POTENTIAL ADVANTAGE OF REPAGLINIDE MONOTHERAPY IN GLYCEMIC CONTROL IN PATIENTS WITH TYPE 2 DIABETES AND SEVERE RENAL IMPAIRMENT.

CONTEXT: Oral anti-diabetic drugs (OADs) are leading option for treatment of type 2 diabetes (T2D). However, availability of OADs are limited in the presence of renal impairment (RI). OBJECTIVE: In this study, we examined the efficacy of repaglinide, which is mainly metabolized and excreted via non-renal route, in patients with T2D and severe RI that consists mainly of chronic kidney disease (CKD) stage 4. DESIGN SUBJECTS AND METHODS: This was an open label, single arm, interventional study by repaglinide monotherapy. The primary efficacy end point was HbA1c change from baseline to week 12. RESULTS: Repaglinide treatment significantly reduced HbA1c levels from 7.7 ± 0.7% to 6.1 ± 0.3% (p<0.001) in 9 patients with severe RI (mean estimated glomerular filtration rate was 26.4 ± 7.5 mL/min/1.73m2). Focusing on 4 patients who received DPP-4 inhibitor monotherapy at enrolment, switching to repaglinide also significantly improved HbA1c levels. No hypoglycemic symptoms or severe hypoglycemia was reported in patients who completed the period of 12 weeks. CONCLUSIONS: We demonstrated the efficacy of repaglinide in patients with T2D and severe RI. In case that DPP-4 inhibitors are not enough to achieve targeted range of glycemic control, repaglinide is another good candidate.

Cellular localization and regional distribution of an angiotensin II-forming chymase in the heart.

The human heart is a target organ for the octapeptide hormone, angiotensin II (Ang II). Recent studies suggest that the human heart contains a dual pathway of Ang II formation in which the major Ang II-forming enzymes are angiotensin I-converting enzyme (ACE) and chymase. Human heart chymase has recently been purified and its cDNA and gene cloned. This cardiac serine proteinase is the most efficient and specific Ang II-forming enzyme described. To obtain insights into the cardiac sites of chymase-dependent Ang II formation, we examined the cellular localization and regional distribution of chymase in the human heart. Electron microscope immunocytochemistry using an anti-human chymase antibody showed the presence of chymase-like immunoreactivity in the cardiac interstitium and in cytosolic granules of mast cells, endothelial cells, and some mesenchymal interstitial cells. In the cardiac interstitium, chymase-like immunoreactivity is associated with the extracellular matrix. In situ hybridization studies further indicated that chymase mRNA is expressed in endothelial cells and in interstitial cells, including mast cells. Tissue chymase levels were determined by activity assays and by Western blot analyses. Chymase levels were approximately twofold higher in ventricles than in atria. There were no significant differences in chymase levels in ventricular tissues obtained from non-failing donor hearts, failing ischemic hearts, or hearts from patients with ischemic cardiomyopathy. These findings suggest that a major site of chymase-dependent Ang II formation in the heart is the interstitium and that cardiac mast cells, mesenchymal interstitial cells, and endothelial cells are the cellular sites of synthesis and storage of chymase. In the human heart, because ACE levels are highest in the atria and chymase levels are highest in ventricles, it is likely that the relative contribution of ACE and chymase to cardiac Ang II formation varies with the cardiac chamber. Such differences may lead to differential suppression of cardiac Ang II levels during chronic ACE inhibitor therapy in patients with congestive heart failure.

Angiotensin II antagonist prevents electrical remodeling in atrial fibrillation.

