Soluble metals associated with residual oil fly ash increase morbidity and lung injury after bacterial infection in rats

Inhalation of residual oil fly ash (ROFA) has been shown to impair lung defense mechanisms in laboratory animals and susceptible populations. Bioavailability of soluble transition metals has been shown to play a key role in lung injury caused by ROFA exposure. The goal of this study was to evaluate the effect of soluble metals on lung defense and injury in animals preexposed to ROFA followed by pulmonary challenge with a bacterial pathogen. ROFA was suspended in saline (ROFA-TOTAL), incubated overnight at 37 degrees C, and separated by centrifugation into soluble (ROFA-SOL) and insoluble (ROFA-INSOL) fractions. A portion of the soluble sample was treated with the metal-binding resin Chelex for 24 h at 37 degrees C. Sprague-Dawley rats were intratracheally dosed at d 0 with ROFA-TOTAL (1.0 mg/100 g body weight), ROFA-INSOL, ROFA-SOL, saline, saline + Chelex, or ROFA-SOL + Chelex. At d 3, 5 x 10(5) Listeria monocytogenes were intratracheally instilled into rats from each treatment group. At d 6, 8, and 10, left lungs were removed, homogenized, and cultured to assess bacterial clearance. Histopathological analysis was performed on the right lungs. Pulmonary exposure of ROFA-TOTAL or ROFA-SOL before infection led to a marked increase in lung injury and inflammation at all three time points after inoculation, and an increase in morbidity in comparison to saline control rats. Treatment with ROFA-INSOL, saline + Chelex, or ROFA-SOL + Chelex caused no significant increases in lung damage and morbidity when compared to control. By d 10, the ROFA-SOL and ROFA-TOTAL groups had approximately 200-fold more bacteria in the lung than saline control, indicating the inability of these groups to effectively respond to the infection. None of the other treatment groups had significant impairments in bacterial clearance when compared to saline. In conclusion, exposure to ROFA-TOTAL and ROFA-SOL significantly suppressed the lung response to infection. These results suggest that soluble metals present in ROFA may play a key role in increased susceptibility to pulmonary infection in exposed populations.     

Lung injury from intratracheal and inhalation exposures to residual oil fly ash in a rat model of monocrotaline-induced pulmonary hypertension.

A rat model of monocrotaline (MCT)-induced pulmonary injury/hypertension has been recently used in particulate matter (PM) health effects studies, however, results have been equivocal. Neither the mechanism by which mortality occurs in this model nor the variation in response due to differences in PM exposure protocols (i.e., a bolus dose delivered intratracheally versus a similar cumulative dose inhaled over three days) have been fully investigated. Sprague Dawley rats (SD, 60 d old; 250-300 g) were injected with either saline (healthy) or MCT, 60 mg/kg, i.p. (to induce pulmonary injury/hypertension). Ten days later they were exposed to residual oil fly ash (ROFA), either intratracheally (IT; saline, 0.83 or 3.33 mg/kg) or by nose-only inhalation (15 mg/m3 x 6 h/d x 3 d). Lung histology, pulmonary cytokine gene expression (0 and 18 h postinhalation), and bronchoalveolar lavage fluid (BALF) markers of injury were analyzed (24 and 96 h post-IT; or 18 h post-inhalation). Data comparisons examined three primary aspects, 1) ROFA IT versus inhalation effects in healthy rats; 2) pulmonary injury caused by MCT; and 3) exacerbation of ROFA effects in MCT rats. In the first aspect, pulmonary histological lesions following ROFA inhalation in healthy rats were characterized by edema, inflammatory cell infiltration, and thickening of alveolar walls. Increases in BALF markers of lung injury and inflammation were apparent in ROFA-IT or nose-only exposed healthy rats. Increased IL-6, and MIP-2 expression were also apparent in healthy rats following ROFA inhalation. In regards to the second aspect, MCT rats exposed to saline or air showed perivascular inflammatory cell infiltrates, increased presence of large macrophages, and alveolar thickening. Consistently, BALF protein, and inflammatory markers (macrophage and neutrophil counts) were elevated indicating pulmonary injury. In regards to the third aspect, 58% of MCT rats exposed to ROFA IT died within 96 h regardless of the dose. No mortality was observed using the inhalation protocol. ROFA inhalation in MCT rats caused exacerbation of lung lesions such as increased edema, alveolar wall thickening, and inflammatory cell infiltration. This exacerbation was also evident in terms of additive or more than additive increases in BALF neutrophils, macrophages and eosinophils. IL-6 but not MIP-2 expression was more than additive in MCT rats, and persisted over 18 h following ROFA. IL-10 and cellular fibronectin expression was only increased in MCT rats exposed to ROFA. In summary, only the bolus IT ROFA caused mortality in the rat model of lung injury/hypertension. Exacerbation of histological lesions and cytokine mRNA expression were most reflective of increased ROFA susceptibility in this model.     

