Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ISOLATION PERFUSION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57Linked to original sources
PubMed1979

Autoreversal of bradykinin response in the perfused isolated canine hind limb.

The vascular effects of synthetic bradykinin were studied in perfused isolated canine hind limb preparations. Repeated low doses of bradykinin or high doses administered at sufficiently long time intervals elicited dose-related hypotensive responses. In contrast, administration of bradykinin at short time intervals led first to diminishing hypotensive responses followed by frank increases in perfusion pressure. This autoreversal of bradykinin response tentatively was explained on the basis of known effects of bradykinin on prostaglandin synthesis with specific reference to PGF2 alpha.

Animals↗
PubMed2001

[The isolated perfused rat pancreas - an experimental model for investigation the early events in the pathogenesis of acute pancreatitis].

METHODS: External perfusions of the pancreatic glands of Wistar-rats were done, using a modified Krebs-Ringer-Buffer (KRB). We looked for an elevation of amylase, lipase and lactate-dehydrogenase in the effusion fluid (portal outflow fluid). We investigated a normal perfusion (KRB, 60 minutes), a long term perfusion (KRB, 240 minutes) and a perfusion (60 minutes) including an additive of the detergents triton x-100 or the cholecystokinin analogue ceruletid (10(-8) M). RESULTS: An isolated external perfusion of a rat pancreas is possible without inducing any increase of parameters of damage such as amylase, lipase or lactate-dehydrogenase in the outflow medium. The perfusion time should be limited to 80 minutes including a 20 minutes equilibration period. A damage of pancreatic parenchyma is indicated by increased levels of pancreatic enzymes in the perfusion medium. Such damage can be induced by various noxious substances like detergents or cerulein, which has a significance in the pathophysiology of experimental acute pancreatitis. A significant increase (p < 0.01) of lactate-dehydrogenase, lipase and amylase was found 10, 20 and 30 minutes after an application of triton x-100. During a perfusion with the cholecystokinin analogue ceruletid (10(-8) M) we found an increase of lipase (p < 0.05) after 30 minutes and an increase of amylase (p < 0.05) after 50 minutes perfusion. CONCLUSIONS: The isolated perfused rat pancreas is a valuable experimental model to investigate the early phase of pathophysiology in acute pancreatitis.

Acute Disease↗
PubMed1987

The conversion of atrial natriuretic peptide (ANP)-(1-126) to ANP-(99-126) by rat serum: contribution to ANP cleavage in isolated perfused rat hearts.

Atrial myocytes cultured for 7 days in serum-free medium secrete a 15K form of atrial natriuretic peptide (15K ANP), but isolated perfused rat hearts secrete the major circulating form of the hormone, a 3K peptide, 3K ANP. This difference was examined in the present study. 15K ANP was purified from rat atria, and sequencing analysis demonstrated that this atrial-derived ANP possessed an NH2-terminal sequence identical to that of pro-ANP; this is consistent with other reports suggesting that the major form of ANP in the atria is ANP-(1-126). Fresh rat serum was shown to cleave efficiently ANP-(1-126) to form a 3K immunoactive ANP-related peptide. Upon purification and sequencing the identity of this peptide was confirmed as ANP-(99-126); ANP-(99-126) was relatively resistant to further proteolysis by rat serum. To probe further the specificity of the serum conversion, synthetic ANP-(92-126) was used as a substrate; purification and sequencing of the immunoactive product peptide verified its identity as ANP-(99-126). Since purified thrombin and plasma kallikrein both cleaved ANP-(1-126) to 3K ANP-like material, inhibitors of these enzymes were tested for their ability to inhibit the serum cleavage of ANP-(1-126). D-Phe-Phe-Arg-Chloromethylketone (D-Phe-Phe-Arg-CMK) and D-Phe-Pro-Arg-CMK both inhibited serum ANP cleavage by over 90% at low micromolar concentration. When these inhibitors were added to the isolated heart perfusate, 3K ANP was still released by the atria, indicating that ANP processing occurs in the heart in a region not accessible to the inhibitors (i.e. intracellularly) or that the ANP-processing enzyme(s) is not inhibited by these CMK analogs and is, therefore, not related to serum-derived proteases.

