Platelet-activating factor-induced microvascular dysfunction: role of adherent leukocytes

Platelet-activating factor (PAF) has been implicated in the pathogenesis of intestinal mucosal injury associated with endotoxemia, inflammation, allergic reactions, and ischemia-reperfusion. Although it is generally held that PAF initiates mucosal injury by enhancing transcapillary fluid and protein exchange, the effects of PAF on the intestinal microvasculature have not been defined to date. In this study we examined the influence of local intrarterial infusions of PAF (4, 20, and 40 ng/min) on intestinal transcapillary, lymphatic, and transmucosal water and protein fluxes. All of these parameters were increased by each of the concentrations of PAF. PAF caused a large rise in venous hematocrit without a corresponding increase in venous plasma protein concentration and a 14- to 37-fold increase in vascular protein flux. Local intra-arterial infusion of PAF promoted leukocyte adherence to mesenteric venular endothelium, a process that is inhibited by the monoclonal antibody, MoAb IB4. PAF-induced increments in intestinal lymph flow, venous hematocrit, and vascular protein flux were greatly attenuated in animals treated with MoAb IB4. The results of this study indicate that PAF promotes the filtration of fluid and protein across intestinal capillaries. These microvascular effects of PAF are mediated, in part, by adherent leukocytes.

[The role of the terminal amino acids in the physiological activity of opioid peptides (lymph stimulation and vascular permeability)]

The inclusion of amino acids (tyrosine, arginine) into the end part of the peptide chain permits to produce new analogues stimulating the lymph microvessels of the rat mesentery and increasing the blood microvessels permeability.

[Postoperative lymphotropic antibiotic therapy of urology patients with suppurative-septic complications]

Antibiotic treatment plays an important role in the prevention of pyoseptic complications of urologic surgery. However, conventional treatment results in irregular distribution of the antibiotic agent through the liquid media of the body, the emergence of resistant bacterial strains and lymphostasis, while higher doses increase toxic effect on the kidneys, aggravating the clinical condition. Treatment efficiency has been shown to be dependent on the effective dose of the drug in the inflammation focus, which is achieved through its endolymphatic administration. These techniques, however, are complicated and time-consuming. These shortcomings are avoided when lymphotropic antibiotic treatment (LAT), based on the combination of mechanical action on venous outflow and regional stimulation of lymphogenic absorption, using lymphostimulating effects of hemodilution and heparin, is administered. Some hemostatic parameters were examined in 49 patients (aged 50.4 +/- 7.4 years) following urologic operations. LAT was used in 28 of those. It is shown to provide a better antibiotic saturation of the lymphatic system, as compared to conventional treatment. LAT prevents postoperative pyoseptic complications, reduces 4 to 6-fold the consumption of antibacterial drugs and alleviates their urinary side-effects. Owing to its simplicity and effectiveness, the method can be recommended for wide-scale clinical application.

Lymphagogue and pulsatile activities of Daflon 500 mg on canine thoracic lymph duct

An earlier report proved that Daflon 500 mg constituted of 90% diosmin and 10% hesperidin exerts a lymphagogue effect on dogs. The aim of the present work is to investigate whether the lymphagogue effect of Daflon 500 mg is associated with an increase in pulsatile activity of lymphatic vessels. The investigation was carried out on mongrel dogs anaesthetised by pentobarbital (10 mg/kg); the lymph was collected by a fistula on the thoracic lymphatic duct; using this fistula the pulsatile activity of lymphatic vessels was estimated by Campbell and Health methodology. The lymphatic volume was measured every ten-minutes in graduated tubes for 2 hours and the pulsatile component of intralymphatic pressure (MPC) was estimated from measurements of the area (expressed in mm2) enclosed by the part of the tracing due to the pulsatile component during one minute. Daflon 500 mg was intravenously injected after having been dissolved in DMSO + TRIS; three doses were injected: 12.5, 6.25 and 3.125 mg/kg. Regarding the lymphagogue effect, Daflon 500 mg induced an increase in lymphatic flow correlated with the administered doses. The maximal 10-minute period lymphatic flows were 191% (12.5 mg/kg), 171% (6.25 mg/kg) and 91% (3.125 mg/kg); the peak of the effect was, in each case, reached between 20 and 25 minutes after the injection. Regarding the pulsatile activity, Daflon 500 mg induced an increase of MPC. The MPC was correlated with the increase in lymph flow (r = 0.877).