Soluble metals in residual oil fly ash alter innate and adaptive pulmonary immune responses to bacterial infection in rats

The soluble metals of the pollutant, residual oil fly ash (ROFA), have been shown to alter pulmonary bacterial clearance in rats. The goal of this study was to determine the potential effects on both the innate and adaptive lung immune responses after bacterial infection in rats pre-exposed to the soluble metals in ROFA. Sprague-Dawley rats were intratracheally dosed (i.t.) at day 0 with ROFA (R-Total) (1.0 mg/100 g body weight), the soluble fraction of ROFA (R-Soluble), the soluble sample subject to a chelator (R-Chelex), or phosphate-buffered saline (Saline). On day 3, rats were administered an i.t. dose of 5 x 10(4)Listeria monocytogenes. On days 6, 8, and 10, bacterial pulmonary clearance was monitored and bronchoalveolar lavage (BAL) was performed on days 3 (pre-infection), 6, 8, and 10. A concentrated first fraction of lavage fluid was retained for analysis of lactate dehydrogenase and albumin to assess lung injury. BAL cell number, phenotype, and production of reactive oxygen (ROS) and nitrogen species (RNS) were assessed, and a variety of cytokines were measured in the BAL fluid. Rats pre-treated with R-Soluble showed elevated lung injury/cytotoxicity and increased cellular influx into the lungs. R-Soluble-treatment also altered ROS, RNS, and cytokine levels, and caused a degree of macrophage and T cell inhibition. These effects of R-Soluble result in increased pulmonary bacterial burden after infection. The results suggest that soluble metals in ROFA increase lung injury and inflammation, and alter both innate and adaptive pulmonary immune responses.     

Airway hyperresponsiveness caused by aerosol exposure to residual oil fly ash leachate in mice

Particulate air pollution is associated with exacerbation of asthma and other respiratory disorders. This study sought to further characterize the pulmonary effects of residual oil fly ash (ROFA), an experimentally useful surrogate for combustion-derived particulates in ambient air. Mice were exposed to aerosols of the soluble leachate of residual oil fly ash (ROFA-s). Physiologic testing of airway function (non invasive plethysmography) showed increased Penh, an index of airway hyperresponsiveness (AHR), in a time- and dose-dependent manner after exposure to ROFA-s. BAL analysis showed a minor influx of neutrophils, which was maximal at 12 h after exposure and essentially resolved by the time point of maximal AHR (48 h after exposure). The AHR caused by ROFA-s was reproduced by a mixture of its major metal components (Ni, V, Zn, Co, Mn, Cu) but not by any individual metal alone. Systemic pretreatment of mice with the antioxidant dimethylthiourea abrogated ROFA-s-mediated AHR. Analysis of mice of varying ages showed that ROFA-s had no marked effect on airway responsiveness of 2-wk-old mice, in contrast to the AHR seen in 3- and 8-wk old mice. ROFA-s-mediated AHR was unchanged in neurokinin 1 receptor knockout mice and in mice treated with an neurokinin antagonist, arguing against a role for this mediator in ROFA-s-mediated effects. Data indicate that ROFA-s mediates AHR in mice through antioxidant-sensitive mechanisms that require multiple metal constituents. Maturational differences in susceptibility to ROFA-induced AHR may be useful for further studies of mechanisms of particle effects.     

