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PubMed1979

Effect of oleic acid on insulin secretion by the isolated perfused rat pancreas.

The isolated perfused rat pancreas was utilized to investigate the effect of oleic acid on insulin secretion. In the absence of glucose, a continuous infusion of oleic acid (1500 micromol/l) induced a biphasic insulin release. This effect was reduced at low extracellular calcium concentration. In the presence of oleic acid 1500 micromol/l, the insulin response to 10 mmol/l arginine occurred earlier, the total amount of insulin released in response to the amino acid being unchanged. Such an effect was not obtained when oleic acid in the medium was 750 micromol/l, but it was observed in the presence of oleic acid 1500 micromol/l when the concentration of albumin in the perfusate was increased from 2 g/100 ml to 4 g/100 ml. The insulin response to a continuous infusion of glucose (4.4 mmol/l and 16.7 mmol/l) was potentiated by the presence of oleic acid 1500 micromol/l in the perfusate. No modification of the biphasic pattern of insulin response to glucose 16.7 mmol/l was observed. These results demonstrate that high concentrations of oleic acid stimulate insulin release from the isolated perfused rat pancreas and modulate the insulin response to arginine or glucose.

Animals↗

PubMed1999

Multiple quantum filtered 23Na NMR spectroscopy of the isolated, perfused rat liver.

Isolated, perfused rat livers were examined by single-quantum (SQ) and double-quantum-filtered (DQ-filtered) 23Na spectroscopy during prolonged global ischemia and during perfusion with ouabain, low-buffer potassium, or lithium-enriched buffer. Baseline separation of the intracellular (Na(i)+) and extracellular (Na(e)+) sodium resonances using TmDOTP5- allowed a direct comparison of temporal changes in SQ versus DQ-filtered Na(i)+. The SQ Na(i)+ signal increased approximately 150% during the first 15 min of global ischemia and then remained relatively constant over the next 45 min, while the DQ-filtered signal steadily increased approximately 400% over the same 60 min period. In similar experiments in which all perfusate sodium was replaced by lithium, the DQ-filtered Na(i)+ signal increased approximately 180% over a similar period of ischemia. Exposure of livers to ouabain also resulted in larger increases in DQ-filtered versus SQ signal of Na(i)+. The approximately 290% increase in DQ-filtered sodium observed during perfusion of livers with a hypokalemic buffer (1.2 mM K+) could be completely reversed by continued perfusion with a buffer containing normal levels of K+ (4.7 mM). These data suggest that the DQ-filtered Na(i)+ signal of liver does not simply report an increase in [Na(i)+], but may be exquisitely sensitive to other intracellular events initiated by altered physiology.

Animals↗

PubMed1989

Effect of hypoxia on endothelial morphology and interendothelial junctions in the isolated perfused rat heart.

Isolated perfused rat hearts were used to assess the effect of 30 or 60 mins of hypoxia on the ultrastructure of the capillary endothelium and particularly on the interendothelial junctions. Perfusions were carried out both in the presence and absence of albumin. Albumin had no effect on ultrastructure or membrane spacing in the interendothelial clefts, neither in oxygenated controls nor in hypoxic hearts. After 30 and 60 mins of hypoxia some capillaries showed endothelial swelling while after 60 mins the endothelium of others was attenuated. The wide regions of the intercellular cleft were not affected by hypoxia but the "narrow zone" gap between membranes became significantly smaller. We conclude that factors within the clefts other than the "tightness" of the narrow zones are responsible for changes in permeability in hypoxia and with albumin.

Animals↗

PubMed1987

Renal anaphylaxis. I. Antigen-initiated responses from isolated perfused rat kidney.

