The role of estrogen receptor subtypes in ameliorating hepatic injury following trauma-hemorrhage

BACKGROUND/AIMS: The aim of this study was to determine which of the estrogen receptor (ER) subtypes plays a predominant role in ameliorating hepatic damage following trauma-hemorrhage. METHODS: Adult male rats were subjected to hemorrhagic shock (40 mmHg for 90 min) and resuscitation. ER-alpha agonist (PPT) or ER-beta agonist (DPN) was administered during resuscitation; rats were sacrificed 24h thereafter. RESULTS: PPT or DPN decreased elevated plasma alpha-glutathione S-transferase levels; however, PPT was more effective. PPT or DPN increased hepatic heat shock protein 32 (Hsp32) mRNA/protein expressions above levels observed after trauma-hemorrhage. PPT reduced hepatic NF-kappaB and AP-1 activity and iNOS expression. Although DPN reduced hepatic NF-kappaB activity, AP-1 activity remained higher than in shams; hepatic iNOS induction remained elevated. PPT/DPN reduced nitrate/nitrite production and iNOS mRNA in Kupffer cells following trauma-hemorrhage; however, these levels in DPN-treated animals remained higher than sham. CONCLUSIONS: Although both PPT and DPN decreased hepatic injury following trauma-hemorrhage, ER-alpha agonist PPT appears to be more effective in downregulating NF-kappaB and AP-1 activity, and iNOS induction. Thus, ER-alpha appears to play a predominant role in mediating the salutary effects of E2 in ameliorating hepatic damage following trauma-hemorrhage.     

Estrogen receptor alpha regulates insulin sensitivity through IRS-1 tyrosine phosphorylation in mature 3T3-L1 adipocytes

There are many clinical and experimental reports demonstrating that estrogens and insulin interact when affecting their target organs. Estrogen receptors consist of two isoforms, estrogen receptors-alpha (ER-alpha) and -beta (ER-beta), but their roles in insulin-induced glucose uptake in mature adipose tissue have yet to be clarified. To evaluate the roles of ER-alpha, expressed predominantly in adipocytes, we have investigated the effects of estradiol (E2), an ER-alpha selective agonist (PPT), and its selective antagonist (MPP) on glucose uptake and insulin action in 3T3-L1 adipocytes. 3T3-L1 adipocytes were exposed to E2 or PPT and/or MPP at different concentrations. The cells were then subjected to 2-deoxy-D-glucose transport assay, western blot analysis, or RT-PCR analysis. Treatment of these cells with E2 or PPT resulted in biphasic effects on glucose transport, that is high (10(-5) M or 3 x 10(-6) M each) and low (10(-8) M) doses produced inhibition and stimulation, respectively. The favorable effect observed at 10(-8) M of E2 was diminished by treatment with MPP. Western bolt analysis revealed that these effects of E2, PPT and MPP paralleled the level of IRS-1 tyrosine phosphorylation. However, IRS-1 serine phosphorylation, suppressor of cytokine signaling (SOCS)-1,-2,-3 and protein tyrosine phosphatase 1B (PTP1B) expression did not change compared to control subjects. Our data clearly show that ER-alpha contributes to insulin stimulated glucose uptake through regulation of the tyrosine phosphorylation of IRS-1 protein.     

alpha-Methylnorepinephrine, a selective alpha2-adrenergic agonist for cardiac resuscitation.