Acute pulmonary and moderate cardiovascular responses of spontaneously hypertensive rats after exposure to single-wall carbon nanotubes

As a novel kind of nanomaterial with wide potential applications, the adverse effects of carbon nanotubes (CNTs) have recently received significant attention after respiratory exposure. In this study, single-wall carbon nanotubes (SWCNTs) containing different metal contents were intratracheally instilled into lungs of spontaneously hypertensive rats. Pulmonary and cardiovascular system alterations were evaluated at 24 and 72 h post-instillation. Biomarkers of inflammation, oxidative stress and cell damage in the bronchoalveolar lavage fluid (BALF) were increased significantly 24 h post-exposure of SWCNTs. The increased endothelin-1 levels in BALF and plasma and angiotensin I-converting enzyme in plasma suggested endothelial dysfunction in the pulmonary circulation and peripheral vascular thrombosis. These findings suggest that respiratory exposure to SWCNTs can induce acute pulmonary and cardiovascular responses and individuals with existing cardiovascular diseases are very susceptible to SWCNTs exposure. The co-existence of metal residues in SWCNTs can aggravate the adverse effects.     

Electrocardiographic changes during exposure to residual oil fly ash (ROFA) particles in a rat model of myocardial infarction.

Epidemiological studies have reported a positive association of short-term increases in ambient particulate matter (PM) with daily mortality and hospital admissions for cardiovascular disease. Although patients with cardiopulmonary disease appear to be most at risk, particulate-related cardiac effects following myocardial infarction (MI) have not been examined. To improve understanding of mechanisms, we developed and tested a model for investigating the effects of inhaled PM on arrhythmias and heart rate variability (HRV), a measure of autonomic nervous system activity, in rats with acute MI. Left-ventricular MI was induced in 31 Sprague-Dawley rats by thermocoagulation of the left coronary artery; 32 additional rats served as sham-operated controls. Diazepam-sedated rats were exposed (1 h) to residual oil fly ash (ROFA), carbon black, or room air at 12-18 h after surgery. Each exposure was immediately preceded and followed by a 1-h exposure to room air (baseline and recovery periods, respectively). Lead-II electrocardiograms were recorded. In the MI group, 41% of rats exhibited one or more premature ventricular complexes (PVCs) during the baseline period. Exposure to ROFA, but not to carbon black or room air, increased arrhythmia frequency in animals with preexisting PVCs. Furthermore, MI rats exposed to ROFA, but not to carbon black or room air, decreased HRV. There was no difference in arrhythmia frequency or HRV among sham-operated animals. These results underscore the usefulness of this model for elucidating the physiologic mechanisms of pollution-induced cardiovascular arrhythmias and contribute to defining the specific constituents of ambient particles responsible for arrhythmias.     

In vivo short‐term exposure to residual oil fly ash impairs pulmonary innate immune response against environmental mycobacterium infection

Epidemiological studies have shown that pollution derived from industrial and vehicular transportation induces adverse health effects causing broad ambient respiratory diseases. Therefore, air pollution should be taken into account when microbial diseases are evaluated. Environmental mycobacteria (EM) are opportunist pathogens that can affect a variety of immune compromised patients, which impacts significantly on human morbidity and mortality. The aim of this study was to evaluate the effect of residual oil fly ash (ROFA) pre‐exposure on the pulmonary response after challenge with opportunistic mycobacteria by means of an acute short‐term in vivo experimental animal model. We exposed BALB/c mice to ROFA and observed a significant reduction on bacterial clearance at 24 h post infection. To study the basis of this impaired response four groups of animals were instilled with (a) saline solution (Control), (b) ROFA (1 mg kg^?1 BW), (c) ROFA and EM‐infected (Mycobacterium phlei, 8 × 10⁶ CFU), and (d) EM‐infected. Animals were sacrificed 24 h postinfection and biomarkers of lung injury and proinflammatory madiators were examined in the bronchoalveolar lavage. Our results indicate that ROFA was able to produce an acute pulmonary injury characterized by an increase in bronchoalveolar polymorphonuclear (PMN) cells influx and a rise in O₂^? generation. Exposure to ROFA before M. phlei infection reduced total cell number and caused a significant decline in PMN cells recruitment (p < 0.05), O₂^? generation, TNFα (p < 0.001), and IL‐6 (p < 0.001) levels. Hence, our results suggest that, in this animal model, the acute short‐term pre‐exposure to ROFA reduces early lung response to EM infection. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 589–596, 2015.     