Amino Acid Sequence↗
PubMed2001

Inhibition of lung phosphodiesterase improves responsiveness to inhaled nitric oxide in isolated-perfused lungs from rats challenged with endotoxin.

OBJECTIVES: To investigate the ability of phosphodiesterase (PDE) selective inhibitors to improve responsiveness to inhaled nitric oxide (NO) in isolated-perfused lungs of rats pretreated with endotoxin/lipopolysaccharide (LPS). DESIGN AND SETTING: Prospective, controlled animal study in the animal research facility of a university hospital. INTERVENTIONS: Sixteen hours after adult Sprague-Dawley rats were injected intraperitoneally with 0.4 mg/ kg E. coli 0111:B4 LPS administration, lungs were isolated and perfused, and the thromboxane mimetic U46619 was employed to increase the mean pulmonary artery pressure by 5-7 mmHg. The lungs were then ventilated with or without 0.4 ppm NO, and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA; PDE type 2 inhibitor), milrinone (PDE type 3 inhibitor), or zaprinast (inhibitor of PDE types 5 and 9) were added to the perfusate. MEASUREMENTS AND RESULTS: In the presence of EHNA (12.5, 25, 50 microM) the vasodilator response to inhaled NO was not greater than in its absence (0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg vs. 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg, respectively). In the presence of milrinone (125, 250, 500 nM), the vasodilator response to inhaled NO was also not improved. In contrast, zaprinast (3.7, 7.4, 14.8 microM) augmented the pulmonary vasodilatory effect of inhaled NO in lungs from LPS-pretreated rats from 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg to 0.75 +/- 0.25, 1.5 +/- 0.5, 1.75 +/- 0.75 mmHg, respectively (p < 0.05). CONCLUSIONS: Our results demonstrate that inhibition of pulmonary PDE enzyme activity with zaprinast increases vasodilator responsiveness to inhaled NO in lungs obtained from rats 16 h after LPS challenge.

Animals↗
PubMed1994

The effects of dihydralazine, labetalol and magnesium sulphate on the isolated, perfused human placental cotyledon.

OBJECTIVE: To assess the effects of dihydralazine, labetalol and magnesium sulphate on the vascular tone in the isolated, perfused human placental cotyledon. METHODS: In vitro perfusion of the fetal compartment of isolated, human placental cotyledons. RESULTS: None of the drugs affected basal vascular tone. The thromboxane A2-mimic U46619 and endothelin-1 induced a concentration-dependent increment in perfusion pressure, while 5-hydroxytryptamine induced a variable increase, and norepinephrine induced a small, transient increase in perfusion pressure. After preconstriction with U46619, magnesium sulphate (1.5 x 10(-3) to 6 x 10(-3) mol/l) induced a decrease in perfusion pressure, while dihydralazine (10(-6) to 10(-4) mol/l) or labetalol (10(-7) to 10(-4) mol/l) enhanced the perfusion pressure. These effects of dihydralazine and labetalol were unaffected by treatment with indomethacin 10(-6) mol/l, but could be reversed by addition of magnesium sulphate 6 x 10(-3) mol/l. Labetalol 10(-6) to 10(-4) mol/l also caused an increase in the perfusion pressure induced by endothelin-1, but showed no effects after preconstriction with 5-hydroxytryptamine. Pretreatment with labetalol 10(-4) mol/l inhibited the transient increase in perfusion pressure induced by norepinephrine 3 x 10(-5) mol/l. CONCLUSIONS: The present data demonstrated that the commonly used vasodilating agents labetalol and dihydralazine do not produce vasodilatation in the human perfused cotyledon after vasoconstriction induced by agents of suggested importance for maintenance of fetal placental vascular tone, and that high concentrations of these drugs may even enhance vasoconstriction induced by thromboxane and endothelin-1 in this area. Magnesium sulphate may show the potential to reverse such unwanted effects of dihydralazine and labetalol.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1987

L-platelet activating factor induces changes on renal vascular resistance, vascular reactivity, and renin release in the isolated perfused rat kidney.