OBJECTIVES: The purpose of this study was to investigate the effects of a selective alpha2-adrenergic agonist, alpha-methylnorepinephrine (alphaMNE) as an alternative vasopressor agent during cardiopulmonary resuscitation (CPR). BACKGROUND: For more than 40 years, epinephrine has been the vasopressor agent of choice for CPR. Its beta- and alpha1-adrenergic effects increase myocardial oxygen consumption, magnify global myocardial ischemia and increase the severity of postresuscitation myocardial dysfunction. METHODS: Ventricular fibrillation (VF) was induced in 20 Sprague-Dawley rats. After 8 min of untreated VF, mechanical ventilation and precordial compression began. AlphaMNE, epinephrine or saline placebo was injected into the right atrium 2 min after the start of precordial compression. As an additional control, one group of animals was pretreated with alpha2-receptor blocker, yohimbine, before injection of alphaMNE. Defibrillation was attempted 4 min later. Left ventricular pressure, dP/dt40, negative dP/dt and cardiac index were measured for an interval of 240 min after resuscitation. RESULTS: Except for saline placebo and yohimbine-treated animals, comparable increases in coronary perfusion pressure were observed after each drug intervention. All animals were successfully resuscitated. Left ventricular diastolic pressure, cardiac index, dP/dt40 and negative dP/dt were more optimal after alphaMNE; this was associated with significantly better postresuscitation survival. Pretreatment with vohimbine abolished the beneficial effects of alphaMNE. CONCLUSIONS: The selective alpha2-adrenergic agonist, alphaMNE, was as effective as epinephrine for initial cardiac resuscitation but provided strikingly better postresuscitation myocardial function and survival.     

Biological role of pituitary estrogen receptors ERalpha and ERbeta on progesterone receptor expression and action and on gonadotropin and prolactin secretion in the rat

Estrogen (E) is a key regulator of the synthesis and secretion of pituitary reproductive hormones [luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL)]. Until recently, it was thought that all biological actions of E at the pituitary were manifested through a single E receptor (R). The pituitary, like many other reproductive tissues, expresses two isoforms of ER, alpha and beta, both activated by E. The relative contribution of alpha and beta forms in E regulatory actions is largely unknown. To this end, 2-week-old ovariectomized (OVX) rats were injected over 3 days with 25 microg estradiol benzoate (EB), 1.5 mg of propylpyrazole triol (PPT), a selective ERalpha agonist, 1.5 mg of the selective ERbeta agonist diarylpropionitrile (DPN) or a combination of PPT and DPN. Controls were injected with 0.2 ml oil. At 10:00 h on the day after treatment, trunk blood was collected to determine serum concentration of LH, FSH and PRL, and pituitaries were processed for RT-PCR analysis of total (A+B) progesterone receptor (PR) mRNA, immunocytochemistry of PR and incubation. Pituitaries from each of the five groups were incubated in DMEM, with or without 20 nM of the antiprogestin at the receptor ZK299, for 3 h with: 10(-8)M 17beta-estradiol, 10(-6)M PPT, 10(-6)M DPN, PPT+DPN or medium alone, respectively, to determine LH, FSH and PRL secretion, and, when challenged with two pulses of 15 min 1 h apart of 10(-8)M gonadotropin-releasing hormone (GnRH) (GnRH self-priming). EB, PPT and PPT+DPN treatments increased PR mRNA and the number and intensity of nuclei immunoreactive (IR) for PR in gonadotropes, and reduced the number of gonadectomy cells. Like E, PPT alone or in combination with DPN stimulated PRL secretion, increased basal and GnRH-stimulated LH and FSH secretion and induced GnRH self-priming in the absence of ZK299 in the incubation medium. DPN alone had only a significant E-like effect on gonadectomy cells and IR-PR, but not on GnRH self-priming. In addition, while DPN lacked an agonistic action on peripheral tissue and serum pituitary reproductive hormones concentration, EB, PPT and PPT+DPN induced similar uterine ballooning and vaginal cornification, and increased and decreased, respectively, serum concentrations of PRL and gonadotropins. Overall, these results indicate that most of these E actions on the pituitary are exerted through the ERalpha isoform. The finding that activation of ERbeta with its selective DPN agonist had an estrogenic effect on IR-PR nuclei, but not on GnRH self-priming, a characteristic ERalpha-mediated effect of E, suggests that the biological action of E at the pituitary may involve both isoforms of ER.     