BACKGROUND: The blockade of angiotensin II (Ang II) formation has protective effects on cardiovascular tissue; however, the role of Ang II in atrial electrical remodeling is unknown. The purpose of this study was to investigate the effects of candesartan and captopril on atrial electrical remodeling. METHODS AND RESULTS: In 24 dogs, the atrial effective refractory period (AERP) was measured before, during, and after rapid atrial pacing. Rapid atrial pacing at 800 bpm was maintained for 180 minutes. The infusion of saline (n=8), candesartan (n=5), captopril (n=6), or Ang II (n=5) was initiated 30 minutes before rapid pacing and continued throughout the study. In the saline group, AERP was significantly shortened during rapid atrial pacing (from 149+/-11 to 132+/-16 ms, P<0.01). There was no significant difference in AERP shortening between the saline group and the Ang II group. However, in the candesartan and captopril groups, shortening of the AERP after rapid pacing was completely inhibited (from 142+/-9 to 147+/-12 ms with candesartan, from 153+/-15 to 153+/-14 ms with captopril, P=NS). Although rate adaptation of the AERP was lost in the saline group, this phenomenon was preserved in the candesartan and captopril groups. CONCLUSIONS: The inhibition of endogenous Ang II prevented AERP shortening during rapid atrial pacing. These results indicate for the first time that Ang II may be involved in the mechanism of atrial electrical remodeling and that the blockade of Ang II may lead to the better therapeutic management of human atrial fibrillation.

Overexpression of the human angiotensin II type 1 receptor in the rat heart augments load induced cardiac hypertrophy.

Angiotensin II is known to stimulate cardiac hypertrophy and contractility. Most angiotensin II effects are mediated via membrane bound AT1 receptors. However, the role of myocardial AT1 receptors in cardiac hypertrophy and contractility is still rarely defined. To address the hypothesis that increased myocardial AT1 receptor density causes cardiac hypertrophy apart from high blood pressure we developed a transgenic rat model which expresses the human AT1 receptor under the control of the alpha-myosin heavy-chain promoter specifically in the myocardium. Expression was identified and quantified by northern blot analysis and radioligand binding assays, demonstrating overexpression of angiotensin II receptors in the transgenic rats up to 46 times the amount seen in nontransgenic rats. Coupling of the human AT1 receptor to rat G proteins and signal transduction cascade was verified by sensitivity to GTP-gamma-S and increased sensitivity of intracellular Ca2+ [Ca2+]i to angiotensin II in fluo-3 loaded transgenic cardiomyocytes. Transgenic rats exhibited normal cardiac growth and function under baseline conditions. Pronounced hypertrophic growth and contractile responses to angiotensin II, however, were noted in transgenic rats challenged by volume and pressure overload. In summary, we generated a new transgenic rat model that exhibits an upregulated myocardial AT1 receptor density and demonstrates augmented cardiac hypertrophy and contractile response to angiotensin II after volume and pressure overload, but not under baseline conditions.

Antihypertensive and volume-depleting effects of mild exercise on essential hypertension.

After a general clinical observation period of over 4 weeks, 20 essential hypertensive subjects (Japanese) were randomly divided into two groups. One group (n = 10; 4 men and 6 women; 51.4 +/- 2.8 years of age) agreed to physical training using bicycle ergometer exercise with the intensity at blood lactate threshold for 60 minutes three times a week for 10 weeks, while the other group (n = 10; 4 men and 6 women; 51.0 +/- 2.9 years of age) did no particular physical training and was followed once a week as the control. Changes in blood pressure, hemodynamics, and humoral factors of the exercised group were compared with values in the controls. The following significant changes were found only in the exercised group. Blood pressure was significantly (p less than 0.01) reduced. Whole blood and plasma volume indices were significantly reduced (p less than 0.05, p less than 0.01, respectively). The change in ratio of serum sodium to potassium positively correlated with the change in systolic blood pressure (r = 0.76, p less than 0.02). Plasma norepinephrine concentrations both at rest and at the workload of blood lactate threshold during graded exercise tests were significantly reduced (p less than 0.05, p less than 0.02 respectively) after 10 weeks of exercise training. The change in the resting level of plasma norepinephrine positively correlated with that in the mean blood pressure. No such changes were observed in the control group. In both groups, body weight and urinary sodium excretion showed no statistically significant changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II receptors in normal and failing human hearts.