Rat kidneys were isolated and perfused with a modified Krebs-Henseleit buffer containing 4% albumin. Perfusate recirculated except during L-platelet activating factor (L-PAF), angiotensin II (ang II), and norepinephrine (NE) infusions. L-PAF caused a dose-dependent decrease in renovascular resistance (RVR): -6 +/- 3% at 10(-9)M, -12 +/- 6% at 10(-8)M, -18 +/- 3% at 10(-7) and -20 +/- 7% at 10(-6)M. L-PAF increased immunoreactive PGE (iPGE) and thromboxane (iTXB) release into the venous effluent from 2.4 +/- 0.2 to 3.9 +/- 0.4 ng/min (p less than 0.05) and from 2.1 +/- 0.4 to 3.5 +/- 0.5 ng/min (p less than 0.05), respectively. Vasodilation by L-PAF (10(-7) M) in the presence of indomethacin (INDO) (5 microM) was enhanced compared to the non-INDO response (RVR change: L-PAF = -18 +/- 3% vs. L-PAF = -26 +/- 3%; p less than 0.05). As a control for specificity, the was infused at 10(-9) M, 10(-8) M, and 10(-7) M. None of these concentrations changed renal vascular resistance. To study the vascular receptor responsible for L-PAF-induced vasodilation, dose-response curves to NE and ang II were established with and without L-PAF (10(-7) M). The NE dose-response curve was unchanged by L-PAF, whereas the ang II dose-response curve was shifted to the right by one order of magnitude. In kidneys pretreated with INDO (5 microM), the L-PAF-induced shift of the ang II dose-response relation was increased to 2-3 orders of magnitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1995

Measurement of nitric oxide release in the isolated perfused rat lung.

In this study we have continuously measured real-time production of nitric oxide (NO) in the isolated, perfused rat lung by using an NO monitor (model NO-501, Inter Medical Co., Nagoya, Japan) with an NO-selective resin microsensor. A stable NO response was obtained when the sensor was placed in the pulmonary artery or the pulmonary vein; in contrast, the tracings obtained from the lung periphery were unstable. Furthermore, the NO release was higher when the isolated lungs were perfused with physiological salt solution rather than whole blood perfusion. Changes in NO production were also monitored in acute hypoxia and reoxygenation. Pretreatment with endotoxin (10 mg/kg) potentiated the NO release observed, and this effect of endotoxin was further potentiated by arginine (1 x 10(-4) M) and acetylcholine (1 x 10(-5) M) and countered by the NO synthase inhibitor, L-NG-nitro-arginine methyl ester (L-NAME; 1 x 10(-3) M).

Animals↗
PubMed1994

Estrogen mediates the pregnancy-enhanced cardiotoxicity of cocaine in the isolated perfused rat heart.

OBJECTIVE: To determine whether pregnancy enhances cocaine toxicity in the isolated perfused whole rat heart model and whether this enhanced toxicity can be simulated by pre-treatment with either estrogen or progesterone. METHODS: Hearts excised from 65 female Sprague-Dawley rats were attached to a Langendorff apparatus for measurement of left ventricular systolic pressure, heart rate, and contractility. Before excision, the animals were assigned to one of five groups: 1) nonpregnant, 2) pregnant, 3) nonpregnant pretreated with progesterone, 4) nonpregnant pretreated with estrogen, and 5) nonpregnant pretreated with estrogen and progesterone. Each group was exposed serially to the following cocaine concentrations: 5 x 10(-6), 1 x 10(-5), and 6 x 10(-5) mol/L. RESULTS: Heart rate declined at all doses of cocaine (9.2, 6.9, and 31.0%, respectively). The lowest dose of cocaine had positive inotropic effects, with a 23.2% increase in left ventricular pressure and a 15.3% increase in contractility. Exposure to the two higher doses resulted in negative inotropic effects (a 24.8% decrease in left ventricular pressure and a 39.7% decrease in contractility for the highest dose). Although pre-treatment with estrogen, alone or with progesterone, resulted in responses similar to those seen in pregnant animals, progesterone pre-treatment alone failed to do so. CONCLUSIONS: Cocaine displayed cardiotoxicity in isolated rat hearts similar to that in other animal models. This toxicity was enhanced by pregnancy. We were able to simulate changes by pretreating the animals with estrogen. Perhaps the enhanced cardiotoxicity of cocaine in pregnancy is partially mediated by estrogen.

