Background-Induction of heat-shock proteins (HSPs) results in cardioprotection against ischemic insult. Geranylgeranylacetone (GGA), known as an antiulcer agent, reportedly induces HSP72 in the gastric mucosa and small intestine of rats. The present study tested the hypothesis that oral GGA would induce HSP72 in the heart and thus render cardioprotection against ischemia/reperfusion injury in rats. Methods and Results-Cardiac expression of HSPs was quantitatively evaluated in rats by Western blot analysis. Ten minutes of whole-body hyperthermia induced HSP72 expression in the rat hearts. A single oral dose of GGA (200 mg/kg) also induced expression of HSP72, which peaked at 24 hours after administration. Therefore, isolated perfused heart experiments using a Langendorff apparatus were performed 24 hours after administration of 200 mg/kg GGA (GGA group) or vehicle (control group). After a 5-minute stabilization period, no-flow global ischemia was given for 20, 40, or 60 minutes, followed by 30 minutes of reperfusion. During reperfusion, the functional recovery was greater and the released creatine kinase was less in the GGA group than in the control group. Electron microscopy findings revealed that the ischemia/reperfusion-induced damage of myocardial cells was prevented in GGA-treated myocytes. Conclusions-The results suggest that oral GGA is cardioprotective against ischemic insult through its induction of

Objectives:The aim of this study was to investigate the effects of the menstrual cycle on QT interval dynamics and the autonomic tone in healthy women.Methods: Holter ECGs were recorded in 11 healthy women aged 18-32 years during the follicular and luteal phases of their regular menstrual cycle. The interval from QRS onset to the apex (QaT) and to the end of the T-wave (QeT), the interval between the apex and the end of the T-wave (Ta-e), and RR intervals were measured automatically in the course of 24 hours by Holter ECGs. The QeT/RR, QaT/RR, and Ta-e/RR relationships were evaluated in each subject. The autonomic tone was assessed by the serum catecholamine level at rest and heart rate variability was measured by Holter ECGs.Results: (1) The follicular and luteal phases did not differ significantly with respect to the slopes of the QeT/RR, QaT/RR, and Ta-e/RR relationships. However, QeT and QaT intervals were significantly shorter for all RR intervals in the luteal than in the follicular phase (P < 0.0001). (2) The serum progesterone concentration was significantly higher in the luteal than in the follicular phase (P < 0.001). (3) Noradrenaline was significantly higher in the luteal than in the follicular phase (P < 0.05). There was no significant difference in the follicular and luteal phases with respect to heart rate variability measurements.Conclusions: Our results suggest that the menstrual cycle affects the QT intervals. The observed shorter QT interval during the luteal than the follicular phase may be attributable to the increase in serum progesterone and sympathetic tone. (PACE 2006; 29:607-613) QT interval, menstrual cycle, sex hormone, gender difference, QT/RR relationship, autonomic tone IntroductionPrevious studies have reported a gender difference in the incidence of various types of ventricular arrhythmias. Torsades de pointes associated with long QT syndrome is more common in women than in men, 1-3 whereas the incidence of Brugada syndrome 4 or sudden death 5 is higher in men than in women. We reported that genderspecific differences exist in the incidence of various types of idiopathic ventricular tachycardia (VT) and that VT originating from the right ventricular outflow tract (RVOT) is more common in women than in men. 6 It is important to consider the potential significance of endogenous, menstrual cycle-related sex hormones in various cardiovascular diseases. 7,8 The early follicular phase, during which serum estrogen is at its lowest level in the menstrual cycle, might be a time when premenopausal women with coronary artery disease are particularly susceptible to ischemic events. 7,8 On the other hand, Marchlinski et al. 9 reported that the hormonal flux that occurs during pre-

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Gender-specific differences exist in the incidence and age distribution of the various types of idiopathic VT. Studies on gender-specific differences in arrhythmia will lead to a better understanding of its mechanism(s) and provide valuable information for the development of optimal treatment strategies.

Our results indicate that essential hypertension acts synergistically with type 2 diabetes to depress cardiac reflex vagal and sympathetic function, and the results also suggest that insulin resistance may play a pathogenic role in these processes.