up to 100 mT/m. A birdcage coil (72mm i.d.) for transmitting and a saddle-backed surface coil (15mm i.d.)