17Beta-estradiol abrogates apoptosis in murine skeletal muscle cells through estrogen receptors: role of the phosphatidylinositol 3-kinase/Akt pathway

Estrogens can regulate apoptosis in various cellular systems. The present study shows that 17beta-estradiol (E2), at physiological concentrations, abrogates DNA damage, poly (ADP-ribose) polymerase cleavage, and mitochondrial cytochrome c release induced by H2O2 or etoposide in mouse skeletal muscle C2C12 cells. This protective action, which involved PI3K/Akt activation and Bcl-2 associated death agonist (BAD) phosphorylation, was inhibited by antibodies against the estrogen receptor (ER) alpha or beta isoforms, or transfecting siRNA specific for each isoform. The inhibition of the antiapoptotic action of E2 at the mitochondrial level was more pronounced when ER-beta was immunoneutralized or suppressed by mRNA silencing, whereas transfection of C2C12 cells with either ER-alpha siRNA or ER-beta siRNA blocked the activation of Akt by E2, suggesting differential involvement of ER isoforms depending on the step of the apoptotic/survival pathway evaluated. These results indicate that E2 exerts antiapoptotic effects in skeletal muscle cells which are mediated by ER-beta and ER-alpha and involve the PI3K/Akt pathway.     

Hemodynamic effects of naloxone on hemorrhagic shock in the beagle

Naloxone reverses the hypotension in various types of hemorrhagic shock models. What has yet to be firmly established is the mechanism by which naloxone reverses the hypotension. In a canine hemorrhagic shock model, impedance cardiography and invasive methods were used to measure various cardiovascular parameters. All dogs (beagles, 10-15 kg) were bled to and maintained at a mean arterial blood pressure (MAP) of 60 mmHg for 90 min and were then given either naloxone (2 mg/kg; n = 6) or an equivalent volume of saline (n = 6) intravenously (IV). After another 90 min observation period, the shed blood was reinfused. No significant differences in the preshock and shock cardiodynamics were noted between the naloxone and the control animals. During the treatment period, MAP was significantly increased in the naloxone group. There was no increase in cardiac output (CO), stroke volume (SV), end diastolic volume (EDV), dP/dt max, dP/dt/P, or HI (the impedance contractility index) over control animals. The most significant parameter improvement was total peripheral resistance (TPR). The data suggest that naloxone in this hemorrhagic shock model improves hemodynamics primarily by increasing vascular resistance.     

Mechanism of IL-6-mediated cardiac dysfunction following trauma-hemorrhage

Cardiac function is depressed and circulating IL-6 levels increase following trauma-hemorrhage (T-H). Although sustained elevated IL-6 after T-H correlate with poor outcome, the mechanism by which IL-6 produces cardiac dysfunction remains unknown. We hypothesized that IL-6-mediated cardiac depression is due to upregulation of NF-small ka, CyrillicB, ICAM, CINC and neutrophil infiltration. Six groups of male adult rats (275-300 g) were used: sham/T-H + vehicle, sham/T-H + IgG, sham/T-H + anti-IL-6mAb. Following midline laparotomy, 60% of the circulating blood was withdrawn and after 90 min, crystalloid fluid resuscitation was provided. Either normal goat IgG or anti-rat IL-6mAb (16.7 microg/kg BW) was administered intraperitoneally at 30 min after the onset of resuscitation. Two hours after resuscitation, cardiac function was measured, blood samples collected, cardiomyocytes isolated and intracellular IL-6 levels measured by flow cytometry. Cardiac IL-6, IL-6R, gp130, NF-small ka, CyrillicB, Ismall ka, CyrillicB-alpha, and ICAM-1 protein levels were measured in freshly isolated hearts by immunoblotting. Moreover, cardiac MPO activity and CINC-1 and -3 were measured. Cardiac function was depressed and cardiac IL-6, NF-small ka, CyrillicB, ICAM-1, MPO activity, and CINC-1 and -3 were markedly increased after T-H. Administration of anti-IL-6mAb following T-H: 1) improved cardiac output (P<0.05); 2) downregulated cardiac IL-6 levels (P<0.05); 3) attenuated cardiac NF-small ka, CyrillicB, ICAM-1, CINC-1, -3, and MPO activity (P<0.05). Administration of IgG, however, did not significantly influence these parameters. Thus, IL-6-mediated upregulation of cardiac NF-small ka, CyrillicB, ICAM-1, CINC-1, -3, and MPO activity likely contributes to altered cardiac function following T-H and neutralization of IL-6 therefore appears to be an effective and novel adjunct for improving organ/cell function under those conditions.     