Isolated perfused rat kidneys were passively sensitized by addition of either mouse ascitic fluid containing monoclonal IgE against dinitrophenol (DNP) or DNP-specific purified IgE. After washing the organ, defined doses of DNP-bovine serum albumin were given as bolus injection via the kidney artery. Antigen challenge of IgE-sensitized kidneys resulted in a dose-dependent increase of perfusion pressure starting with 5 micrograms antigen (2.46 +/- 0.2 mm Hg) and reaching a maximum at dose higher than 100 micrograms (10.3 +/- 1.6 mm Hg) (N = 4, means +/- 1 SD). A decrease of glomerular filtration rate was also observed which reached a plateau at 100 micrograms antigen (-68.5 +/- 2.9%) (N = 4). Regardless of the dose of antigen used, the urinary protein excretion markedly increased for the first five minutes following antigen injection and returned to basal values after 10 minutes. The total amounts of histamine, PGE2 and paf-acether (platelet-activating factor) released upon antigen challenge (1 mg) for 15 minutes reached maximal values of 405 +/- 21.1 ng, 286 +/- 19.4 pg and 12.3 +/- 3.2 ng (N = 5), respectively. None of these hemodynamic and biochemical effects were observed using IgG1 monoclonal antibodies or when the ascitic fluid containing monoclonal IgE used to sensitize the organ was heated at 56 degrees C for two hours. Thus, we have described a pure IgE-dependent rat kidney anaphylaxis. Antigen challenge markedly altered renal parameters and triggered the release of various mediators from the organ, suggesting that type I-hypersensitivity reactions may play a role in renal pathophysiology.

Anaphylaxis↗

PubMed1992

Pressure dependent modulation of renin release in isolated perfused glomeruli.

The isolated perfused glomerulus technique was used to study pressure dependence of renin release in single, microdissected rabbit glomeruli with intact afferent arteriole and intact Bowman's capsule. Renin release from individual afferent-glomerular units was measured in 30 minute intervals while afferent arteriolar pressure was either decreased from 55 to 40 to 25 mm Hg or increased from 25 to 40 to 55 mm Hg. There was a clear, inverse relation of renin release and afferent pressure. Mean renin release rate was 3.2 times higher at 25 than at 55 mm Hg and 1.5 times higher at 40 than at 55 mm Hg. To evaluate the possible role of wall stretch in mediating this response, inner and outer afferent arteriolar diameters were measured by videomicroscopy. Outer afferent diameter remained constant between 25 and 55 mm Hg, whereas inner diameter exhibited a slight increase. Changes of afferent arteriolar wall stretch, however, did not correlate with changes of renin release. These data for the first time directly demonstrate the existence of a renin baroceptor at the level of the renal afferent arteriole. They furthermore suggest that this baroceptor is not a stretch receptor.

Animals↗

PubMed1983

Effect of taurochenodeoxycholate or tauroursodeoxycholate upon biliary output of phospholipids and plasma-membrane enzymes, and the extent of cell damage, in isolated perfused rat livers.

Isolated perfused rat livers were used to study the effects of taurochenodeoxycholate (TCDC) and tauroursodeoxycholate (TUDC) upon some aspects of biliary composition. After depletion of the endogenous bile salt pool of the liver, introduction of either bile salt brought about increases in bile flow, bile salt output and biliary phospholipid output. Taurochenodeoxycholate needed a lower biliary concentration to produce phospholipid output than did tauroursodeoxycholate. TCDC perfusion caused a substantial output of plasma-membrane enzymes (5'-nucleotidase and alkaline phosphodiesterase) into the bile, whereas TUDC caused little output of either enzyme; this may represent a characteristic difference between the effects of the two bile salts on the hepatobiliary system. The results from TUDC perfusion indicate also that much of the output of biliary phospholipid promoted by bile salts, may be independent of the output of plasma-membrane enzymes promoted by bile salts.

5'-Nucleotidase↗

PubMed1985

Metabolism of glycine- and hydroxyproline-containing peptides by the isolated perfused rat kidney.

Isolated perfused rat kidneys removed considerable quantities of glycyltyrosine, glycylhydroxyproline, tetraglycine and prolylhydroxyproline from the perfusate. The component amino acids are released into the perfusate and, in the case of the glycine-containing peptides, there is increased synthesis of serine. Removal of peptides was more than could be accounted for on the basis of filtration, so antiluminal metabolism is indicated. Metabolism of such peptides by the kidney may contribute to renal serine synthesis in vivo.

