Effect of estrogen on global myocardial ischemia-reperfusion injury in female rats

We investigated the effects of estrogen on global myocardial ischemia-reperfusion injury in rats that were ovariectomized (Ovx), sham-operated, or ovariectomized and then given 17beta-estradiol (E(2)beta) supplementation (Ovx+E(2)beta). Hearts were excised, cannulated, perfused with and then immersed in chilled (4 degrees C) cardioplegia solution for 30 min, and then retrogradely perfused with warm (37 degrees C), oxygenated Krebs-Henseleit bicarbonate buffer for 120 min. The coronary flow rate, first derivative of left ventricular pressure, and nitrite production were all significantly lower in Ovx than in sham-operated or Ovx+E(2)beta hearts. However, coronary flow rates or nitrate production were not consistently different throughout the entire reperfusion period. Ca(2+) accumulated more in Ovx rat hearts than in sham-operated or Ovx+E(2)beta hearts, and mitochondrial respiratory function was lower in Ovx hearts than in hearts from the other two groups. Marked interstitial edema and contraction bands were seen in hematoxylin-eosin-stained sections of Ovx rat hearts but not in hearts from either of the other groups. Hematoxylin-basic fuchsin-picric acid-stained sections revealed fewer viable myocytes in hearts from the Ovx group than from the sham or Ovx+E(2)beta group. Transmission electron microscopy demonstrated more severely damaged mitochondria and ultrastructural damage to myocytes in Ovx rat hearts. Our results indicate that estrogen plays a cardioprotective role in global myocardial ischemia-reperfusion injury in female rats.     

Tetrahydrobiopterin improves vascular endothelial function in ovariectomized rats

The goal of the present study is to investigate the role of tetrahydrobiopterin (BH4) in the vascular response in ovariectomized rats. Rats were randomly assigned to two groups: (1) sham group: sham-operated female rats, and (2) Ovx group: rats were ovariectomized. Our results have shown that the plasma 17 beta-estradiol levels in the Ovx group at the end of the experiment were significantly lower than in the sham group. Vasoreactivity assessed with intact aortic rings indicated that the phenylephrine-induced vasocontractile response to aortic rings from the Ovx group was greater than that of the sham group. In contrast, the vasodilator responses to acetylcholine and L-arginine (L-Arg) in the sham group were significantly greater than in the Ovx group. Differences in vasoreactivity in denuded aorta between the two groups were not noted. Moreover, exogenous BH4 significantly restored L-Arg-induced vasodilator responses in the Ovx group. However, this improvement effect was not found in the sham group. In addition, there were significant increases in superoxide anion production in aortic tissue and significant decreases in plasma nitric oxide levels in the Ovx group. Furthermore, BH4 contents in the aorta in the Ovx group were significantly decreased compared with the sham group. In conclusion, the present study demonstrates that the impairment of vascular reactivity was found in the ovariectomized rats. The possible mechanism of this defect may have resulted from the deficiency of available BH4. Thus, this study may provide a novel therapeutic strategy for the treatment of postmenopausal cardiovascular disorders.     

Lipid peroxidation in ovariectomized and pinealectomized rats: the effects of estradiol and progesterone supplementation

In the present study, we investigated the effect of estradiol and progesterone supplementation on oxidant and antioxidant parameters of renal tissue in ovariectomized and pinealectomized rats. The study was carried out on 36 adult, Sprague-Dawley strain female rats, 6 months of age and weighing 200-250 g. The rats were divided into six groups, each group included six rats: Group 1: Sham-ovariectomized (Sham-Ovx); Group 2: Ovariectomized (Ovx); Group 3: Ovx and estradiol (E) and progesterone (P) supplemented (Ovx+E-P); Group 4: Ovariectomized and sham pinealectomy (Ovx+sham Pnx); Group 5: Ovariectomized+Pinealectomized (Ovx+Pnx); Group 6: Ovariectomized+Pinealectomized+Hormone Supplemented group (Ovx+Pnx+E-P). The levels of malondialdehyde (MDA), reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) were analysed in renal tissues of rats. The highest and the lowest levels of MDA were determined in Groups 5 and 1 respectively (p < 0.001). However, GSH and GSH-Px levels demonstrated statistically important decreases in groups 2, 4, 5 (p < 0.001). The findings of this study demonstrate that ovariectomy leads to oxidative damage in renal tissue. Pinealectomy in addition to ovariectomy greatly increases the oxidative damage. However, female sex hormones supplementations to the Ovx and/or Ovx+Pnx rats protected against lipid peroxidation by activating the antioxidant system.     