Response-specific and ligand dose-dependent modulation of estrogen receptor (ER) alpha activity by ERbeta in the uterus

Estrogen is of great importance in the regulation of uterine function. The aim of this study was to examine the individual physiological roles of each of the two receptors for estradiol, estrogen receptor (ER) alpha and ERbeta, and their potential comodulatory effects on gene expression and uterine growth using recently developed ER subtype-selective agonist ligands. The use of ER subtype-selective ligands provides an alternative, complementary approach to the use of receptor knockout mice. Administration of the ERalpha-selective ligand propyl pyrazole triol (PPT) to immature mice resulted in a significant increase in uterine weight, as well as bromodeoxyuridine incorporation and proliferating cell nuclear antigen expression in luminal epithelial cells. PPT also increased complement component 3, lactoferrin, and glucose-6-phosphate dehydrogenase (G6PDH), and decreased androgen receptor (AR) and progesterone receptor (PR) mRNA levels in uterine tissue, as did estradiol (E(2)). However, when compared with E(2), PPT was less effective in stimulating uterine weight, complement component 3, and G6PDH expression but was as effective as E(2) in regulating lactoferrin, AR, and PR expression. In contrast to the action of the ERalpha agonist PPT, the ERbeta agonist diarylpropionitrile (DPN) did not increase uterine weight or luminal epithelial cell proliferation at a dose that reduced G6PDH and elicited a decrease in PR and AR mRNA and protein expression. Interestingly, DPN reduced the uterine weight stimulation by PPT, and enhanced the effect of PPT in decreasing uterine PR and AR mRNA. These findings with ER subtype-selective ligands indicate that ERalpha is the major regulator of estrogen function in the uterus, but that ERbeta does exert effects on some uterine markers of estrogen action. In addition, ERbeta can modulate ERalpha activity in a response-specific and dose-dependent manner.     

Defeminization of brain functions by a single injection of estrogen receptor α or β agonist in neonatal female rats

Sexual differentiation of brain function is regulated by estrogen in the perinatal period of rodents. However, the role of the estrogen receptor subtypes ERα and ERβ is still in question. Accordingly, the effects of neonatal treatment with the ERα agonist propyl pyrazole triol (PPT) or the ERβ agonist diarylpropionitrile (DPN) on female reproductive functions were investigated in rats. Female rats were injected subcutaneously with 100-500 μg/10 g body weight (b.w.) PPT or DPN, 100 μg/10 g b.w. estradiol (E(2)), or saline at day 5 (birth day = day 1), and then vaginal opening and vaginal smears were examined. On day 60, their ovaries were removed and lordosis behavior was observed after subcutaneous implantation of a silicon tube containing E(2). As a result, in most PPT and all E(2) rats, vaginal opening was advanced and an irregular estrous cycle was observed. In contrast, in most rats of the DPN groups, vaginal opening was comparable to that of the control and there was a regular estrous cycle. Lordosis tests revealed that the mean lordosis quotients (LQs) in the 250- and 500-μg PPT groups was lower than in the saline group, but higher than in the E(2) group. Mean LQs in all DPN groups were comparable to those in the saline group. These results suggest that ERα plays a major role in masculinization of the system regulating the estrous cycle in the rat brain. In behavioral defeminization of the lordosis-regulation system, ERα was also found to be the main target of estrogen.     

High mobility group box 1 induces a negative inotropic effect on the left ventricle in an isolated rat heart model of septic shock: a pilot study.