To demonstrate the existence and help clarify the function of angiotensin II (Ang II) receptors in the human heart, we characterized the cardiac Ang II receptor and examined the levels and distribution of ventricular Ang II receptors in normal (n = 6) and failing (n = 14) hearts. Ang II receptors were characterized using the Ang II receptor agonist [125I]Ang II. Cardiac [125I]Ang II-binding sites were of high affinity (Kd, approximately 1 nmol/L) and low capacity (Bmax, approximately 3 fmol/mg membrane protein) and were pharmacologically specific [IC50 values for Ang II, [Sar1,Ile8]Ang II, and Ang III were 1.2, 3.0, and 400 nmol/L, respectively; the inactive Ang II metabolite Ang-(1-5), at a concentration of 1 mumol/L, inhibited [125I]Ang II binding by less than 10%]. These characteristics of cardiac [125I]Ang II-binding sites are similar to those of previously characterized mammalian heart Ang II receptors. In normal adult donor hearts (n = 5), Ang II receptor density in the left ventricle [LV, 2.90 +/- 1.40 (+/- SE) fmol/mg] was similar to that in the right ventricle (RV, 3.82 +/- 1.10 fmol/mg). The ventricular Ang II receptor density in adult patients with idiopathic (LV, 1.77 +/- 0.35 fmol/mg; RV, 1.58 +/- 0.29 fmol/mg; n = 8) or dilated cardiomyopathy (LV, 2.00 +/- 0.58 fmol/mg; RV, 2.56 +/- 0.52 fmol/mg n = 5) was similar to that in the normal heart. Ventricular Ang II receptors, localized by autoradiography using the Ang II receptor antagonist [125I]-[Sar1,Ile8]Ang II, were consistently found in the myocardium, cardiac adrenergic nerves, and coronary vessels of normal and failing ventricles. In human ventricles Ang II receptor levels were not correlated with age. Because ventricular Ang II receptor density in a normal neonatal human heart and that in a heart from an adolescent patient with idiopathic cardiomyopathy were more than 10-fold and more than 5-fold higher, respectively, than in normal adult ventricles, we investigated whether postnatal changes occur in ventricular Ang II receptors in rats. In male and female rats ventricular Ang II receptor density was about 2-fold higher in 1-day-old rats compared to that in 10-day-old or peripubertal rats. These data suggest developmental regulation of ventricular Ang II receptors. Our findings suggest that direct and neural angiotensinergic inputs to the myocardium play a role in the regulation of cardiac function in man and that these inputs are preserved in the failing heart.

Increased chymase activity in internal thoracic artery of patients with hypercholesterolemia.

Apart from ACE, various angiotensin II (Ang II)-forming serine proteinases (eg, chymase, kallikrein, and cathepsin G) are known to exist in human tissues, but their clinical significance or the regulatory mechanisms that control their activities are not well established. A recent clinical study has shown that chymase activity was significantly increased in human atherosclerotic or aneurysmal aorta. The association between vascular Ang II-forming activities (AIIFAs) in the human internal thoracic artery (ITA) and various clinical parameters was studied with the use of ITAs obtained from 32 patients who underwent coronary artery bypass graft surgery. Total and ACE- and chymase-dependent AIIFAs in homogenates of ITAs were determined. Total AIIFA was 8.67+/-0.86 (nmol Ang II formed. min(-1). mg protein(-1) [U]), and approximately 95% of the activities were due to chymase. Serum total cholesterol level, but no other risk factors, significantly correlated with chymase- (r=0. 60, P<0.001) and ACE- (r=0.35, P<0.05) dependent AIIFAs, respectively. LDL cholesterol level was also correlated with chymase-dependent AIIFAs (r=0.47, P<0.05). Mast cells identified through the use of toluidine blue or immunohistochemical staining appeared in the adventitia but not in the intima or media of ITAs. Our results suggest that an increased plasma LDL cholesterol level may induce increased arterial chymase and ACE activity.

Differences in tissue angiotensin II-forming pathways by species and organs in vitro.