Phosphatidylcholine metabolism in lung microsomes and lung surfactant of rats exposed intratracheally to coal fly ash

The effect of intratracheal administration of fly ash has been studied on lung microsomal and lung surfactant phosphatidylcholine (PC) metabolism in rats using [methyl-14C]choline and [methyl-14C]methionine. Fly-ash administration significantly increased total phospholipids, PC, phosphatidylethanolamine (PE), and phosphatidylglycerol (PG) of lung surfactant. Fly-ash administration stimulated the formation of lung microsomal PC (as measured by the incorporation of labeled precursors) both by the cytidine 5'-diphosphate (CDP)-choline pathway and by the N-methylation pathway, but this stimulation was fourfold higher in the latter case and only twofold higher in the former as compared to the control. Likewise, the secretion of PC formed by the N-methylation pathway was sixfold higher as compared to the control whereas secretion of PC formed by the CDP-choline pathway was only threefold higher as compared to the control. Fly-ash administration further increased total saturation and decreased unsaturation in PC, PE, and lysophosphatidylcholine (LPC) of lung and in PC, PE, LPC, and PG of lung surfactant as compared to the controls.     

Cardiopulmonary responses of Wistar Kyoto, spontaneously hypertensive, and stroke-prone spontaneously hypertensive rats to particulate matter (PM) exposure

Humans with underlying cardiovascular disease, including stroke, are more susceptible to ambient particulate matter (PM)-induced morbidity and mortality. We hypothesized that stroke-prone spontaneously hypertensive rats (SHRSP) would be more susceptible than healthy Wistar Kyoto (WKY) rats to PM-induced cardiac oxidative stress and pulmonary injury. We further postulated that PM-induced injury would be greater in SHRSP than in spontaneously hypertensive rats (SHR) based on the greater disease severity in SHRSP than SHR. First, male WKY and SHRSP were intratracheally (IT) instilled with saline or 1.11, 3.33, or 8.33 mg/kg of oil combustion PM and responses were analyzed 4 or 24 h later. Second, SHR and SHRSP were IT instilled with saline or 3.33 or 8.33 mg/kg of the same PM and responses were analyzed 24 h later. Pulmonary injury and inflammation were assessed in bronchoalveolar lavage fluid (BALF) and cardiac markers in cytosolic and mitochondrial fractions. BALF neutrophilic inflammatory response was induced similarly in all strains following PM exposure. BALF protein leakage, gamma-glutamyl transferase, and N-acetylglucosaminidase activities, but not lactate dehydrogenase activity, were exacerbated in SHRSP compared to WKY or SHR. Pulmonary cytosolic and cardiac mitochondrial ferritin levels decreased, and cardiac cytosolic superoxide dismutase (SOD) activity increased in SHRSP only. Pulmonary SOD activity decreased in WKY and SHRSP. Cardiac mitochondrial isocitrate dehydrogenase (ICDH) activity decreased in PM-exposed WKY and SHR; control levels were lower in SHRSP than SHR or WKY. In summary, strain-related differences exist in pulmonary protein leakage and oxidative stress markers. PM-induced changes in cardiac oxidative stress sensitive enzymes are small, and appear only slightly exacerbated in SHRSP compared to WKY or SHR. Multiple biological markers may be differentially affected by PM in genetic models of cardiovascular diseases. Preexisting cardiovascular disease may influence susceptibility to PM pulmonary and cardiac health effects in a disease-specific manner.     