Ingestion of raffinose promotes calcium absorption in the large intestine of rats

We examined the effects of feeding raffinose on intestinal calcium absorption in ovariectomized rats by two separate experiments. In experiment 1, female Sprague-Dawley rats (6 wk old) were divided into two groups: sham operation and ovariectomy, and fed diets with or without raffinose (30 g/kg diet) for 4 wk. In experiment 2, ovariectomized rats with cecocolonectomy or transsection and reanastomosis (sham) were divided into two groups as in experiment 1 and fed the same diets for 3 wk. In experiment 1, calcium absorption was lower in the ovariectomized rats than in the sham rats but calcium absorption in rats fed the raffinose diet was higher than that in rats fed the raffinose-free diet. In experiment 2, increased calcium absorption in the raffinose group was abolished by cecocolonectomy. The impaired absorption in ovariectomized rats was restored by feeding raffinose. The large intestine is involved in the beneficial effects of raffinose.     

Cardioprotection in female rats subjected to chronic volume overload: synergistic interaction of estrogen and phytoestrogens

Intact female rats fed a high-phytoestrogen diet are protected against adverse left ventricular (LV) remodeling induced by chronic volume overload. We hypothesized that both phytoestrogens and ovarian hormones, particularly estrogen, are necessary for this dietary-induced cardioprotection. To test this hypothesis, eight groups of female rats were studied; rats were fed either a high-phytoestrogen (+phyto) or phytoestrogen-free diet. Groups included sham-operated rats, intact rats with fistula (Fist), ovariectomized rats with fistula (Fist-OX), and Fist-OX rats treated with estrogen (EST). Myocardial function and remodeling were assessed after 8 wk of volume overload using a blood-perfused isolated heart apparatus. Fist-OX rats developed significant ventricular dilatation and increased compliance vs. intact Fist rats, which were associated with a significant decrease in contractility. Estrogen treatment prevented pulmonary edema and attenuated LV hypertrophy and dilatation but did not maintain contractility. However, dietary phytoestrogens completely prevented LV dilatation in both the Fist+phyto and Fist-OX+EST+phyto groups but had no effect on LV remodeling in the Fist-OX+phyto group. Contractility was significantly greater in the estrogen-treated rats fed the phytoestrogen diet than in those treated with estrogen alone. Dietary phytoestrogens did not affect LV or uterine mass, serum estrogen, LV estrogen receptor expression, or cardiac function in sham animals. These data indicate that estrogen is not solely responsible for the cardioprotection exhibited by intact females and that phytoestrogens can work synergistically with ovarian hormones to attenuate ventricular remodeling induced by chronic volume overload in female rats.     

The influence of estradiol and progesterone and melatonin supplementation on TNF-alpha levels in ovariectomized and pinealectomized rats