Animals↗
PubMed1982

Coronary vasoconstrictor and vasodilator actions of arachidonic acid in the isolated perfused heart of the rat.

The administration of arachidonic acid (AA) to the isolated perfused heart of the rat usually produced biphasic coronary responses characterized by initial vasoconstriction followed by prolonged vasodilatation. However, some responses were predominantly vasoconstrictor or vasodilator. The non-steroidal anti-inflammatory agents (NSAA) indomethacin (1-5 mg/l) and naproxen (12.5-25 mg/1) reversibly inhibited both phases of the response induced by AA. Pretreatment of animals with indomethacin (5 mg/kg) or naproxen (25 mg/kg) daily, resulted in unaltered coronary response to AA. Subsequent addition of NSAA to the perfusate produced inhibition of the AA effect. Short infusions of acetylsalicylic acid at low concentrations (2.9 micrograms/ml), dipyridamole (0.6 micrograms/ml) and sulphinpyrazone (28.7 micrograms/ml) selectively inhibited the vasoconstrictor phase of the response to AA. It was confirmed that metabolic coronary dilatation induced by cardiostimulation was inhibited by prolonged AA administration; this effect was prevented by NSAA pretreatment. Reactive hyperaemic responses to short lasting occlusions of coronary inflow were unaffected by NSAA. Linolenic, linoleic, dihomo-gamma-linolenic and oleic acid usually produced decreases in coronary flow which were unaffected by NSAA, dipyridamole or sulphinpyrazone. Intra-aortic injections of AA, prostacyclin (PGI2) and prostaglandin E2 (PGE2) in the intact rat produced a dose-dependent decrease in blood pressure with the AA response inhibited by indomethacin. PGI2 and PGE2 produced long lasting coronary vasodilatation in the isolated heart. The coronary actions of AA appear to be due to its transformation, within the easily accessible vascular wall, into prostaglandin and thromboxane-like substances. We suggest that a vasoconstrictor thromboxane A2-like substance may be responsible for coronary vasospasm. Coronary insufficiency may also result from an inhibition of compensatory metabolic coronary dilatation by increased synthesis of PGE2 within the myocardial cell.

Animals↗
PubMed2001

Blood flow rate and energy charge in the isolated perfused canine liver.

Background. Liver viability depends on blood flow rate, which varies among isolated perfused livers used in different studies. We aimed to identify the minimal blood flow capable of keeping the energy charge compatible with liver viability. Materials and methods. Isolated canine livers were assigned to different groups (n = 4) with blood flow rates of 0.5 (Group I), 1.0 (Group II), and 1.5 ml/g/min (Group III). Blood gases, hematocrit, and glucose were measured over 180 min. Nucleotides, serum osmolarity, and electrolytes were also measured. Morphological changes were recorded at the end of each experiment. Results. Acid-base balance was better in livers from Group III. Electrolytes, osmolarity, hematocrit, and glucose showed no differences. Higher energy charges correlated with higher blood flow rates. On histopathology, there was evidence of more hydrostatic pressure-related changes in Group III, with no difference in necrosis or inflammatory-related alterations. Conclusions. (1) Energy charge correlates strongly with blood flow rate. (2) A rate of 1.5 ml/g/min allows for a better electrolyte, osmolarity, and acid-base balance. (3) Morphological analysis is not a sensitive predictor of organ viability as assessed by energetic potential. (4) The minimal blood flow rate required to attain an energy charge above 0.75 is 1.33 ml/g/min.

Acid-Base Equilibrium↗
PubMed1992

Hepatic glutathione concentrations and the release of pyrrolic metabolites of the pyrrolizidine alkaloid, monocrotaline, from the isolated perfused liver.