BACKGROUND: Sepsis can be exacerbated by an inappropriate immune response and the severe impact of this disease on the cardiovascular system is well documented. High mobility group box 1 (HMGB1) protein is an important mediator in the pathogenesis of sepsis and its role in cardiovascular system dysfunction was investigated in an lipopolysaccharide (LPS)-induced rat model of sepsis. METHODS AND RESULTS: Twelve hours after intravenous bolus injections of LPS (5 mg/kg), rats were killed and heart samples were harvested. Immunoblot analysis was performed to assess expression levels of HMGB1 in cardiac myocytes. Left ventricular developed pressure (LVDP) served as a measure of systolic function. LPS administration was associated with an increase in the expression of HMGB1 in cardiac myocytes and a decrease in cardiac function. Hearts from the LPS-treated rats were also perfused with recombinant HMGB1 and cardiac function measured. The dose-dependent effects observed with elevated HMGB1 included decreased LVDP, decreased left ventricular (LV) + dP/dt(max), decreased absolute value of LV- dP/dt(min), and increased LV end-diastolic pressure. CONCLUSIONS: HMGB1 stimulation produces a negative inotropic effect during septic shock, suggesting an important role for this molecule in cardiovascular system dysfunction during sepsis.     

Expression of ER-alpha and ER-beta in the hamster ovary: differential regulation by gonadotropins and ovarian steroid hormones

Spatiotemporal expression patterns of ER-alpha and ER-beta protein and mRNA in hamster ovarian cells during the estrous cycle and following hypophysectomy and selective hormone replacement were evaluated by immunofluorescence, immunoblotting and in situ hybridization analyses. Whereas ER-beta mRNA and protein expression predominated in granulosa cells and ER-alpha expression was in interstitial and thecal cells, overlap in receptor subtype expression across cell types was evident. Both ER subtypes were present from primordial follicle stage onward. ER-alpha mRNA levels and immunoreactivity started increasing from D3:0900 h in interstitial and granulosa cells and peaked on the proestrous (D4:0900 h). Regionalized higher expression of ER-alpha in granulosa cells in and around the forming antrum was evident. Surface epithelial cells were also positive. ER-beta mRNA and protein expression increased markedly in granulosa and interstitial cells on D2:0900 h, reached a peak on D3:0900 h, and then declined sharply on D4:0900 h. No change in ER expression occurred following the preovulatory gonadotropin surge. Whereas FSH or human CG stimulated ER-alpha mRNA and protein expression in hypophysectomized hamsters, only FSH could stimulate ER-beta mRNA and protein, and the effect was significantly attenuated by human CG. ER expression was stimulated by estrogen, but progesterone strongly inhibited estrogen action. These results indicate that ER expression is cell type specific to the larger extent and is critically regulated by reproductive hormones.     

Demonstration of estrogen receptor subtypes alpha and beta in human adipose tissue: influences of adipose cell differentiation and fat depot localization

A novel ER-subtype, the ER-beta has recently been characterized in various tissues, furthermore five isoforms of the ER-beta are known (ER-beta1--ER-beta5). Using immunoblotting and real- time RT-PCR, ER-alpha and beta were studied in human adipose tissue. The expression of ER-alpha mRNA was equal in subcutaneous gluteal adipose tissue, subcutaneous abdominal and intra-abdominal adipose tissue, similar findings were obtained at the protein level. In contrast the amount of ER-beta1 (protein and mRNA) was significantly lower in intra-abdominal adipose tissue as compared with the subcutaneous adipose tissue (five-fold lower in women, P<0.005 and three-fold lower in men, P<0.005) whereas the expression of ER-beta4 and -beta5 mRNA isoforms were significantly higher in gluteal adipose tissue compared to subcutaneous abdominal adipose tissue. No significant gender differences in ER expression was detected in any of the fat depots investigated. During adipocyte differentiation the expression of ER-alpha, -beta4 and -beta5 mRNA declined, whereas, the expression of ER-beta1 mRNA was constant. In conclusion, the existence of ER-beta isoforms in human adipose tissue was demonstrated and the amount of these receptors was dependent upon fat depot localization, with much reduced expression of ER-beta1 in intra-abdominal adipose tissue compared to subcutaneous adipose tissue. These findings may indicate that estrogens could have differentiation and depot specific effects in human adipose tissue.     