The aim of this study was to investigate the effect of estradiol and progesterone and melatonin supplementation on TNF-alpha levels in ovariectomized and pinealectomized rats. The study was carried out on 42 adult, Spraque-Dawley strain female rats aged 6 months and weighing 200-250 grams. The rats were divided into 6 groups, each group contained 7 rats. Group 1: Sham-ovariectomized (Sham-Ovx), Group 2: Ovariectomized (Ovx), Group 3: Ovx and estradiol (E) and progesterone (P) supplemented (Ovx+E-P) group, Group 4: Ovx+E-P+Melatonin (M) supplemented group, Group 5: Ovx Pinealectomized (Pnx) group, Group 6: Ovx - Pnx+E-P supplemented group. Serum TNF-alpha levels were determined after 4 weeks application period. Group 6 (Ovx-Pnx+E-P) has the highest serum TNF-alpha compared with other groups while group 2 (ovariectomized), has the lowest levels (P<0.001). Group 5 was higher than groups 1, 2, 3 and 4 (P <0.001). The results of the study show that ovariectomy reduces the serum level of TNF-alpha, but estradiol and progesterone application prevents this reduction in ovariectomized rats. However, pinealectomy intensifies the increases in TNF-alpha levels in ovariectomized and estradiol and progesterone supplemented rats, whereas melatonin reduces TNF-alpha levels in ovariectomized rats.     

Hyperbaric oxygen preconditioning alleviates myocardial ischemic injury in rats

It has been shown that after ischemia-reperfusion, application of hyperbaric oxygen (HBO) reduces cardiac injury. In this study we tested the hypothesis that HBO preconditioning reduces injury to the ischemic myocardium. One hundred and eight adult male Sprague-Dawley rats (250-280 g) were randomly divided into four groups: normoxia + sham surgery (CS), normoxia + permanent occlusion of the left anterior descending (LAD) coronary artery (CMI), HBO preconditioning + sham surgery (HS), and HBO preconditioning + permanent LAD occlusion (HMI). Rats receiving HBO preconditioning were intermittently exposed to 100% O(2) at 2.5 atmosphere absolute (ATA) for 60 min, twice daily for 2 days followed by 12 hrs of recovery in room air prior to the myocardial ischemic insult induced by LAD ligation. Rats in the normoxia group were time-matched with the HBO group and maintained under normoxic conditions prior to LAD occlusion. At 3 and 7 days after LAD occlusion, heart function parameters were measured by inserting a catheter into the left ventricle, infarct size was calculated using the method of TTC staining, myocardial capillary density was determined by immunohistochemical staining with a monoclonal anti-CD(31)/PECAM-1 antibody, and VEGF protein level was determined by Western blot analysis. At 3 days after LAD ligation, the infarct size of the HMI group was significantly smaller than that of the CMI group (26 +/- 2.5% vs. 38 +/- 3%, P < 0.05). The heart function parameters including left ventricular systolic pressure (LVSP), +dP/dt(max) and -dP/dt(max) were significantly improved in the HMI group compared to the CMI group at 3 and 7 days after LAD occlusion. Capillary density and VEGF protein levels were significantly increased in the ischemic myocardium pre-exposed to HBO. We conclude that HBO preconditioning alleviates myocardial ischemia in rat model.     

Estrogens influence cholecystokinin stimulated pancreatic amylase release and acinar cell membrane cholecystokinin receptors in rat.

This study examines the influence of ovariectomy and administration of a pharmacologic dose of estradiol on amylase release from isolated-dispersed rat pancreatic acini and cholecystokinin receptors on rat acinar cell membranes. Rats were sham ovariectomized (intact) or ovariectomized (Ovx) and 21 day timed release pellets containing either estradiol (2.5 mg) or vehicle, were implanted subcutaneously. Eighteen days later, pancreatic acini were isolated from rats by collagenase digestion and differential centrifugation. Total cellular amylase, basal and cholecystokinin octapeptide (CCK8) stimulated amylase release and CCK membrane receptors were measured. Acini isolated from estradiol treated Ovx rats had significantly greater total cellular amylase, compared to acini isolated from either intact or Ovx rats. The amplitude of both total stimulated amylase release and percent total stimulated amylase release were significantly greater for acini isolated from vehicle treated Ovx rats, than acini isolated from either intact or estradiol treated Ovx rats. The magnitude of percent total amylase release of acini isolated from estradiol treated Ovx rats was significantly lower than that of acini isolated from intact rats. Cholecystokinin receptor concentration was significantly greater on membranes prepared from vehicle treated Ovx rats, compared to membranes prepared from either intact or estradiol treated Ovx rats. These data indicate that ovariectomy is associated with increased responsiveness of pancreatic acini to CCK stimulation, while chronic estradiol treatment of ovariectomized rats is associated with increased total cellular amylase and decreased acinar cell responsiveness to CCK8. Estrogen mediated alterations in acinar cell amylase content and amylase release may play a role in estrogen related pancreatitis.     