Further studies on the mechanism of inhibition of intestinal chylomicron transport by Pluronic L-81

This study explored further the hypothesis that intestinal cells have two pathways for producing large triacylglycerol-rich lipoprotein particles. The hydrophobic surfactant Pluronic L-81 (L-81) inhibits formation of chylomicrons (containing triacylglycerol synthesized from dietary fatty acids and monoacylglycerol, through the monoacylglycerol pathway), but not formation of very-low-density lipoproteins. L-81 does not inhibit lymphatic lipid transport during infusion of egg phosphatidylcholine, whose fatty acid is processed through the alpha-glycerol phosphate pathway and is transported in lymph in very-low-density lipoproteins. Thus, the first part of this study tested whether L-81 cannot inhibit the alpha-glycerol phosphate pathway, and thus L-81 can only affect chylomicron lipid secretion. Intestinal lymph fistula rats were infused with a lipid emulsion containing [1-14C]oleic acid, but no monoacylglycerol, to ensure that the oleic acid will be channeled to the alpha-glycerol phosphate pathway. Experimental rats received 1 mg/h of L-81 in their emulsion whereas control rats lacked L-81. Lymphatic triacylglycerol output, measured both chemically and radioactively, was markedly suppressed in the experimental rats as compared to the controls. Thus, these data indicate that the reason why lipid transport was unaffected by L-81 when egg phosphatidylcholine was infused was not because of the pathway used for the resynthesis of triacylglycerol from phosphatidylcholine. In the second part of this study, we measured the appearance time for chylomicron (in control rats) and for very-low-density lipoprotein (in L-81-treated rats). The appearance time is defined as the time between placement of radioactive fatty acid into the intestinal lumen and the appearance of radioactive lipid in the central lacteal. The average appearance time for the control rats was 10.8 min, which was significantly shorter than the 16.2 min in the L-81-treated experimental rats. This difference in appearance time further supports the hypothesis that chylomicron and very-low-density lipoprotein are packaged separately in the enterocytes and only the formation of chylomicron is inhibited by L-81.

[Effect of obsidan on lymph flow and lymphatic microvessels]

Life-time microscopy showed possible direct effects of obsidan on lymph vessels and flow in the experiment. With local application of the drug there was a short-term constriction, higher frequencies and lower amplitudes of lymphangionic pulsation; during its intramuscular injection, sustained dilator effects, two-phase shifts in the frequency and limitation of pulse amplitude were seen. With the two routes of obsidan administration heterogenous, unpersistent changes in the linear velocity of lymph flow were observed.

[Changes in the transsinusoidal fluid transfer in the cat liver during noradrenaline infusion]

The blood microcirculation and the lymph flow were studied in the cat hemodynamically isolated liver perfused under conditions of a regulated venous outflow and i.a. and intraportal administration of noradrenaline. An increase in the fluid transsinusoidal transfer revealed by the lymph flow acceleration in the liver, was determined by an increased hydrostatic pressure in the sinusoids at practically unaltered level of sinusoidal filtration. The above shifts were observed against the background of constriction of arterial, portal, venous and lymphatic vessels and of a decrease in capacitance of the liver vessels which were due to alpha-adrenocereptors excitation by noradrenaline.

Isoproterenol inhibits the increase in microvascular membrane permeability produced by bradykinin

Bradykinin (BRADY) is hypothesized to cause the "capillary leak" syndrome in patients with sepsis, trauma, and burns. Our purpose was to determine if isoproterenol (ISO) reversed a BRADY-produced accelerated loss of intravascular fluid and protein into the interstitium of skin. An increase in microvascular permeability in canine hind paw skin was sustained by a continuous femoral artery infusion of BRADY (0.2 micrograms/kg/min). After 2 hours of BRADY, skin lymph flow (LYM FLOW microliters/min) increased nine-fold and skin lymph-to-plasma total protein concentration ratio (RTP) was substantially increased. Mean blood flow in the femoral arteries was increased four-fold by the BRADY infusion. After 2 hours of BRADY-induced increased permeability, five of the ten dogs were started on intravenous ISO (2 micrograms/min continuously) which increased heart rate from 182 +/- 15 to 222 +/- 11 beats/min. ISO reversed the increase in RTP produced by the BRADY. After 8 hours of BRADY, there was less tissue albumin in the dogs given ISO (14.5 +/- 2.0 vs. 29.5 +/- 6.6 mg/gram dry wgt, p less than 0.05 unpaired t-test). ISO can reverse the sustained increase in skin microvascular permeability produced by BRADY.