Angiotensin (Ang) II plays an important role in cardiovascular homeostasis, not only in the systemic circulation but also at the tissue level, and is involved in the remodeling of the heart and vasculature under pathological conditions. Although alternative Ang II-forming pathways are known to exist in various tissues, the details of such pathways remain unclear. The aim of this study was to examine tissue Ang II-forming activities and to identify the responsible enzyme in several organs (lung, heart, and aorta) in various species (human, hamster, rat, rabbit, dog, pig, and marmoset). Among the organs examined, the lung contained the highest Ang II-forming activity. The responsible enzyme for pulmonary Ang II formation was angiotensin I-converting enzyme (ACE) in all of the species except the human lung, in which a chymaselike enzyme was dominant. In the heart, the highest total Ang II-forming activity was observed in humans, and a chymaselike enzyme was dominant in all of the species except rabbit and pig. Aorta exhibited a relatively high total Ang II-forming activity, with a predominance of chymaselike activity in all of the species except rabbit and pig, in which ACE was dominant. Our results indicate that there were remarkable differences in Ang II-forming pathways among the species and organs we examined. To study the pathophysiological roles of ACE-independent Ang II formation, one should choose species and/or organs that have Ang II-forming pathways similar to those in humans.

Increased chymase-dependent angiotensin II formation in human atherosclerotic aorta.

Locally formed angiotensin II (Ang II) and mast cells may participate in the development of atherosclerosis. Chymase, which originates from mast cells, is the major Ang II-forming enzyme in the human heart and aorta in vitro. The aim of the present study was to investigate aortic Ang II-forming activity (AIIFA) and the histochemical localization of each Ang II-forming enzyme in the atheromatous human aorta. Specimens of normal (n=9), atherosclerotic (n=8), and aneurysmal (n=6) human aortas were obtained at autopsy or cardiovascular surgery from 23 subjects (16 men, 7 women). The total, angiotensin-converting enzyme (ACE)-dependent, and chymase-dependent AIIFAs in aortic specimens were determined. The histologic and cellular localization of chymase and ACE were determined by immunocytochemistry. Total AIIFA was significantly higher in atherosclerotic and aneurysmal lesions than in normal aortas. Most of AIIFA in the human aorta in vitro was chymase-dependent in both normal (82%) and atherosclerotic aortas (90%). Immunocytochemical staining of the corresponding aortic sections with antichymase, antitryptase or anti-ACE antibodies showed that chymase-positive mast cells were located in the tunica adventitia of normal and atheromatous aortas, whereas ACE-positive cells were localized in endothelial cells of normal aorta and in macrophages of atheromatous neointima. The density of chymase- and tryptase-positive mast cells in the atherosclerotic lesions was slightly but not significantly higher than that in the normal aortas, and the number of activated mast cells in the aneurysmal lesions (18%) was significantly higher than in atherosclerotic (5%) and normal (1%) aortas. Our results suggest that local Ang II formation is increased in atherosclerotic lesions and that chymase is primarily responsible for this increase. The histologic localization and potential roles of chymase in the development of atherosclerotic lesions appear to be different from those of ACE.

Effects of 1,3-chelation induced by cis-diamminedichloroplatinum(II) on the stability of DNA duplexes.

Several 1,3-intra-strand cross-linked decadeoxynucleotide duplexes, modified with cis-diamminedichloroplatinum(II) (cis-DDP), and their base substitution analogues at the complementary site to the intervening base of the coordination sites, were synthesized and measured for UV-melting profiles to determine melting temperature (Tm) values. The results indicated the thermal stability of the oligonucleotide duplexes containing Pt-induced 1,3-intra-strand cross-linking did not depend on the kind of intervening base of the coordination site but rather on its complementary base. These results may explain the mutagenicity of cis-DDP from a chemical aspect.

Substituted 3-(phenylsulfonyl)-1-phenylimidazolidine-2,4-dione derivatives as novel nonpeptide inhibitors of human heart chymase.