Organic Gallium Treatment Improves Osteoporotic Fracture Healing Through Affecting the OPG/RANKL Ratio and Expression of Serum Inflammatory Cytokines in Ovariectomized Rats

This study aimed to investigate the impact of organic gallium (OG) on osteoporotic fracture healing in ovariectomized female Sprague-Dawley rats, as well as study the mechanisms of OG on osteoporotic fracture healing. Forty-five female Sprague-Dawley rats were divided into three groups: sham operation group (Sxas control group), ovariectomized group (Ovx), and Ovx treated with OG group (Ovx + OG). Rat femoral fractures were studied using a standardized fracture-healing model utilizing bone fixation with an intramedullary pin. Six weeks later, analyses of micro-CT, histomorphometric, RNA extraction, RT-qPCR, and serum were performed following sacrifice of all mice. In comparison with Ovx group, OG can significantly increase bone volume (BV), tissue volume (TV), BV/TV radio, bone strength, callus bony area, and as similar to BMP-2 expression. OG treatment elevated OPG messenger RNA (mRNA) and inhibited RANKL mRNA, and showed an effect on OPG/RANKL ratio. OG treatment can inhibit the expression of TNF-α and IL-6. In conclusion, current study results indicate that organic OG can positively affect the OPG/RANKL ratio and inhibit the expression of serum inflammatory cytokines; thus, it can improve osteoporotic fracture healing.     

Gender differences in the cardiac response to dietary conjugated linoleic acid isomers

The present study was undertaken to assess the heart function, by the in vivo catheterization technique, of healthy male and female Sprague-Dawley rats fed different conjugated linoleic acid (CLA) isomers, (cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12)) individually and in combination (50:50 mix as triglyceride or fatty acids) from 4 to 20 weeks of age. Whereas the triglyceride form of the CLA isomer mix lowered the heart rate, the rate of contraction (+dP/dt) and rate of relaxation (-dP/dt), systolic and diastolic pressures, mean arterial pressure, and the left ventricular systolic pressure were higher in male rats as compared with all the other dietary groups. In contrast, there were no significant effects in the cardiac function of the female rats in response to the CLA isomer mix in triglyceride form. Whereas the heart rate, +dP/dt, and left ventricular systolic pressure were lower in male rats fed the t10,c12 CLA isomer alone, the heart rate of the female rats was higher, but the systolic pressure, +dP/dt, and mean arterial pressure were lower compared with the control group. Also, the left ventricular end-diastolic pressure was specifically higher in the female rats in response to free fatty acids-containing CLA mix. Furthermore, an additive effect of the free fatty acids-containing CLA mix was seen in the +dP/dt and -dP/dt of female rats compared with the control group. These results indicate that CLA isomers exert differential effects on heart function and suggest the need for a complete evaluation of the benefits, interactions, and potential side effects of each isomer.     