Effects of ANP on venous pressures and microvascular protein permeability in dog forelimb

Intravenous administration of alpha-atrial natriuretic peptide (ANP) produces a decrease in arterial blood pressure due to a decrease in cardiac output. The mechanism of the decrease in cardiac output is unknown but has been suggested to result from transcapillary fluid efflux caused by venoconstriction and/or increased permeability of the microvascular membrane to plasma proteins. We investigated these possibilities in the dog forelimb perfused at constant flow and prepared to measure 1) large and small vessel pressures in the two parallel skin and skeletal muscle vascular beds, and limb weight; or 2) skin lymph flow and skin lymph protein concentration. In both preparations, human ANP was injected and infused into the brachial artery. Bolus injections of ANP (0.1-0.4 micrograms) depressed perfusion pressure much less than acetylcholine or an isotonic solution of potassium chloride and did not raise small vein pressures. ANP infused at nine different rates ranging from 0.1 ng to 38.8 micrograms/min failed to influence skin and muscle small and large vein pressures, limb weight, skin lymph flow, and skin lymph protein concentration. It also failed to affect perfusion pressure and skin and muscle small artery pressures until the infusion was shut off, at which time they increased above control levels. These studies suggest that human alpha-ANP is neither a direct venous constrictor nor a potent arteriolar dilator and does not directly influence the permeability of the microvascular membrane to plasma proteins in the skin and skeletal muscle of the dog forelimb.

Effect of histamine on tracheobronchial afferent and caudal mediastinal efferent lymph

We prepared nine sheep with acute tracheobronchial afferent (TBN) and caudal mediastinal efferent (CMN) lymph fistulas. After a baseline period (B) in 3 sheep, we administered histamine (H) continuously for 4 h. In six sheep, we elevated left atrial pressure (PLA) and reestablished steady-state conditions prior to H administration. The afferent lymph to plasma protein concentration ratio (CA/CP) was significantly lower than the efferent ratio (CE/CP) during periods of B, H, elevated PLA, and elevated PLA with H. H administration increased lymph flow rates (QlA and QlE) and both CA/CP and CE/CP, albeit insignificantly. During elevated PLA, QlA and QlE increased, while CA/CP and CE/CP fell. QlE increased, while QlA did not change during elevated PLA with H. CE/CP increased from its PLA level. CA/CP did not increase. Afferent data suggest that histamine may increase pulmonary microvascular surface area, but does not alter the permeability of the pulmonary circulation. While we cannot exclude the possibility of an increase in pulmonary microvascular permeability from efferent results, the difference between TBN afferent and CMN efferent results likely represent the action of histamine at the CMN.

[Pharmacologic agents that stimulate the drainage function of the lymphatic system]

Modern pharmacological agents used in experimental and practical medicine to stimulate the drainage function of the lymphatic system are discussed. Lymphotropic agents differ by the chemical structure and mechanism of action. Much attention is paid to the analysis of the agents possessing the osmotic effect. Particular emphasis is given to natural bioflavonoids including new polyphenol compounds produced from the Siberian plants.

The rapid induction by interleukin-2 of pulmonary microvascular permeability

The clinical use of interleukin-2 (IL-2) is limited by severe cardiopulmonary dysfunction. This study examines the mechanism of respiratory failure related to IL-2, using sheep with chronic lung lymph fistulae. Awake animals were infused with an intravenous (I.V.) bolus of IL-2 10(5) U/kg (n = 5) or its excipient (EXC) control (n = 3), every 8 hours for 4 to 5 days. Cardiopulmonary function was monitored daily for at least one 8-hour period. Within 2 hours after each IL-2 administration, mean pulmonary arterial pressure (MPAP) rose. On Day 1, the mean rise was from 13 to 26 mmHg (p less than 0.05), and on Day 5, to 29 mmHg (p less than 0.05). MPAP returned to baseline levels after 2-3 hours. Pulmonary arterial wedge pressure was unchanged from 4 mmHg. There were transient falls in arterial oxygen tension, from 88 to 77 mmHg on Day 1 and to 73 mmHg (p less than 0.05) on Day 5. Lung lymph flow (QL) rose from 2.4 to 6.8 ml/30 minutes (p less than 0.05) on Day 1, and from 4.7 to 10.2 ml/30 minutes (p less than 0.05) on Day 5, whereas the lymph/plasma protein ratio increased on Day 1 from 0.69 to 0.83 (p less than 0.05) and from 0.63 to 0.71 (p less than 0.05) on Day 5. This documents an increase in pulmonary microvascular permeability. Thromboxane (Tx)B2 levels increased transiently after each IL-2 injection in plasma from 195 to 340 pg/ml (p less than 0.05) and in lung lymph from 222 to 772 pg/ml (p less than 0.05) on Day 1, and to similar levels on Day 5. There was a progressive rise in cardiac output from 5.7 to 8.6 1/minute (p less than 0.05) during the 5 days of infusion. Systemic blood pressure did not change. Temperature rose from 39.1 to 41.2 C (p less than 0.05), and shaking chills were common. There was a progressive fall in leukocyte count, from 8.4 to 3.2 X 10(3)/mm3 (p less than 0.05) by Day 5, reflecting a 77% fall in lymphocytes. Lung lymph lymphocyte counts rose, and lymphocyte clearance increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of platelet-activating factor antagonist SRI 63-441 on endotoxemia in sheep