We have examined the relationship between the metabolism of the pyrrolizidine alkaloid, monocrotaline, and glutathione concentration in the isolated, perfused rat liver. On perfusion of monocrotaline (300 microM) through the isolated liver, high concentrations (1.1 mM) of its metabolite glutathionyldehydroretronecine are released into bile, while much lower amounts (4.86 microM; 0.05 mumol/g liver) accumulate in the perfusate over a 1 hr perfusion period. Metabolite concentration in both the bile and perfusate increase when the level of monocrotaline perfused is increased to 900 microM. Metabolite release is also elevated in livers pretreated with phenobarbital. Monocrotaline perfusion lowered glutathione concentrations in the liver from 30 min onwards. Livers from animals treated with buthionine sulfoximine or chloroethanol showed much lower glutathione levels after 60 min perfusion. Livers from chloroethanol-treated (but not buthionine sulfoximine-treated) animals showed significantly lower release of pyrroles into the bile on perfusion with monocrotaline, but there is no effect on the rate of build-up of pyrrolic metabolites in the perfusate. We conclude that hepatic glutathione concentrations and the release of pyrrolic metabolites of monocrotaline mutually interact. Exposure of the liver to monocrotaline reduces glutathione concentrations, while marked depletion of liver glutathione concentration leads to a decrease in the release of monocrotaline metabolites.

Animals↗
PubMed2006

The isolated perfused rat liver: standardization of a time-honoured model.

For many years, the isolated perfused rat liver (IPRL) model has been used to investigate the physiology and pathophysiology of the rat liver. This in vitro model provides the opportunity to assess cellular injury and liver function in an isolated setting. This review offers an update of recent developments regarding the IPRL set-up as well as the viability parameters that are used, with regards to liver preservation and ischaemia and reperfusion mechanisms.A review of the literature was performed into studies regarding liver preservation or liver ischaemia and reperfusion. An overview of the literature is given with particular emphasis on perfusate type and volume, reperfusion pressure, flow, temperature, duration of perfusion, oxygenation and on applicable viability parameters (liver damage and function). The choice of IPRL set-up depends on the question examined and on the parameters of interest. A standard technique is cannulation of the portal vein, bile duct and caval vein with pressure-controlled perfusion at 20 cm H2O (15 mmHg) to reach a perfusion flow of approximately 3 mL/min/g liver weight. The preferred perfusion solution is Krebs-Henseleit buffer, without albumin. The usual volume is 150-300 cm3, oxygenated to a pO2 of more than 500 mmHg. The temperature of the perfusate is maintained at 37 degrees C. Standardized markers should be used to allow comparison with other experiments.

Animals↗
PubMed1983

Metabolism of isosorbide dinitrate in the isolated perfused rabbit lung.

The uptake and metabolism of isosorbide dinitrate was investigated in the recirculating isolated perfused rabbit lung and in lung homogenate 9000 X g supernatant. Concentration versus time profiles from the isolated lung experiments indicate rapid metabolism of isosorbide dinitrate and corresponding increases in the metabolites 5-isosorbide mononitrate, 2-isosorbide mononitrate, and isosorbide. The data suggest that the mononitrates formed in the lung tissue were converted to isosorbide at an extraordinarily high rate. Surprisingly, the rate of appearance of completely denitrated isosorbide was greater when isosorbide dinitrate was administered to the lung than when the mononitrate metabolites of isosorbide dinitrate were administered. The results suggest rapid metabolism of a substantial portion of the mononitrates formed endogenously from isosorbide dinitrate before partitioning of mononitrates into the perfusion medium could occur. The metabolism of isosorbide dinitrate in lung homogenate 9000 X g supernatant exhibited a metabolic scheme kinetically different from the intact lung studies, as isosorbide was formed slowly from a mononitrate intermediate and not by a near-simultaneous cleavage of both nitrate ester groups. Intravascular multiple-dose studies did not demonstrate any inhibition between isosorbide dinitrate and the mononitrates.

Animals↗
PubMed1990

Norepinephrine-induced cholestasis in the isolated perfused rat liver is secondary to its hemodynamic effects.