Acute exposure to cadmium causes severe liver injury in rats

The acute cardiotoxicity of Cd was studied in rats injected iv with 3.9 mg Cd/kg (LD99). Electrocardiogram, blood pressure, and heart rate were recorded intermittently from 9 hr after Cd administration until death. No changes were observed in cardiac indices. Microscopic examination of the major tissues revealed histologically normal myocardium but severely damaged liver. To evaluate further the observed hepatotoxic effects of Cd, time course (1 to 10 hr after 3.9 mg Cd/kg, iv) and dose-response (10 hr after 0.9 to 3.9 mg Cd/kg, iv) studies were conducted. Liver was examined for histopathologic changes; plasma enzyme activities of aspartate (AST) and alanine (ALT) aminotransferases and alkaline phosphatase (AP) were determined to assess liver damage. Pronounced eosinophilia, hepatocyte swelling, and an increase of mitotic figures in hepatocytes were present within 1 hr after Cd. Increased AST and ALT activities were also observed, but AP activity and plasma glucose concentration were unchanged. At later times, severe liver injury was evidenced by necrosis of hepatocytes, striking elevation of serum enzymes (AST, ALT, and AP), and a 50% decrease in plasma glucose concentration. Doseresponse data indicated that doses greater than 1.1 mg Cd/kg produced pathologic changes similar to those observed in the time course study 1 hr after 3.9 mg Cd/kg. Doses above 3.5 mg Cd/kg caused massive hepatic necrosis and increased ALT, AST, and AP activities 60-, 100-, and 3-fold, respectively. A 50% decrease in plasma glucose concentration was also observed at doses above 2.9 mg Cd/kg. These results do not suggest that Cd is cardiotoxic after acute exposure, but rather that the liver is a major target organ for acute Cd toxicity.     

Metabolism and hepatorenal toxicity due to repeated exposure to styrene in spontaneously hypertensive rats (SHR)

Groups of adult male rats (5 rats per group), either normotensive (WKY) or spontaneously hypertensive (SHR), were exposed by inhalation to 0, 821, and 3018 ppm styrene, 5 h per day for 3 consecutive days. After the exposure, the urines were collected for 24 h and the animals were then sacrificed. The various biochemical parameters of hepatorenal toxicity due to styrene as well as its urinary metabolites were measured. Hepatotoxicity due to styrene was not further increased at any exposure level due to hypertension. However, repeated exposure of SHR rats to 3018 ppm styrene showed significant increases in the urinary excretion of gamma-glutamyl transpeptidase, proteins, and volume of urine, compared to WKY treated rats, whereas no such changes were observed due to repeated exposure to 821 ppm styrene. Studies of in vivo metabolism of styrene at higher exposure level showed significant decrease in the urinary excretion of mandelic, phenylglyoxylic, and hippuric acids in SHR rats compared to WKY-treated rats, suggesting an inhibition of deactivation of styrene reactive intermediate involving the epoxide hydrase pathway due to hypertension. At the same time, a significant increase in the urinary excretion of a potential nephrotoxic metabolite of styrene (e.g., mercapturates or thioethers) was observed in SHR-treated rats when compared to WKY-treated rats. These results demonstrate that spontaneous hypertension has the potential to further increase the nephrotoxicity due to repeated exposure to styrene, and the metabolism of styrene plays an important role in modifying such toxicity in the hypertensive state.     