Nalbuphine's reversal of hypovolemic shock in the anesthetized rat

Nalbuphine is an agonist-antagonist analgesic chemically related to the opiate agonist oxymorphone and to the opiate antagonist naloxone. Because naloxone has been shown to be beneficial in hemorrhagic shock, this study was undertaken to investigate the hemodynamic effects of nalbuphine in anesthetized rats. The animals were bled 1% of body weight, which caused a significant decrease in mean arterial pressure (MAP) and heart rate (HR). Results indicate an immediate increase in MAP and HR above posthemorrhage values in the rats treated with 1 and 5 mg/kg nalbuphine compared with no improvement for the rats in the saline-treated group. The increases in MAP were sustained for periods up to 120 min postadministration of nalbuphine. Measurements of cardiac output and regional distribution of blood flow indicate that nalbuphine caused an increase in cardiac output, heart rate, stroke volume, and dP/dt with no change in total peripheral resistance.     

Role of estrogen receptor-beta in regulation of vasopressin and oxytocin release in vitro

In rats, the magnocellular neurons that produce vasopressin (VP) and oxytocin (OT) express estrogen receptor-beta (ER-beta). Physiological concentrations of estrogen (E2) inhibit N-methyl-D-aspartate (NMDA)-stimulated VP and OT release from explants of the hypothalamo-neurohypophyseal system (HNS). To determine whether ER-beta mediates inhibition by E2, HNS explants were perifused with and without NMDA (50 microM) in the presence of E2 (50 pg/ml), E2 coupled to BSA (E2:BSA), genistein (100 nM, a phytoestrogen with affinity for ER-beta), or tetrahydrochrysene-R,R,-enantiomer (R,R-THC, a ligand that acts as an agonist on ER-alpha but an antagonist on ER-beta). VP and OT released into the perifusate were measured by RIA. E2 and genistein inhibited NMDA-stimulated VP release, but E2:BSA and R,R,THC were not effective inhibitors. However, R,R,THC blocked E2 inhibition of NMDA-stimulated VP release. The inability of E2:BSA to mimic the effect of E2 indicates that E2 inhibition is not mediated by membrane receptors. The ability of genistein to mimic the effect of E2 suggests that the effect is mediated by ERbeta. This interpretation is supported by the ability of R,R,THC to block but not to mimic the effect of E2. Thus, E2 inhibition of NMDA-stimulated VP and OT release may be mediated by ER-beta.     

Transcriptional activation of heat shock protein 27 gene expression by 17beta-estradiol and modulation by antiestrogens and aryl hydrocarbon receptor agonists

Heat shock protein 27 (Hsp 27) is expressed in mammary tumors and may play a role in tumor growth and response to anti-neoplastic drug therapy. 17beta-Estradiol (E2) induces Hsp 27 mRNA levels in MCF-7 human breast cancer cells, and we have investigated the comparative inhibitory mechanisms using the aryl hydrocarbon receptor (AhR) agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the direct-acting antiestrogen ICI 164,384. TCDD inhibited E2-induced Hsp 27 gene expression and analysis of the Hsp 27 gene promoter showed that the inhibitory response was associated with AhR interactions with a pentanucleotide motif at -3 to +2 in the promoter that corresponded to the core sequence of a dioxin responsive element. In contrast, ICI 164,384 induced Hsp 27 gene expression and reporter gene activity in MCF-7 cells and this represents one of the few examples of the estrogen receptor-alpha (ERalpha) agonist activity of the 'pure' antiestrogen ICI 164,384.     

Estrogen receptor-beta immunoreactivity in luteinizing hormone-releasing hormone neurons of the rat brain.

Feedback regulation of luteinizing hormone-releasing hormone (LHRH) neurons by estradiol plays important roles in the neuroendocrine control of reproduction. Recently, we found that the majority of LHRH neurons in the rat contain estrogen receptor-beta (ER-beta) mRNA, whereas, they seemed to lack ER-alpha mRNA expression. In addition, we observed nuclear uptake of (125)I-estrogen by a subset of these cells. These data suggest that ER-beta is the chief receptor isoform mediating direct estrogen effects upon LHRH neurons. To verify the translation of ER-beta protein within LHRH cells, the present studies applied dual-label immunocytochemistry (ICC) to free-floating sections obtained from the preoptic area of rats. The improved ICC method using the silver-gold intensification of nickel-diaminobenzidine chromogen, enabled the observation of nuclear ER-beta-immunoreactivity in the majority of LHRH cells. The incidence of ER-beta expression was similarly high in LHRH neurons of ovariectomized female (87.8 +/- 2.3%, mean +/- SEM), estradiol-primed female (74.9 +/- 3.2%) and intact male (85.0 +/- 4.7%) rats. The presence of ER-beta mRNA, ER-beta immunoreactivity and (125)I-estrogen binding sites in LHRH neurons of the rat provide strong support for the notion that these cells are directly regulated by estradiol, through ER-beta. The gene targets and molecular mechanisms of this regulation remain unknown.     

