Makiko Azuma

Publications (2)4.38 Total impact

• Article: Preserved postischemic heart function in sucrose-fed type 2 diabetic OLETF rats.

  Hong Chen, Hideaki Higashino, Zdravko A Kamenov, Makiko Azuma, Wen-Hsiung Lee, Xiang-Qun Yang, Da-Jin Zhou, Wen-Jun Yuan
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  ABSTRACT: Cardiovascular disease is one of the most important causes of morbidity and mortality in diabetes mellitus, but there has been controversy over functional impairment of diabetic hearts and their tolerance to ischemia. We studied ischemic heart function in type 2 diabetic rats with different degrees of hyperglycemia and its relationship with cardiac norepinephrine release. Otsuka Long-Evans Tokushima Fatty rats (OLETF) and age-matched Long-Evans Tokushima Otsuka normal rats (LETO) were used. One group of OLETF rats was given 30% sucrose in drinking water (OLETF-S). Hearts were isolated and perfused in a working heart preparation and subjected to 30 min ischemia followed by 40 min reperfusion at age of 12 months. Hemodynamics and coronary norepinephrine overflow were examined. Fasting plasma glucose in OLETF increased markedly at 12 months and sucrose administration exacerbated hyperglycemia in diabetic rats (LETO 6.6 +/- 0.5, OLETF 8.3 +/- 0.7, OLETF-S 15.0 +/- 1.7 mmol/L, P < 0.01). Basic cardiac output in OLETF was decreased as compared with LETO and OLETF-S (LETO 29.4 +/- 2.5, OLETF 24.0 +/- 2.4, OLETF-S 27.0 +/- 0.9 ml/min/g, P < 0.05) and remained very low after ischemia, while in OLETF-S it was well preserved (OLETF 4.2 +/- 2.1, OLETF-S 13.7 +/- 2.6 ml/min/g, P < 0.01). Correspondently, cardiac norepinephrine released during ischemia and reperfusion was lower in OLETF-S (OLETF 2.3 +/- 1.0, OLETF-S 0.7 +/- 0.1 pmol/ml, P < 0.01). Thus, OLETF hearts were more vulnerable to ischemia but sucrose feeding rendered their hearts resistant to ischemia. Less norepinephrine release may play a role in preventing postischemic functional deterioration in sucrose-fed diabetic hearts.
  Life Sciences 05/2003; 72(25):2839-51. · 2.53 Impact Factor
• Article: Impaired Heart Function And Noradrenaline Release After Ischaemia In Stroke‐Prone Spontaneously Hypertensive Rats

  Hong Chen, Makiko Azuma, Kana Maeda, Noriyoshi Kajimoto, Hideaki Higashino
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  ABSTRACT: SUMMARY1. Stroke-prone spontaneously hypertensive rats (SHRSP) are a strain of rat that exhibit severely high blood pressure and stroke attacks at an early age, but their heart function in vitro has seldom been studied in detail. Although the activity of the sympathetic nervous system is known to increase after myocardial ischaemia, there is little information about the cardiac release of noradrenaline (NA) associated with heart function after ischaemia in SHRSP. The aim of the present study was to examine heart function and cardiac NA release after ischaemia in SHRSP.2. Isolated hearts of 4- and 8-month-old SHRSP and age-matched Wistar-Kyoto (WKY) rats were perfused in a working heart preparation and were subjected to 30 min ischaemia followed by 30 min reperfusion. Heart function and coronary flow were monitored throughout the experiment. Coronary effluent was collected for determination of NA using high- performance liquid chromatography coupled with electrochemical detection.3. Under baseline conditions, cardiac output of 4-month-old SHRSP was slightly but significantly decreased compared with that of WKY rats (P < 0.05), although coronary flow was maintained normally at this age. Eight-month-old SHRSP showed a further impairment of systolic heart function, with lower coronary flow and higher coronary vascular resistance under baseline conditions. Elevated left ventricular end-diastolic pressure was evident in SHRSP at both ages before ischaemia. Heart function was severely damaged after 30 min global ischaemia in SHRSP from both age groups. Stroke-prone spontaneously hypertensive rats also showed lower coronary flow and higher coronary vascular resistance during reperfusion.4. Coronary NA was not detectable in WKY rats or SHRSP at 4 months of age under baseline conditions. In 8-month-old SHRSP, pre-ischaemic NA release was significantly higher than that in age-matched WKY rat controls. The concentration of NA in the coronary effluent of SHRSP during reperfusion was also significantly higher than that of WKY rats at both ages.5. These data demonstrate that SHRSP have early impairment of both systolic and diastolic heart function compared with WKY rats. Severe damage of heart function and coronary flow after ischaemia in SHRSP was accompanied with an increased release of NA, which may play a harmful role in heart function impairment in SHRSP after ischaemia.
  Clinical and Experimental Pharmacology and Physiology 09/2000; 27(9):664 - 670. · 1.85 Impact Factor