Acute inhalation exposure to vaporized methamphetamine causes lung injury in mice

Methamphetamine (MA) is currently the most widespread illegally used stimulant in the United States. Use of MA by smoking is the fastest growing mode of administration, which increases concerns about potential pulmonary and other medical complications. A murine exposure system was developed to study the pulmonary affects of inhaled MA. Mice were exposed to 25-100 mg vaporized MA and assessments were made 3 h following initiation of exposure to model acute lung injury. Inhalation of MA vapor resulted in dose-dependent increases in MA plasma levels that were in the range of those experienced by MA users. At the highest MA dose, histological changes were observed in the lung and small but significant increases in lung wet weight to body weight ratios (5.656 +/- 0.176 mg/g for the controls vs. 6.706+/- 0.135 mg/g for the 100 mg MA-exposed mice) were found. In addition, there was 53% increase in total protein in bronchoalveolar lavage (BAL) fluid, greater than 20% increase in albumin levels in the BAL fluid, greater than 2.5-fold increase in lactate dehydrogenase levels in the BAL fluid, and reduced total BAL cell numbers (approximately 77% of controls). Levels of the early response cytokines tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 were dose-dependently increased in BAL fluid of MA-exposed mice. Exposure to 100 mg MA significantly increased free radical generation in the BAL cells to 107-146% of controls and to approximately 135% of the controls in lung tissue in situ. Together, these data show that acute inhalation exposure to relevant doses of volatilized MA is associated with elevated free radical formation and significant lung injury.     

Sex and strain-based inflammatory response to repeated tobacco smoke exposure in spontaneously hypertensive and Wistar Kyoto rats

Context: Approximately four million people die every year from chronic obstructive pulmonary disease (COPD), with more than 80% of the cases attributed to smoking.

Object: The purpose of this study was to examine the rat strain and sex-related differences and the extended tobacco smoke exposure to induce lung injury and inflammation with the goal of finding a suitable rodent model to study COPD.

Methods: Male and female spontaneously hypertensive (SH) and male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or to tobacco smoke (TS: 90?mg/m³ particulate concentration) for 6?h/day, three days/week for 4 or 12 weeks.

Results: Male SH rats demonstrated an enhanced, persistent inflammatory response compared to female SH and male WKY rats with extended TS exposure. Following four weeks of TS exposure, male SH rats had significantly increased total leukocytes and macrophage numbers, levels of TNF-alpha and elevated lactate dehydrogenase activity in bronchoalveolar lavage fluid compared with female SH, male WKY rats and corresponding controls. After 12 weeks of TS exposure, male SH rats continued to show significant increase in inflammatory cells and TNF-alpha, as well as IL-6 mRNA lung expression. In addition, the alveolar airspace of male SH rats exposed to TS was significantly enlarged compared to their FA controls, female SH and WKY rats.

Conclusion: The male SH rat demonstrates greater cellular, inflammatory and structural changes highly reminiscent of COPD compared to female SH and male WKY rats, suggesting that the male SH rat is an optimal rodent model to study COPD.     

Tachyphylaxis to 5-hydroxytryptamine in perfused kidneys from spontaneously hypertensive and normotensive rats

Isolated perfused kidneys from 4- to 6-month-old spontaneously hypertensive rats (SHR, Japanese strain) exhibit increased "vascular reactivity" to 5-hydroxytryptamine (5-HT) and a slower rate of development of tachyphylaxis to this substance when compared with kidneys from normotensive Wistar-Kyoto (WKY) rats. We investigated the possibility that the reduced rate of development of tachyphylaxis could be related to a interaction of 5-HT with adrenergic mechanisms or with endogenous 5-HT. Tachyphylaxis was induced by repeated administration of 5-HT to kidneys from SHR and WKY rats. This procedure did not affect vasoconstrictor responses evoked by norepinephrine. The development of tachypylaxis to 5-HT in kidneys from SHR and WKY rats was not changed by chemical sympathectomy with 6-hydroxydopamine. Treatment of SHR with para-chlorophenylalanine did not affect their blood pressure or the development of tachyphylaxis to 5-HT. These results indicate that delayed tachyphylaxis to 5-HT in kidneys of SHR is not due to an interference with adrenergic mechanisms and does not depend on endogenous 5-HT levels. The phenomenon represents an unusual modification of vascular smooth muscle exposed to chronic high pressure, but it is unlikely that the vasoconstrictor effects of 5-HT contribute to the maintenance of hypertension in the SHR.     