A series of 3-(phenylsulfonyl)-1-phenylimidazolidine-2,4-dione derivatives have been synthesized and evaluated for their ability to selectively inhibit human heart chymase. The structure-activity relationship studies on these compounds gave the following results. The 1-phenyl moiety participates in a hydrophobic interaction where an optimum size is required. At this position, 3,4-dimethylphenyl is the best moiety for inhibiting chymase and showed high selectivity compared with chymotrypsin and cathepsin G. A 3-phenylsulfonyl moiety substituted with hydrogen-bond acceptors such as nitrile and methoxycarbonyl enhances its activity. Molecular-modeling studies on the interaction of 3-[(4-chlorophenyl)sulfonyl]-1-(4-chlorophenyl)-imidazolidine-2,4-dione (29) with the active site of human heart chymase suggested that the 1-phenyl moiety interacts with the hydrophobic P1 pocket, the 3-phenylsulfonyl moiety resides in the S1'-S2' subsites, and the 4-carbonyl of the imidazolidine ring and sulfonyl group interact with the oxyanion hole and the His-45 side chain of chymase, respectively. The complex model is consistent with the structure-activity relationships.

Angiotensin-converting enzyme and heart chymase gene polymorphisms in hypertrophic cardiomyopathy.

We examined the insertion/deletion polymorphism in the angiotensin-converting enzyme gene and identified polymorphisms in the heart chymase gene to test the hypothesis that these angiotensin II-producing enzymes are associated with a monogenic cardiac disease (50 patients and 50 control subjects) as a model of cardiac hypertrophy. We found that the angiotensin-converting enzyme DD genotype was present more often in patients than in control subjects and identified a possible interaction with 1 of the chymase polymorphisms.

Chymase gene locus is not associated with myocardial infarction and is not linked to heart size or blood pressure.

The chymase gene is said to be important for the generation of angiotensin II in the heart and therefore is a candidate gene for heart disease. However, we were unable to find an association between allelic variants of the chymase gene and acute myocardial infarction or linkage between the chymase gene locus and heart size.

Dual pathway for angiotensin II formation in human internal mammary arteries.

1. Angiotensin converting enzyme (ACE) is thought to be the main enzyme to convert antiotensin I to the vasoactive angiotensin II. Recently, in the human heart, it was found that the majority of angiotensin II formation was due to another enzyme, identified as human heart chymase. In the human vasculature however, the predominance of either ACE or non-ACE conversion of angiotensin I remains unclear. 2. To study the effects of ACE- and chymase-inhibition on angiotensin II formation in human arteries, segments of internal mammary arteries were obtained from 37 patients who underwent coronary bypass surgery. 3. Organ bath experiments showed that 100 microM captopril inhibited slightly the response to angiotensin I (pD2 from 7.09+/-0.11-6.79+/-0.10, P<0.001), while 100 microM captopril nearly abolished the response to [pro10] angiotensin I, a selective substrate for ACE, and the maximum contraction was reduced from 83+/-19%-23+/-17% of the control response (P=0.01). A significant decrease of the pD2 of angiotensin I similar to captopril was observed in the presence of 50 microM chymostatin (pD2 from 7.36+/-0.13-6.99+/-0.15, P<0.039), without influencing the maximum response. In the presence of both inhibitors, effects were much more pronounced than either inhibitor alone, and a 300 times higher dose was needed to yield a significant contraction response to angiotensin I. 4 These results indicate the presence of an ACE and a non-ACE angiontensin II forming pathway in human internal mammary arteries.

Chymase-dependent angiotensin II forming systems in humans.