Cardioprotective effects of rosiglitazone are associated with selective overexpression of type 2 angiotensin receptors and inhibition of p42/44 MAPK

Current evidence points to renin-angiotensin system as a key mediator in ischemia-reperfusion injury. Rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand, has recently been shown to confer cardioprotection against ischemia-reperfusion in animal models. We sought to examine the expression of ANG II receptors during PPAR-gamma-mediated cardioprotection. Male Sprague-Dawley rats (nondiabetic) were fed either regular rat chow (control diet group, n = 9) or rosiglitazone-rich diet (rosiglitazone-rich diet group, n = 9) and were subjected to 1 h of myocardial ischemia followed by 1 h of reperfusion. A third group of rats had only thoracotomy and pericardiotomy and served as a sham control group (n = 9). Hemodynamics, infarct size, and expression of ANG II type 1 and type 2 receptors (AT1 and AT2) were measured in all groups. There was a 58% reduction of infarct size in the rosiglitazone-rich diet group (P < 0.01 vs. control diet group). Increased myocardial expression of AT(1) receptors in the ischemic-reperfused myocardium was attenuated in the rosiglitazone-rich diet group (P < 0.05 vs. control diet group). Importantly, myocardial AT2 mRNA and protein expression were significantly increased (by >100-fold) in the rosiglitazone-rich diet group (P < 0.05). These changes were accompanied by inhibition of p42/44 MAPK in the rosiglitazone-rich diet group, while the Akt1 expression, believed to mediate insulin sensitization, remained similar in all three groups. The cardioprotective effects of rosiglitazone against myocardial ischemia-reperfusion injury are independent of its insulin-sensitizing properties and are associated with significant overexpression of AT2 receptors along with inhibition of p42/44 MAPK.     

雌激素对去卵巢大鼠离体心脏缺血／再灌注损伤的保护作用

目的：探讨雌激素对去卵巢大鼠离体心脏缺血／再灌注损伤的保护作用。方法：成年SD雌鼠,随机分为假手术组（Sham）,双侧卵巢切除组（Ovx）和双侧卵巢切除后补充17β-雌二醇组（Ovx＋E2）。各组离体心脏再随机分为不同时间的缺血再灌注亚组。测量的指标包括冠脉流出液中LDH及CK含量、心室肌细胞存活率及产率、基础状态和异丙肾上腺素（ISO）刺激状态下收缩幅度。结果：30min缺血及其各复灌纽均显著增加冠脉流出液中LDH、CK的释放量。Ovx组LDH、CK漏出在30min缺血及再灌注条件下,显著高于正常灌注组,而Ovx＋E2组可减轻心肌损伤,减少LDH、CK的释放。10min和20min缺血对心肌细胞存活率、产率及冠脉流出液中LDH、CK含量影响均不明显。Sham、Ovx、Ovx＋E2各组心肌细胞基础收缩幅度在正常和10minⅠ＋30minR灌注条件下无显著差异。Ovx显著增加其他各组心肌细胞基础收缩和ISO刺激收缩幅度,Ovx＋E2可使其降至Sham水平。结论：雌激素对去卵巢大鼠心肌缺血／再灌注损伤具有保护作用。     

The differential effects of alpha 2-adrenergic stimulation on the myocardium and coronary vessels in the isolated rat heart

The differential effects of alpha 2-adrenoceptor stimulation on myocardial contractility and coronary circulation were examined in the isolated perfused rat heart. We studied 20 Sprague-Dawley rats of similar age (26-28 weeks) and body weight (500-550 gm). Myocardial contractility (LV +dp/dt and developed pressure, LVP) and coronary flow resistance (CFR) were tested in the isolated isovolumic hearts using Langendorff preparation at a constant perfusion rate (2.5 ml/min/100 g BW) of Krebs-Henseleit bicarbonate solution. Group I (N-7) received B-HT 920 (specific alpha 2-adrenergic agonist, 0.6 to 58 micrograms/min), Group II (N-7) received B-HT 920+Yohimbine (300 nM in the perfusate). Group III (N-6) received vehicle only. Baseline LVP, LV +dP/dt and CFR were not significantly different among the 3 groups. During drug or vehicle administration, LVP and LV +dP/dt remained unchanged in all the groups. Coronary flow resistance increased in a dose-response fashion with a maximum increase of 22.7 +/- 3.6 (SE) mmHg/ml/min/g LV in Group I, and 10.5 +/- 2.0 mmHg/ml/min/g LV in Group II (p less than 0.02). We conclude that in the Sprague-Dawley rat heart, the physiologic effects of alpha 2-adrenoceptors are predominant in the coronary circulation but not in the myocardium itself possibly because of absence of post-synaptic alpha 2-adrenergic receptors in the rat myocardium.     