Depressed in vivo myocardial reactivity to dobutamine in streptozotocin diabetic rats: influence of exercise training

To assess the effects of chronic diabetes on in vivo myocardial reactivity to beta 1 adrenergic receptor stimulation and to evaluate the therapeutic effect of exercise training in preventing the cardiac abnormalities induced by diabetes four groups of rats were studied: sedentary control, trained control, sedentary diabetic, and trained diabetic. Trained rats were adapted to treadmill running before the induction of diabetes with streptozotocin 55 mg.kg-1 iv. The duration, speed, and grade of exercise were then progressively increased during eight weeks of training until the rats could run for 90 min at 18 m/min, 5% grade. A training effect was confirmed by an increase in plantaris muscle cytochrome oxidase activity. In vivo cardiac contractile performance was assessed by intracardiac catheterisation. Heart rate, left intraventricular peak systolic pressure, and positive and negative dP/dt were measured under basal conditions and after the intravenous administration of dobutamine 10(-10) to 5 x 10(-7) mol.kg-1 body weight. Under basal conditions, there were no differences among the four groups in left intraventricular peak systolic pressure, positive dP/dt, and heart rate, but negative dP/dt was lower in both diabetic groups. The response to dobutamine of the sedentary diabetic group, as reflected in the measured cardiodynamic variables, was significantly attenuated compared with that of the sedentary control group. Exercise training tended to improve cardiac function towards the level detected in the sedentary controls; however, the differences between sedentary and trained diabetic groups were not statistically significant. Exercise training also did not significantly alter the response of the control group to dobutamine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Noninvasive estimation of max (dP/dt) of the left ventricle based on maximum aortic flow acceleration as measured by pulsed Doppler echocardiography

To obtain an index of left ventricular contractility, cardiac catheterization is necessary. In the present study, we ascertained whether max(dP/dt) could be obtained noninvasively in vivo based on the theoretical equation, max(dP/dt) not equal to rho cmax(du/dt), where rho is the density of blood, c is the pulse wave velocity of the aorta and max(du/dt) is the maximum acceleration of the aortic blood flow. This equation is based on the theory of pulse wave propagation, and was established in animal experiments. We further attempted to clarify the clinical usefulness of rho cmax(du/dt) by examining the effects of afterload and preload on rho cmax(du/dt). Twenty-seven patients without stenosis of their aortic valves and left ventricular outflow tracts were observed. During cardiac catheterization, we measured max(dP/dt) using a catheter-tip micromanometer, max (du/dt) using pulsed Doppler echocardiography and pulse wave velocity by simultaneously recording the femoral pulse wave and the carotid pulse wave. The measurements were performed at rest, before and after an increase in contractility with dobutamine administration, an increase in afterload with methoxamine administration and an increase in preload by leg elevation. There was good linear correlation (Y = 0.95X + 7.51, r = 0.84, p less than 0.0005) between max(dP/dt)[X] and rho cmax(du/dt)[Y] at rest. When the contractility was changed, rho cmax(du/dt) reflected changing of max(dP/dt). Moreover, when the afterload and preload were increased, the changing pattern of rho cmax(du/dt) was similar to that of max(dP/dt). Max(du/dt), index of cardiac performance previously proposed, showed a different changing pattern than max(dP/dt), indicating that max(du/dt) was influenced substantially by loading conditions. These results indicated that we can obtain max(dP/dt) noninvasively and reliably by measuring rho cmax(du/dt).