In this study we examined the effect of pharmacological doses of various alpha-adrenergic agents on hepatic portal perfusion, organic anion uptake and bile secretion using the isolated perfused rat liver. Addition of norepinephrine at portal perfusate concentrations ranging from 0.01 to 100 mumol/L induced a dose-related increase in portal pressure with a twofold increment at the highest concentration. This was accompanied by an inhibition of hepatocellular uptake of taurocholate by 16.8% +/- 1.8% and of sulfobromophthalein (BSP) by 32.9% +/- 3.0% compared with controls. Moreover, a 22.5% +/- 3% decrease in bile flow rate and a 22.8% +/- 4% inhibition of biliary excretion of taurocholate were observed. Addition of other alpha-adrenergic agonist (epinephrine, dopamine and phenylephrine) at similar concentrations produced the same hepatic effects as observed with norepinephrine. During infusion of these alpha-adrenergic agents, trypan blue infusion revealed a patchy perfusion pattern of the liver surface compared with the homogeneously stained organs in controls. The hemodynamic alterations could be confirmed by electron microscopy examination that demonstrated that increased portal pressure produced by norepinephrine was associated with sinusoidal shunting. All hemodynamic, metabolic and biliary changes induced by norepinephrine could be entirely prevented by concomitant infusion of the alpha-antagonist phentolamine, thus indicating that norepinephrine-induced hepatic effects were mediated by alpha-receptors. In contrast, simultaneous addition of papaverine, an unspecific vasodilator, prevented the hemodynamic and the biliary changes of norepinephrine, but failed to modify the metabolic effects of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Phospholipase A2-induced lung edema and its mechanism in isolated perfused guinea pig lung.

Lung injury induced by phospholipase A2 (PLA2, 0.046 IU/ml perfusate) was studied in a continuous weighing system of isolated perfused guinea pig lungs. The results revealed that lung weight increased progressively during the 30-min perfusion of PLA2. No change of pulmonary arterial pressure was observed in the same period. Albumin permeability-surface area product, lung index, lung water content, exudate from pleura, and angiotensin-converting-enzyme activity increased significantly at the end of 30 min PLA2 perfusion. p-Bromophenacyl bromide, a PLA2 inhibitor, may block the above changes nearly completely. The effects of inhibitors of cyclooxygenase (indomethacin, IM), lipoxygenase (diethylcarbamaxine, DE), and platelet-activating factor (SRI 63-441) on PLA2-induced lung injury were also studied. We found: (1) PLA2 may induce high permeability lung edema. The role of endothelial injury in the permeability change remains to be further investigated. (2) DE ameliorated lung injury significantly within 10 min of PLA2 treatment but showed no effect after 15 min. IM ameliorated lung injury during the whole experimental period. SRI 63-441 had no effect. It is suggested that PLA2 may damage lung by inducing products of cyclooxygenase and lipoxygenase besides its direct effect.

Acetylcholinesterase↗
PubMed2005

Decreasing the oxidant stress from paraquat in isolated perfused rat lung using captopril and niacin.

The abilities of captopril and niacin to protect against the lung toxicity of paraquat (PQ) were studied. The anti-oxidative action of captopril, an angiotensin-converting enzyme inhibitor, appears to be attributable to the sulphahydryl group (SH) in the compound, which gives captopril the ability to scavenge reactive oxygen species. Niacin replenishes the NAD and ATP depletion caused by reactive oxygen species. PQ causes lung damage in man and in several species of laboratory animals. The damage is initially manifested by hemorrhage and edema, and later by consolidation of the lung and fibrosis development. In this study, the lungs of male Wistar rats (250-300 g in weight) were perfused by Krebs-Ringer buffer alone (control), niacin (150 microM), captopril (10 microM) and PQ (600 microM) in perfusion fluid, and the biochemical changes that occurred in isolated rat lung were examined within 1 h and compared to PQ alone. The results show that captopril significantly decreases the lung weight/body weight ratio when used as a pretreatment and a post-treatment to captopril (p<0.0001). The results also show that captopril (10 microM) and niacin (150 microM) significantly decreases PQ-induced lung toxicity. Lactate dehydrogenase (LDH) activity significantly decreased in treatment groups as compared to the PQ group (p<0.0001). This study suggests that paraquat causes increased lipid peroxidation and LDH activity and decreased glutathione (GSH) and total protein in isolated perfused rat lung. These effects are reduced under these experimental conditions by captopril and niacin.