Effects of exercise on insulin distribution and action in testosterone-treated oophorectomized female rats.

Administration of testosterone (T) to oophorectomized (Ovx) female rats is followed by severe insulin resistance, localized to postreceptor cellular events in the muscle. In this study, intervention by exercise was introduced to examine whether circulatory adaptations are involved in insulin resistance. Two groups of Ovx rats were studied: one group was given T (Ovx+T); another group had free access to running wheels (Ovx+T+Ex). In addition, one control group (sham operated) was studied. Insulin sensitivity was measured with the euglycemic hyperinsulinemic clamp technique (submaximal) for 150 min. Muscle interstitial glucose and insulin concentrations were measured by microdialysis. The measurements showed that, in Ovx+T rats, the onset of insulin action was significantly (P < 0.05) slower during the first 95 min of the clamp compared with that in Ovx+T+Ex and controls. Muscle interstitial concentrations of insulin but not glucose were lower in both Ovx+T and Ovx+T+Ex rats than in controls throughout the clamp. It was concluded that physical exercise prevented the slow onset of insulin action in Ovx+T rats without changing the distribution time of muscle interstitial insulin. The results indicate that hyperandrogenicity is characterized by delayed muscle insulin action. Physical exercise reverses these defects without any beneficial effect on muscle interstitial insulin concentrations.     

STAT-3 activation is necessary for ischemic preconditioning in hypertrophied myocardium

The JAK-STAT pathway is activated in the early and late phases of ischemic preconditioning (IPC) in normal myocardium. The role of this pathway and the efficacy of IPC in hypertrophied hearts remain largely unknown. We hypothesized that phosphorylated STAT-3 (pSTAT-3) is necessary for effective IPC in pressure-overload hypertrophy. Male Sprague-Dawley rats 8 wk after thoracic aortic constriction (TAC) or sham operation underwent echocardiography and Langendorff perfusion. Randomized hearts were subjected to 30 min of global ischemia and 120 min of reperfusion with or without IPC in the presence or absence of the JAK-2 inhibitor AG-490 (AG). Functional recovery and STAT activation were assessed. TAC rats had a 31% increase in left ventricular mass (1,347 +/- 58 vs. 1,028 +/- 43 mg, TAC vs. sham, P < 0.001), increased anterior and posterior wall thickness but no difference in ejection fraction compared with sham-operated rats. In TAC, IPC improved end-reperfusion maximum first derivative of developed pressure (+dP/dt(max); 4,648 +/- 309 vs. 2,737 +/- 343 mmHg/s, IPC vs. non-IPC, P < 0.05) and minimum -dP/dt (-dP/dt(min); -2,239 +/- 205 vs. -1,215 +/- 149 mmHg/s, IPC vs. non-IPC, P < 0.05). IPC increased nuclear pSTAT-1 and pSTAT-3 in sham-operated rats but only pSTAT-3 in TAC. AG in TAC significantly attenuated +dP/dt(max) (4,648 +/- 309 vs. 3,241 +/- 420 mmHg/s, IPC vs. IPC + AG, P < 0.05) and -dP/dt(min) (-2,239 +/- 205 vs. -1,323 +/- 85 mmHg/s, IPC vs. IPC + AG, P < 0.05) and decreased only nuclear pSTAT-3. In myocardial hypertrophy, JAK-STAT signaling is important in IPC and exhibits a pattern of STAT activation distinct from nonhypertrophied myocardium. Limiting STAT-3 activation attenuates the efficacy of IPC in hypertrophy.     