Acute tolerance to the hypotensive effect of pindolol in spontaneously hypertensive rats (SHR)

The development and mechanism of acute tolerance to hypotension produced by pindolol in conscious SHR were examined. At a daily dose of 3 mg/kg, i.p., the hypotensive effect of pindolol (50 +/- 4 mmHg) on the first day was attenuated to 12 +/- 2 mmHg on the fourth day. The development of this acute tolerance was not reduced by combined administration with captopril or trichlormethiazide. The hypotensive effect of pindolol was not reduced by repeated administration of isoproterenol. Thus, activation of the renin-angiotensin system, fluid retention and beta-adrenoceptor subsensitivity seemed to be ruled out from the mechanism of this acute tolerance to pindolol. SHR tolerant to pindolol displayed marked hypotensive effects to prazosin, clonidine, hydralazine, nifedipine and captopril, which were similar to those in saline-treated SHR. However, the depressor response to isoproterenol was markedly reduced in SHR tolerant to pindolol. The correlation between the hypotensive responses to isoproterenol (X) and pindolol (Y) in these SHR could be expressed by: Y = 1.00 X + 0.56, gamma = 0.837 (P less than 0.001). Therefore, acute tolerance to pindolol seemed to be mainly due to "autoblockade" by the remaining pindolol in the body.     

Cardiovascular responses to morphiceptin in spontaneously hypertensive and normotensive rats

In the urethane anesthetized spontaneously hypertensive rats (SHR) intraventricular injections of morphiceptin produced dose-related increase in heart rate and blood pressure. In contrary, intraventricular administration of morphiceptin in Wistar rats induced a fall in blood pressure and heart rate. Yohimbine antagonized pressor responses to morphiceptin in SHR. Naloxone counteracted both the stimulatory effects of morphiceptin in SHR as well as hypotensive responses in Wistar rats. Bilateral vagotomy blocked depressant action of morphiceptin in normotensive but failed to alter the pressor effects in SHR rats. After systemic injections of morphiceptin a fall in heart rate and blood pressure was obtained in both strains.     

Rapeseed oil ingestion and exacerbation of hypertension-related conditions in stroke prone spontaneously hypertensive rats

Two groups of 20 stroke prone spontaneously hypertensive rats (SHRSP) at 5 weeks old were fed a diet containing 10 w/w% rapeseed (canola) oil or soybean oil as the only dietary fat, and given drinking water containing 1% NaCl. Life span of the canola oil group (62+/-2 days) was shorter than that of the soybean oil group (68+/-3 days). Stroke-related symptoms were observed in every animal, but the onset of those in the canola oil group, at 47+/-1 days after starting the administration was earlier than that in the soybean oil group, 52+/-2 days. Incidence of cerebral hemorrhage was similar in these groups, and no differences were found between lesions of organs in the groups. In another experiment, two groups of ten SHRSP at 5 weeks of age were fed the defatted diet and given canola oil or soybean oil by gavage at 10 w/w% of consumed food for 4 weeks without NaCl loading. After the 4-week administration, mean systolic blood pressure in the canola oil group and the soybean oil group were 233+/-2 and 223+/-0.3 mmHg, respectively. Phytosterol levels in both plasma and erythrocyte membranes reflected those contained in the oils ingested. Na(+), K(+)-ATPase activities in the brain, heart and kidney were enhanced in the canola oil group. These results indicate that promotion of hypertension-related deterioration in organs is likely to have relevance to the short life span in the canola oil group. Enhanced Na(+), K(+)-ATPase activity by phytosterols in the oil ingested may play a role in these changes.     

Blood pressure and vascular reactivity changes in spontaneously hypertensive rats fed fish oil.