Amino Acids↗

PubMed1986

Effects of enflurane and halothane on carbohydrate metabolism in isolated perfused rabbit lungs.

Isolated, perfused rabbit lungs were used to investigate the effects of enflurane and halothane on pulmonary carbohydrate metabolism. The development of oedema in the preparation was assessed by continuous measurement of pulmonary artery pressure, airway pressure and lung weight. Ventilation of the lungs with 2% enflurane for 3 h had no effect on the rates of glucose utilization and lactate production and there were only small changes in the indices of oedema. Likewise, ventilation with 1% halothane for 1 h had no effect on the rates of glucose utilization and lactate production, and did not change significantly the concentrations of glycogen, glucose, glycolytic intermediates and high-energy phosphate compounds in lung tissue. Enflurane and halothane, at clinically relevant concentrations, probably do not influence carbohydrate metabolism in the lung.

Animals↗

PubMed1983

Role of acetaldehyde and acetate in the development of ethanol-induced cardiac lipidosis, studied in isolated perfused rat hearts.

Isolated perfused rat hearts were used to study the effects of ethanol, acetaldehyde, and acetate on the cellular redox state and fatty acid metabolism in the myocardium. Ethanol had negligible effects on the cellular redox state but at high concentrations depressed the contractile activity and thereby secondarily the oxygen consumption. Acetaldehyde in concentrations below 50 microM had negligible effects on the redox state of the mitochondrial free NAD+/NADH couple, as studied by surface fluorometry of flavins and nicotinamide nucleotides. A reduction of NAD+ was observed with concentrations between 50 and 500 microM, while in the range of 0.5-1 mM the effect was biphasic, i.e., an initial reduction was followed by oxidation concomitantly with an increase in heart rate and peak systolic pressure. Acetate in millimolar concentrations caused in the coronary flow. A mitochondrial acetaldehyde dehydrogenase was revealed in the myocardium, having an apparent Km of 1.1 microM for acetaldehyde. Acetaldehyde in 50-microM concentration had no major effects on the uptake, oxidation, or lipid incorporation of oleate in the myocardium. Acetate in concentrations less than 2 mM did not affect the uptake of oleate into the myocardium, but did inhibit is oxidation and enhance its incorporation into tissue lipids in a dose-dependent manner. 2 mM acetate caused a 91% increase in oleate incorporation into tissue lipids over 30 min. The data can be interpreted as showing that acetaldehyde and acetate, the metabolites of ethanol, have metabolic effects on the myocardium, but only those of acetate are significant in concentrations encountered during ethanol oxidation in vivo. It is probable that acetate is involved in the development of ethanol-induced myocardial lipidosis, inhibiting the oxidation of fatty acids, and channelling them into the esterification pathway.

Acetaldehyde↗

PubMed1992

Effect of antioxidants on hypoxia/reoxygenation-induced injury in isolated perfused rat liver.

Isolated perfused livers from rats fasted overnight were subjected to 30 min. of hypoxia followed by reoxygenation for 60 min., resulting in marked cytotoxicity as evidenced by an enhanced release of cytosolic enzymes (lactate dehydrogenase: 14-fold over controls, glutamate-pyruvate-transaminase: 12-fold over controls) and glutathione (twofold over controls) into the perfusate, by calcium accumulation (by a factor of 1.4) in the tissue and by an 80% inhibition of bile secretion. Virtually no mitochondrial injury became apparent and no evidence for lipid peroxidation could be found. In the presence of ascorbate, an augmentation of hepatic injury was observed. This might be due to the pro-oxidant activity of ascorbate in the presence of ionized iron, which is easily released from high molecular weight stores under reductive (e.g. hypoxic) conditions. The water soluble vitamin E analogue trolox C as well as propyl gallate clearly protected the liver against hypoxia/reoxygenation injury, yielding further evidence for a causative role of oxidative stress in this model. Due to their water solubility and their high efficacy as free radical scavengers, these antioxidants might be of therapeutic value.

Animals↗

PubMed1968

Rhodopsin photoproducts: effects on electroretinogram sensitivity in isolated perfused rat retina.