Lipid peroxidation in liver tissue of ovariectomized and pinealectomized rats: effect of estradiol and progesterone supplementation

The present study aimed to determine the effect of estradiol-progesterone supplementation and pinealectomy on lipid peroxidation of liver tissue in ovariectomized rats. The study was carried out on 36 adult Sprague-Dawley female rats, which weighed 200-250 g. The rats were divided into 6 groups: Group 1: Sham Ovariectomy (Sham-Ovx), Group 2: Ovariectomy (Ovx), Group 3: Ovx + Estradiol-Progesterone supplementation (Ovx + H), Group 4: Sham Pinealectomy and Ovx (Sham Pnx -Ovx), Group 5: Ovx -Pnx, Group 6: Ovx -Pnx + H. Malondialdehyde (MDA), reduced form of glutathione (GSH) and glutathione peroxidase (GSH-Px) levels were determined in liver tissue of rats. The highest MDA levels and the lowest GSH-Px levels were determined in the ovariectomized-pinealectomized group, whereas the lowest MDA was in the Sham-Ovx group, and the highest GSH-Px levels were found in the Sham-Ovx and Ovx + Hormone supplemented group. Furthermore, the highest GSH levels were in group 1 and lowest levels were in group 5. The findings of this study demonstrate that ovariectomy led to lipid peroxidation in liver tissues of rats. Pinealectomy in addition to ovariectomy, increases lipid peroxidation, but, estradiol and progesterone supplementations to the ovariectomized-pinealectomized rats protect against lipid peroxidation to a significant extent.     

Impact of estrogen replacement on ventricular myocyte contractile function and protein kinase B/Akt activation

Women with functional ovaries have a lower cardiovascular risk than men and postmenopausal women. However, estrogen replacement therapy remains controversial. This study examined the effect of ovarian hormone deficiency and estrogen replacement on ventricular myocyte contractile function and PKB/Akt activation. Nulliparous female rats were subjected to bilateral ovariectomy (Ovx) or sham operation (sham). A subgroup of Ovx rats received estrogen (E(2)) replacement (40 microg. kg(-1). day(-1)) for 8 weeks. Mechanical and intracellular Ca(2+) properties were evaluated including peak shortening (PS), time to PS (TPS), time to 90% relengthening (TR(90)), maximal velocity of shortening/relengthening (+/-dL/dt), fura 2 fluorescence intensity (FFI), and decay rate. Levels of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a), phospholamban (PLB), and Akt were assessed by Western blot. Ovx promoted body weight gain associated with reduced serum E(2) and uterine weight, all of which were abolished by E(2). Ovx depressed PS and +/-dL/dt, prolonged TPS, TR(90), and decay rate, and enhanced resting FFI, all of which, with the exception of TPS, were restored by E(2). Ovx did not alter the levels of SERCA2a, PLB, and total Akt, but significantly reduced Akt activation [phosphorylated Akt (pAkt)], pAkt/Akt, and the SERCA2a-to-PLB ratio. These alterations in protein expression were restored by E(2). E(2) enhanced PS and +dL/dt in vitro, which was abolished by the E(2) receptor antagonist ICI-182780. Ovx reduced myocyte Ca(2+) responsiveness and lessened stimulating frequency-induced decline in PS, both ablated by E(2). These data suggest that mechanical and protein functions of ventricular myocytes are directly regulated by E(2).     