Recent studies have provided evidence that human cardiovascular tissues contain components of the renin angiotensin system: angiotensinogen, renin, angiotensin I converting enzyme (ACE), chymase, and angiotensin (Ang) II receptors. It is likely that locally produced Ang II plays an important role in cardiovascular homeostasis in autocrine and paracrine fashions and may also be involved in remodeling of the heart and vasculature in pathological conditions. In addition to ACE, a cardiac Ang II-forming serine proteinase (human heart chymase) has been identified in the left ventricle of the human heart. The different cellular and regional distribution of ACE and heart chymase in the heart as well as in blood vessels implies distinct pathophysiological roles of these two Ang II-forming enzymes. Several reports indicate that both ACE dependent and ACE independent Ang II formation appears to take place in hypoxic or ischemic heart or blood vessel in vivo and seems to be involved in their pathological changes. However, chymase dependent Ang II formation, chymostatin sensitive but aprotinin insensitive, does not explain all of ACE independent Ang II formation. Therefore, it has become quite important to clarify the detailed mechanisms of the tissue Ang II formation in humans and their contribution to the pathophysiological changes in cardiovascular diseases.

Decreased skeletal muscle capillary density is related to higher serum levels of low-density lipoprotein cholesterol and apolipoprotein B in men.

The relationships between skeletal muscle morphology, particularly muscle fiber capillary density, and serum lipid profiles were evaluated in 25 non-obese men aged 18 to 36 years (body mass index [BMI], 22.7 +/- 2.5 kg/m2; body fat, 13.6% +/- 4.0%, maximal oxygen uptake [VO2max], 46.2 < or = 6.3 mL/kg/min). Skeletal muscle samples were taken from the vastus lateralis using the needle-biopsy method. The fiber types (I, IIa, and IIx) and their percent distribution, the indices of capillary density, and the diffusion index expressed as the cross-sectional area occupied by one capillary were determined. Blood samples were drawn from the antecubital vein after a 12-hour fast. Based on Pearson's correlation analysis, the number of capillaries around type IIx fiber correlated inversely with the serum level of low-density lipoprotein cholesterol ([LDL-C] r = -.50, P < .05). The number of capillaries per fiber (cap/fiber ratio), number of capillaries per area (cap/mm2), and capillaries around each fiber type correlated inversely with the serum level of apolipoprotein B ([apo B] r = -.40 to -.54, P < .05 to .01). Further, the diffusion index for each fiber type correlated positively with LDL-C and apo B (r = .42 to .50, P < .05 to .01). Among 14 subjects in whom high-density lipoprotein cholesterol (HDL-C) subfractions were analyzed, a positive correlation was found between cap/mm2 and HDL2-C (r = .64, P < .05). Partial correlation analysis showed that these correlations either remain or improve after adjusting for age, VO2max, and body fatness. These results indicate that skeletal muscle capillary density and diffusion capacity are related to lipid and apolipoprotein concentrations for both type I and type II fibers.

Rapidly functional immobilization of immortalized human hepatocytes using cell adhesive GRGDS peptide-carrying cellulose microspheres.

With the development of biotechnology, hepatic support by a hybrid artificial liver (HAL) using hepatocytes has been given much attention. Because the availability of human livers is limited, we have established a tightly regulated immortal human hepatocyte cell line, NKNT-3, for developing HAL. Because high-density cell culture allows the compactness of the HAL device and its easy use under emergency circumstances, we have developed cell adhesive GRGDS peptide-containing cellulose microspheres (GRGDS/CMS). The GRGDS/CMS efficiently immobilized NKNT-3 cells within 24 h in a stirred suspension culture. Electron microscopic examinations demonstrated glycogen granules and well-developed endoplasmic reticulum and mitochondria in NKNT-3 cells attached to the GRGDS/CMS. The cells showed ammonia clearance activity, whereas HepG2-transformed human liver cells did not remove the loaded ammonia. An efficient adenoviral delivery of the lacZ reporter gene was performed in GRGDS/CMS-immobilized NKNT-3 cells. In this study we present rapid immobilization of NKNT-3 immortal human hepatocytes using cellulose microspheres carrying GRGDS peptides. These microspheres satisfied immediate preparation of NKNT-3 cells in sufficient quantity and of adequate quality.

Angiotensin I converting enzyme and chymase in cardiovascular tissues.