Isolated perfused retinas of albino rats were exposed to brief saturating flashes of white light which bleached about 50 percent of the rhodopsin present. Transient photoproducts of the reaction could be detected for about 30 minutes. The b-wave threshold increased by some 3 logarithmic units immediately after the flash and remained stable at this level thereafter. This suggests that the longer-lived intermediate products of rhodopsin photolysis do not influence scotopic visual sensitivity.

Animals↗

PubMed1998

Dual mode of action of glucose pentaacetates on hormonal secretion from the isolated perfused rat pancreas.

Isolated perfused rat pancreases were exposed, in the presence of 10. 0 mM L-leucine, to either alpha-D-glucose pentaacetate, beta-L-glucose pentaacetate, or unesterified D-glucose, all tested at a 1.7 mM concentration. The pentaacetate ester of alpha-D-glucose and, to a lesser extent, that of beta-L-glucose stimulated both insulin and somatostatin release, whereas unesterified D-glucose failed to do so. In the case of insulin output, the two esters differed from one another not solely by the magnitude of the secretory response but also by its time course and reversibility. Compared with these data, the most salient difference found in the case of somatostatin release consisted of the absence of an early secretory peak in response to alpha-D-glucose pentaacetate administration and the higher paired ratio between the secretory responses evoked by the esters of glucose and by unesterified D-glucose (5.5 mM) administered at the end of the experiments. The two esters provoked an initial and short-lived stimulation of glucagon secretion, in sharp contrast to the immediate inhibitory action of unesterified D-glucose. Thereafter, alpha-D-glucose pentaacetate, but not beta-L-glucose pentaacetate, caused inhibition of glucagon release, such an effect being reversed when the administration of the ester was halted. These findings indicate a dual mode of action of glucose pentaacetate esters on hormonal secretion from the endocrine pancreas. The intracellular hydrolysis of alpha-D-glucose pentaacetate and subsequent catabolism of its hexose moiety may contribute to the early peak-shaped insulin response to this ester, to the persistence of a positive secretory effect in B and D cells after cessation of its administration, and to the late inhibition of glucagon release. However, a direct effect of the esters themselves, by some as-of-yet unidentified coupling process, is postulated to account for the stimulation of insulin and somatostatin release by beta-L-glucose pentaacetate and for the initial enhancement of glucagon secretion provoked by both glucose esters.

Animals↗

PubMed1986

Handling of lysozyme in isolated perfused proximal tubules.

Isolated, perfused proximal tubules from rabbit were used to study the luminal endocytic uptake, digestion, and transcellular transport of 125I-lysozyme. Ten tubules were perfused for 20 min with 125I-lysozyme and [14C]inulin and then with tracer-free perfusate for additional 40 min before fixation. The uptake and digestion of lysozyme was calculated per millimeter tubule length. The transfer of intact lysozyme from perfusate to the bath was measured and compared with the transfer of inulin. Five tubules were processed for electron microscope autoradiography, and the grain distribution was analyzed quantitatively. The results show that 2.7% of the perfused amount of lysozyme was taken up, and 21.3% of the absorbed protein was digested. The present experiments demonstrate that the transfer of intact lysozyme from lumen to bath is not significantly different from the transfer of inulin. The autoradiographic analysis showed that lysozyme was localized mainly in endocytic vacuoles and lysosomes after 60 min of perfusion.

Animals↗

PubMedDate not supplied

Effects of low-dose hydrogen peroxide in the isolated perfused rat lung.

