Hiroaki Minamisawa

Brain eicosanoid levels in spontaneously hypertensive rats after ischemia with reperfusion: leukotriene C4 as a possible cause of cerebral edema.

The relation of brain eicosanoids to progression of cerebral edema was studied in stroke-resistant spontaneously hypertensive rats subjected to incomplete global brain ischemia induced by bilateral occlusion of the common carotid arteries. Thromboxane B2 and 6-keto prostaglandin F1 alpha levels were significantly elevated 5 minutes after reperfusion but returned to control levels by 30 minutes. In contrast, leukotriene C4 levels increased 2 hours after bilateral common carotid artery occlusion and peaked 30 minutes after reperfusion, with higher levels persisting until 60 minutes after reperfusion. Cerebral ischemia was accompanied by cerebral edema early after reperfusion. The edema correlated with increased leukotriene C4 levels. That the increased brain water content was causally related to an increase in leukotriene C4 was supported by results obtained following administration of the 5-lipoxygenase inhibitors ONO-LP-016 and AA-861. Both inhibitors suppressed the increased leukotriene C4 and brain water contents after reperfusion. Our results indicate that leukotriene C4 is closely associated with an induction of ischemic cerebral edema.

Increased intracellular Ca2+ concentration in the hippocampal CA1 area during global ischemia and reperfusion in the rat: a possible cause of delayed neuronal death

The crucial role of free cytosolic Ca2+ in ischemic neuronal damage has been studied in recent years. In the present report, changes in the intracellular Ca2+ concentration in the hippocampal CA1 area during transient global ischemia and reperfusion were measured using in vivo Ca2+ fluorometry with fura-2 in the four-vessel occlusion and reperfusion model in halothane-anesthetized rats. Marked changes were seen during 10-min global ischemia, with the intracellular Ca2+ concentration increasing gradually following application of the ischemic insult and rapidly about 2 min after the beginning of ischemia, and continuing to increase until reperfusion. On reperfusion, the intracellular Ca2+ concentration began to decrease and returned to the pre-ischemic level within 15 min. Induction of severe global ischemia was confirmed by the complete suppression of synaptic activity and the decrease in hippocampal temperature in the CA1 area. After seven days, CA1 pyramidal cell loss was observed histopathologically in the same rats which had undergone measurement of the intracellular Ca2+ concentration changes. In the present study, a temporal profile of the free cytosolic Ca2+ dynamics during ischemic and early post-ischemic period was determined in vivo. The results demonstrate that the intracellular Ca2+ concentration in the hippocampal CA1 area is transiently and markedly increased during a brief ischemia-inducing delayed neuronal death, implying that Ca2+ overload during cerebral ischemia is a possible cause of the delayed cell death of CA1 pyramidal neurons.

Changes of labile metabolites during anoxia in moderately hypo- and hyperthermic rats: correlation to membrane fluxes of K+.

The objective of this study was to assess the influence of temperature on the coupling among energy failure, depolarization, and ionic fluxes during anoxia. To that end, we induced anoxia by cardiac arrest in anesthetized rats maintained at a body temperature of either 34 degrees C or 40 degrees C, measured extracellular K+ concentration (K+e), and froze the neocortex through the exposed dura for measurements of phosphocreatine (PCr), creatine (Cr), ATP, ADP, and AMP, glucose, glycogen, pyruvate and lactate content after ischemic intervals of maximally 130 s. Free ADP (ADPf) concentrations were derived from the creatine kinase equilibrium. Hypothermia reduced the initial rate of rise in K+e, and delayed the terminal depolarization; however, both hypo- and hyperthermic animals showed massive loss of ion homeostasis at a K+e of 10-15 mM. The initial rate of rise in K+e did not correlate to changes in ATP, or ATP/ADPf ratio, suggesting that temperature changes per se may control the degree of activation of K+ conductances. The results clearly showed that, in both hyper- and hypothermic subjects, energy failure preceded the sudden activation of membrane conductances for ions. The results indicate that temperature primarily influences membrane permeability to ions like K+e (and Na+), and that cerebral energy state is secondarily affected. It is proposed that the higher rate of rise of K+e at high temperatures accelerates ATP hydrolysis primarily by enhancing metabolic rate in glial cells.

Plasma levels of leukotriene C4, B4 slow reacting substance of anaphylaxis in chloronological phases of cerebrovascular disease

In this study we report and compare plasma leukotriene (LT) levels in seventeen (17) patients with cerebral infarction, five (5) patients with cerebral hemorrhage and twelve (12) age-matched healthy volunteers. Plasma samples were collected at intervals of 1-7 days, 8-14 days, 15-30 days and 31 days- after cerebrovascular accident. Plasma immunoreactive LTC4, LTB4 and SRS-A (Slow Reacting Substance of Anaphylaxis or total peptido-LTs) levels were measured for each sample. Immunoreactive LTC4 (and SRS-A) levels were elevated in patients with cerebral infarction whilst LTB4 levels were raised in the patients with cerebral hemorrhage. In particular, cerebral infarcted patients exhibited significantly elevated levels in phases 1-7 days and after 15 days when compared with the age-matched healthy volunteers. In patients with cerebral hemorrhage, significant increases in LTB4 were measured in days 1-7 only. These results suggest a clinical relationship between the plasma levels of LTs and cerebrovascular disease.

Effects of vitamin A on eicosanoids production in the lung of rat treated by thermal injury.

After the treatment of thermal injury, contents of leukotriene C4 (LTC4) increased significantly at early stage and then kept the high level of LTC4 during the inflammation. Administration of vitamin A (VA) on vitamin A deficient- (AD) rats suppressed LTC4 induction in the lung and also inflammation and then gradually induced the significant decrease of LTC4 contents to the normal level 3 days after treatment of thermal injury. Synthesis of 6KPGF1α in the lung of AD rat was induced gradually until 24 hours after thermal injury. While the administration of VA to AD-rat enabled in the lung to induce the synthesis of 6-KPGF1α enough at early stage of thermal injury. After this induction, the production of 6KPGF1α gradually decreased. These results suggest that VA will suppress specifically the induction of lipoxygenase products but will not interfere the synthesis of cyclooxygenase products.

Studies on platelet cyclic nucleotide (c-AMP, c-GMP) levels in patients with cerebrovascular diseases

セカンドメッセンジャーであり血小板凝集反応に重要な役割を果していると考えられている血小板cyclic nucleotides (cyclic AMP, cyclic GMP) を脳血栓症, 脳出血の急性期および慢性期において検討した.また, 脳血管障害の基礎疾患である糖尿病についても検討した.cyclic AMPは, 脳血栓症では急性期においてコントロール群と比較し特に差異を認めなかったが, 慢性期では低値を示した.脳出血では急性期で高値をとる傾向を示し, 慢性期では低値を示した.糖尿病では有意の低値を示した.他方, cyclic GMPは脳血栓症では, 急性期および慢性期において高値をみた.脳出血においても急性期, 慢性期ともに高値であった.糖尿病ではコントロール群と比し差異を認めなかった.経時的変化の観察にて脳血栓症ではcyclicAMPは急性期にて一定した傾向を認めなかったが, cyclic GMPは高値をとり以後漸減した.脳出血では急性期にてcyclic AMP, cyclic GMPともに高値をとり, 以後漸次低下した.