Recent studies have provided evidence that the human cardiovascular tissues contain components of the renin-angiotensin system: angiotensinogen, renin, angiotensin I converting enzyme (ACE), chymase and angiotensin II (Ang II) receptors. In addition to ACE, a cardiac Ang II forming serine proteinase, human heart chymase, has been identified in the human left ventricle. Unlike rat heart, only a minor (approximately 11%) component of Ang II forming activity in the human left ventricle was due to ACE, since the majority (approximately 80%) of activity was due to chymase. Human heart chymase has been purified to homogeneity and characterized. Recently, the cDNA and gene for this enzyme have been cloned. Biochemical characterization revealed that heart chymase is the most efficient and specific Ang II forming enzyme described thus far. The different cellular and regional distribution of ACE and heart chymase in the heart as well as in blood vessels implies distinct pathophysiological roles for these two Ang II forming enzymes. Several reports indicate that ACE-independent Ang II formation appears to take place in hypoxic or ischemic heart or blood vessel in vivo and to be involved in vascular remodeling after balloon injury. Therefore, it is very important to clarify the detailed mechanisms of the tissue Ang II formation in humans and its contribution to the pathophysiological changes in cardiovascular disease. In this review, we review the pathophysiological roles of the two main Ang II forming enzymes, ACE and chymase, in cardiovascular homeostasis.

Mechanism of the cardioprotective effect of inhibition of the renin-angiotensin system on ischemia/reperfusion-induced myocardial injury.

Inhibition of the renin-angiotensin system (RAS) has been shown to be beneficial in providing cardioprotective effects in humans, but the mechanism of these effects is not well understood. In this study, we examined the effects and mechanism of RAS inhibitors on ischemia/reperfusion (IR)-induced myocardial injury in rats. Rats were randomly divided into five groups and treated with vehicle (C), angiotensin converting enzyme inhibitor (ACE-I), angiotensin II type 1 receptor antagonist (AT1-A), angiotensin II type 2 receptor antagonist (AT2-A) or ACE-I plus bradykinin B2 antagonist. Ten minutes after administration, the left main coronary artery was ligated for 45 min, and then reperfused for 120 min. IR-induced cardiomyocyte apoptosis was assessed by terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay and confirmed by typical DNA laddering. Mitogen-activated protein kinase, extracellular signal-regulated protein kinase (ERK) and c-Jun NH2-terminal protein kinase (JNK) activity in the ischemic zone were measured by an in vitro kinase assay. The duration of ventricular tachycardia (VT) during ischemia was reduced by AT2-A and ACE-I, and increased by AT1-A and ACE-I+icatibant. ACE-I and AT2-A reduced apoptosis (by 54% and 53%) and infarct size (by 42% and 41%), while AT1-A increased apoptosis (by 86%) and infarct size (by 45%). These changes were negatively correlated with the change in ERK activity. The effects of ACE-I on apoptosis and infarct size were abolished by the coadministration of icatibant. Apoptosis was correlated with the occurrence of VT (r=0.837, p<0.001). These results suggest that both the accumulation of bradykinin and inhibition of AT2 receptor are cardioprotective against IR injury through the activation of ERK, but not JNK.

Activation of renal dopamine system by physical exercise.

Physical exercise is one of the life-style modifications used for lowering blood pressure. Except for diminished norepinephrine spill over, the mechanism by which physical exercise exerts its effects was not known. Based on our preliminary finding that the reduction of blood pressure was inversely correlated to the baseline plasma renin activity, we have consequently revealed that mild exercise reduces plasma volume and hence the cardiac index. In order to elucidate the mechanism, we have investigated all possible parameters relevant to plasma volume regulation. Among them, urinary free dopamine and urinary active kallikrein increased in the early stages (weeks 2-4) while atrio-natriuretic factor (week 4) and endogeneous ouabain-like substance (EOLS) consequently (weeks 7-10) decreased. Serum taurine increased and plasma norepinephrine decreased in the late stages. The conclusion reached is that mild exercise seems to first activate the renal dopamine and kallikrein systems and second trigger other mechanism, such as an increase in taurine and decreases in EOLS and norepinephrine.