Isolated perfused rat lungs (IPRL) were used to determine if treatment with hydrogen peroxide would result in measurable changes in exhaled ethane during the early stages of capillary leak. Pulmonary capillary filtration coefficient, pulmonary vascular resistance, and dynamic pulmonary compliance were measured at two time points in an IPRL. Additionally, exhaled ethane was determined before and after the addition of 0.25 mM H2O2 to the perfusate in a second group of lungs. Lung wet/dry weight ratios were measured at the termination of the experiments. The ethane in the exhaled alveolar gas from IPRLs ventilated with 5%CO2/20%O2/balance N2 was quantitated using gas chromatography before and after the addition of 0.25 mM H2O2 to Krebs Ringer's 5% albumin perfusate. H2O2 (0.25 mM) caused a small but significant increase in capillary filtration coefficient from 0.0122 (+/- 0.0008) to 0.0173 (+/- 0.0013) mL/min/cm H2O/g dry lung weight (p < .05). Wet/dry lung weight ratios were increased in the H2O2-treated lungs (6.0654 +/- 0.1024 versus 5.4149 +/- 0.1143; p < .05). Exhaled ethane did not increase over the period of time hydrogen peroxide was present in the perfusate. In other experiments in closed-chested rats, 0.25 mM peroxide did not cause increased exhaled ethane, whereas 1 mM H2O2 did. This latter increase in ethane was not noted in similarly perfused open-chested rats. These data indicate that small amounts of H2O2 may increase pulmonary capillary permeability without affecting exhaled ethane measurements.

Animals↗

PubMed1976

Effect of fasting and insulin on the glucagon-induced orthophosphate incorporation to the isolated perfused rat liver.

Isolated perfused fed rat livers spontaneously liberated glucose and orthophosphate to the medium; 24-hr fasted rat livers did not exhibit these phenomena. In perfused fed rat livers, glucagon (2 mug) increased glucose output and promoted orthophosphate incorporation. In perfused fed rat livers, insulin (250 or 500 mU) inhibited the spontaneous liberation of glucose and orthophosphate. Comparable doses of insulin significantly reduced the glucagon (2 mug)-induced increase in glucose output from perfused fed rat liver, but did not affect orthophosphate uptake by the organ.

Animals↗

PubMed1976

Metabolism of environmental pollutants by the isolated perfused lung.

An isolated perfused rabbit lung system was developed for the study of pulmonary metabolism of foreign compounds. The main features of the system include the use of autologous whole blood, constant pressure perfusion, subatmospheric ventilation, and measurement of a variety of physiological and biochemical parameters. Pulmonary metabolism of benzo(a)pyrene has been investigated with this system. In addition to the 3-hydroxy metabolite, three dihydrodiols and an unidentified polar metabolite were also found. The polar metabolite accounted for approximately 50% of all metabolites found in the five compartments of the perfusion system. Pretreatment with 3-methylcholanthrene increased total metabolism of benzo(a)pyrene and shifted the pattern of metabolites. The perfusion system for the rabbit has been extensively modified for use with rats and guinea pigs. These smaller animals are currently being used to investigate pulmonary metabolism of trichloroethylene.

Animals↗

PubMed1980

Effect of labetalol on adrenoceptors in the isolated perfused rat mesentery.

Isolated perfused rat mesentery has been used to define alpha- and beta-adrenoceptors. Norepinephrine was used as a reference substance to induce vasoconstrictor responses (increase in perfusion pressure). Log-dose response curves were obtained in the dose range between 0.3-10 mug. Labetalol, a known competitive inhibitor of both alpha- and beta-adrenoceptors, when administered as a single bolus injection (3 mug) initially induced predominant alpha-blockade lasting upto 75 min followed by potentiation of the vasoconstrictor responses to norepinephrine used at multiple dose levels. This potentiation was maximum between 150-195 min after injection of labetalol. This potentiating effect of labetalol observed in the later phase of the experiment might be related to its inhibitory mechanism of neuronal uptake.

Animals↗

PubMed1988

An analysis of the components in UW solution using the isolated perfused rabbit liver.

The isolated perfused rabbit liver model has been used to determine the essential components of the UW solution for hepatic preservation by simple cold storage. Livers were stored on ice for 48 hr after initial flushing with the solution being tested, and then reperfused at 38 degrees C in an isolated perfusion circuit; bile flow and enzyme (SGOT, SGPT, and LDH) release during a 2-hr period were recorded. All solutions tested contained phosphate (25 mM) as a buffer and magnesium sulfate (5 mM). Sodium can be substituted for potassium without adverse effects. Lactobionate, raffinose and glutathione cannot be omitted; all other components can be eliminated without altering the effectiveness of the solution in this model.

Adenosine↗