1. To examine possible mechanisms of antihypertensive effects of feeding fish oil rich in n-3 fatty acids, we have studied vascular reactivity of aortic rings and perfused mesenteric resistance vessels of spontaneously hypertensive rats (SHR) given such a diet. 2. In two experiments, rats were fed a semi-synthetic diet containing either 'fish oil' (10 and 20% by weight) or hydrogenated coconut oil (control) (10 and 20%) for 4 weeks. 3. Blood pressure rose significantly less in the fish oil group than in controls in both experiments. 4. Aortic rings from control rats showed endothelium-dependent relaxations to low concentrations of acetylcholine (ACh) but relaxed less at higher concentrations. In contrast, rings from the fish oil group had relaxations which increased through the range of concentrations used. Indomethacin (10 microM) also increased the relaxation responses seen in rings from control rats, suggesting that fish oil inhibits a contractile cyclo-oxygenase product. This contractile substance may be thromboxane A2 (TxA2) or its endoperoxide precursor, prostaglandin H2 (PGH2) as aortic incubates and serum levels of TxB2 (the stable product of TxA2) were greatly reduced in fish oil-fed rats, and the decrease of relaxant responses to high concentrations of ACh were also blocked by a TxA2/PGH2 receptor blocker (SQ 29548). 5. In contrast to aortic rings, perfused preconstricted mesenteric resistance vessels of control rats relaxed to ACh in a similar fashion to tissues from fish oil-fed rats. However, in this preparation, fish oil feeding enhanced relaxations to sodium nitroprusside (SNP) and contractile responses to noradrenaline were less than controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pumpkin-seed oil modulates the effect of felodipine and captopril in spontaneously hypertensive rats.

Natural products like pumpkin-seed oil (PSO) may modify the potency of the calcium antagonist felodipine (FEL) or angiotensin-converting enzyme inhibitor (ACE-inhibitor), captopril (CPT) in modulating the biochemical derangement in blood, heart and kidney as well as blood pressure and heart rate of spontaneously hypertensive rats (SHR) were investigated. SHR were treated orally with FEL at a dose of 0. 45 mg kg(-1) body wt. or CPT at a dose of 9 mg kg(-1) body wt. once daily for 4 weeks. PSO was administered at a dose of 40 mg kg(-1) body wt. alone or with FEL or CPT in the previous respective dose regimen for the same period to SHR. This study showed that hypertension induced increments the content of malondialdehyde (MDA) by 55% and 38% as well as the activity of glutathione peroxidase (GSH-Px) by 26% and 23% in heart and kidney, respectively, accompanied by reductions in the activity of myocardial superoxide dismutase (SOD) from 3.40+/-0.17 to 2.42+/-0.19 U mg protein(-1)and contents of glutathione (GSH) and protein thiols (PrSHs) in different tissues of SHR as compared to normotensive rats. Treatment of SHR with FEL or CPT monotherapy or combined with PSO produced improvement in the measured free radical scavengers in the heart and kidney. Our results also showed that pretreatment of SHR with PSO for 4 weeks then i.v. administration of FEL or CPT produced a significant beneficial hypotensive action. The results were explained in the light of the antioxidant properties of PSO. Therefore, it is concluded that concomitant administration of FEL or CPT with natural antioxidants can yield a beneficial therapeutic effect and retard the progression of hypertension.     

Different responses of mesenteric artery from normotensive and spontaneously hypertensive rats to nitric oxide and its redox congeners

The conversion of nitric oxide (NO*) into its congeners nitrosonium (NO(+)) and nitroxyl (HNO/NO(-)) ions may have important consequences for signal transduction and physiological responses. Manganese-containing superoxide dismutase (MnSOD) may convert NO. into its redox congeners. In our current work, we have examined the mechanism of sodium nitroprusside (SNP)-induced relaxation of arteries, with or without endothelium, from both normotensive and spontaneously hypertensive (SH) rats in the absence and presence of MnSOD. SNP induced a greater degree of relaxation in normotensive than in SH rats. MnSOD antagonized SNP-induced relaxation and effect was greater in normotensive than hypertensive rats. However, MnSOD even potentiated SNP-induced relaxation in mesenteric arteries with endothelium from SH rats. Our results indicate that HNO/NO(-)-mediated relaxation is more effective in mesenteric artery smooth muscle from SH rats than from normotensive rats and that vascular dysfunction in SH rats is not solely endothelium-derived but involves changes in vascular smooth muscles.