Effect of dietary calcium: Phosphorus ratio on bone mineralization and intestinal calcium absorption in ovariectomized rats

We investigated the effect of dietary calcium:phosphorus (Ca:P) ratio on bone mineralization and intestinal Ca absorption in ovariectomized (OVX) rat models of osteoporosis and sham-operated rats. Thirty 12-wk-old female Wistar rats were divided into three groups of OVX rats and three groups of sham rats. Thirty days after the adaptation period, OVX rats and sham rats were fed a diet formulated Ca:P, 1:0.5, 1:1 or 1:2 (each diet containing 0.5% Ca), respectively for 42 d. In both sham and OVX rats, serum osteocalcin, a marker of bone turnover, was increased by decreasing Ca:P ratio (1:2). In contrast, rats fed the Ca:P = 1:0.5 diet (dietary P restriction) suppressed the increased serum parathyroid hormone, osteocalcin and urinary deoxypyridinoline, and increased Ca absorption in both sham and OVX rats compared to the Ca:P = 1:1 and 1:2 diets. Especially, in OVX rats, the decreased bone mineral density of the fifth lumbar was also suppressed when rats were fed the Ca:P = 1:0.5 diet. These results indicated that the elevation of dietary Ca:P ratio may inhibit bone loss and increase intestinal Ca absorption in OVX rats.     

Food restriction suppresses muscle growth and augments osteopenia in ovariectomized rats.

We examined effects of 4 wk of food restriction on ovariectomy-related changes in muscle, bone, and plasma insulin-like growth factor I (IGF-I). Female Sprague-Dawley rats (7 mo old) were assigned to freely eating groups: sham-operated (Sham), ovariectomized (Ovx-AL), and estrogen (estradiol)-replaced Ovx (Ovx+E(2)). Ovx rats were also pair fed with Sham (Ovx-PF) or weight matched with Sham by food restriction (Ovx-FR). Ovx-AL and Ovx-PF rats had similar estrogen status and body weight; therefore, the groups were combined (group: Ovx). After treatment, body weight was approximately 10% greater in Ovx than in Sham rats (P < 0.05), and muscle weight-to-body weight ratios were comparable among all groups. Bone mineral contents of whole tibiae in Ovx-FR and Ovx were approximately 15% (P < 0.05) and approximately 6% lower than in Sham rats (P < 0.05), respectively. Plasma IGF-I was approximately 30% higher in Ovx than in Sham (P < 0.05) but was similar between Sham and Ovx-FR. IGF-I was highly correlated with body weight and muscle mass. Within non-estrogen-replaced Ovx rats, IGF-I explained approximately 19% of variance in bone mineral content after accounting for variance attributable to body weight. Findings suggest that estrogen acts indirectly on skeletal muscle and bone in rats through regulation of body growth by factors such as IGF-I.     

Validation of echocardiographic methods for assessing left ventricular dysfunction in rats with myocardial infarction

The rat infarct model is widely used in heart failure research, but few echocardiographic indexes of left ventricular (LV) function are validated in this model. Accordingly, the objective of this study was to validate a 13-segment LV wall motion score index (WMSI) and the myocardial performance index (MPI) in infarcted rats. Twenty-nine male Wistar rats underwent left coronary artery ligation or sham operation and were evaluated with two-dimensional and Doppler flow echocardiography 8 wk later. After echocardiography, invasive indexes were obtained using a high-fidelity catheter. WMSI and MPI were correlated with the invasive and noninvasive measurements of LV function. WMSI and MPI significantly correlated directly with end-diastolic pressure (r=0.72 and 0.42 for WMSI and MPI, respectively) and the time constant of isovolumic relaxation (r=0.68 and 0.48) and inversely with peak rate of rise of LV pressure (+dP/dt; r=-0.68 and -0.50), peak rate of decline in LV pressure (r=-0.57 and -0.44), LV developed pressure (r=-0.58 and -0.42), area fractional shortening (r=-0.85 and -0.53), and cardiac index (r=-0.74 and -0.74). Stepwise linear regression analyses revealed that LV end-diastolic pressure, +dP/dt, area fractional shortening, and cardiac index were independent determinants of WMSI (r=0.994) and that cardiac index and +dP/dt were independent determinants of MPI (r=0.781). We conclude that the 13-segment WMSI and MPI are reproducible and correlate strongly with established echocardiographic and invasive indexes of systolic and diastolic function. These findings support the use of WMSI and MPI as indexes of global LV function in the rat infarction model of heart failure.