Animals↗
PubMed1984

The effect of in vivo hyperoxic exposure on the release of endogenous histamine from the rat isolated perfused lung.

Female rats were exposed to either 1 atm air or 100% O2 for 12, 24, or 48 hr. The rats were killed, the lungs were removed, and an isolated perfused lung (IPL) system was prepared. The isolated lung preparation was perfused with a modified Krebs-Henseleit buffer in a recirculating system, and the effect of the O2 exposures on histamine release from the IPL was determined. The effect of these O2 exposures on malondialdehyde formation in the IPL also was examined. Maximal release of histamine occurred after 20 min of perfusion. A linear relationship was found between the maximal histamine concentration released into the perfusate and the length of time the rats were exposed to normobaric hyperoxia. Malondialdehyde in lung perfusate also increased in a linear manner with increasing O2 exposure time. Addition of the H1-receptor antagonist, d-chlorpheniramine, to the perfusate completely inhibited basal histamine release from the IPL of both air- and O2-exposed rats, while addition of the H2-receptor antagonist, metamide, potentiated the release process. There was no significant effect demonstrated when an equimolar concentration of atropine was added to the perfusate. Arterial plasma histamine from rats exposed to 100% O2 for 24 hr increased 40% when compared to air-exposed controls, while histamine release from the IPL increased 75%. In conclusion, exposure of rats to normobaric hyperoxia caused both histamine release and malondialdehyde formation. Histamine release probably occurred as a result of a free radical-induced peroxidation of the lipid membrane of histamine-containing mast cells. Release of histamine from the IPL may be an early biochemical marker of damage by O2.

Animals↗
PubMed1986

Urea synthesis and CO2/HCO3- compartmentation in isolated perfused rat liver.

With physiological portal HCO3- and CO2 concentrations of 25mM and 1.2mM in the perfusate, respectively, acetazolamide inhibited urea synthesis from NH4Cl in isolated perfused rat liver by 50-60%, whereas urea synthesis from glutamine was inhibited by only 10-15%. A decreased sensitivity of urea synthesis from glutamine to acetazolamide inhibition was also observed when the extracellular HCO3- and CO2 concentrations were varied from 0-50mM and 0-2.4mM, respectively. Stimulation of intramitochondrial CO2 formation at pyruvate dehydrogenase with high pyruvate concentrations (7mM) was without effect on the acetazolamide sensitivity of urea synthesis from NH4Cl. Urea synthesis was studied under conditions of a limiting HCO3- supply for carbamoyl-phosphate synthesis. In the absence of externally added HCO3- or CO2, when 14CO2 was provided intracellularly by [U-14C]glutamine or [1-14C]-glutamine oxidation, acetazolamide had almost no effect on label incorporation into urea, whereas label incorporation from an added tracer H14CO3- dose was inhibited by about 70%. 14CO2 production from [U-14C]glutamine was about twice as high as from [1-14C]glutamine, indicating that about 50% of the CO2 produced from glutamine is formed at 2-oxoglutarate dehydrogenase. The fractional incorporation of 14CO2 into urea was about 13% with [1-14C]-as well as with [U-14C]glutamine. Addition of small concentrations of HCO3- (1.2mM) to the perfusate increased urea synthesis from glutamine by about 70%. This stimulation of urea synthesis was fully abolished by acetazolamide. The carbonate-dehydratase inhibitor prevented the incorporation of added HCO3- into urea, whereas incorporation of CO2 derived from glutamine degradation was unaffected. Without HCO3- and CO2 in the perfusion medium, when 14CO2 was provided by [1-14C]-pyruvate oxidation, acetazolamide inhibited urea synthesis from NH4Cl as well as 14C incorporation into urea by about 50%. Therefore carbonate-dehydratase activity is required for the utilization of extracellular CO2 or pyruvate-dehydrogenase-derived CO2 for urea synthesis, but not for CO2 derived from glutamine oxidation. This is further evidence for a special role of glutamine as substrate for urea synthesis.

Ammonium Chloride↗