We investigated whether platelet-activating factor (PAF) mediates endotoxin-induced systemic and pulmonary vascular derangements by studying the effects of a selective PAF receptor antagonist, SRI 63-441, during endotoxemia in sheep. Endotoxin infusion (1.3 micrograms/kg over 0.5 h) caused a rapid, transient rise in pulmonary arterial pressure (Ppa) from 16 +/- 3 to 36 +/- 10 mmHg (P less than 0.001) and pulmonary vascular resistance (PVR) from 187 +/- 84 to 682 +/- 340 dyn.s.cm-5 (P less than 0.05) at 0.5 h, followed by a persistent elevation in Ppa to 22 +/- 3 mmHg and in PVR to 522 +/- 285 dyn.s.cm-5 at 5 h in anesthetized sheep. Arterial PO2 (PaO2) decreased from 341 +/- 79 to 198 +/- 97 (P less than 0.01) and 202 +/- 161 Torr at 0.5 and 5 h, respectively (inspired O2 fraction = 1.0). SRI 63-441, 20 mg.kg-1.h-1 infused for 5 h, blocked the early rise in Ppa and PVR and fall in PaO2, but had no effect on the late phase pulmonary hypertension or hypoxemia. Endotoxin caused a gradual decrease in mean aortic pressure, which was unaffected by SRI 63-441. Infusion of SRI 63-441 alone caused no hemodynamic alterations. In follow-up studies, endotoxin caused an increase in lung lymph flow (QL) from 3.8 +/- 1.1 to 14.1 +/- 8.0 (P less than 0.05) and 12.7 +/- 8.6 ml/h at 1 and 4 h, respectively. SRI 63-441 abolished the early and attenuated the late increase in QL.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of inhibition of 5-lipoxygenase metabolism of arachidonic acid on response to endotoxemia in sheep

We studied the effects of a 5-lipoxygenase inhibitor, L-651,192, on the pulmonary dysfunction caused by endotoxemia in chronically instrumented unanesthetized sheep. The efficacy and selectivity of L-651,392 were tested by measuring in vivo production of leukotriene B4 (LTB4) and cyclooxygenase products of arachidonic acid after endotoxemia before and after pretreatment with L-651,392 and ex vivo from granulocytes and whole blood stimulated with calcium ionophore from sheep before and 24 h after pretreatment with L-651,392. A novel assay for LTB4 by high-performance liquid chromatography/gas chromatography/mass spectrometry techniques was developed as a measure of 5-lipoxygenase metabolism of arachidonic acid. L-651,392 proved to be an effective in vivo 5-lipoxygenase inhibitor in sheep. L-651,392 blocked the increase in LTB4 observed in lung lymph after endotoxemia in vivo in sheep as well as inhibited by 80% the ex vivo production of LTB4 by granulocytes removed from sheep treated 24 h earlier with L-651,392. Although L-651,392 blocked the increase in cyclooxygenase products of arachidonic acid observed in lung lymph after endotoxemia in vivo in sheep, the drug probably did not function directly as a cyclooxygenase inhibitor. L-651,392 did not attenuate the ex vivo production of thromboxane B2 by whole blood from sheep treated 24 h earlier with the drug. L-651,392 attenuated the alterations in pulmonary hemodynamics, lung mechanics, oxygenation, and lung fluid and solute exchange observed after endotoxemia in sheep. We speculate that 5-lipoxygenase products are a major stimulus for cyclooxygenase metabolism of arachidonic acid after endotoxemia in sheep.

[The immunodepressive and lympholytic action of kortifen]

The study of the effect of a new antitumor drug cortifen on humoral immunity in experiments on CBA mice showed that it is a potent and long acting immunodepressant. The degree of immunity depression was found to be drug dose-dependent. The hormonal components of cortifen failed to exert the immunodepressive action. The alkylating component, chlorphenacyl, on the contrary, had the immunostimulating effect.

Corticosteroids inhibit endotoxin-induced lung lymph neutrophil stimulating activity in sheep

The Adult Respiratory Distress Syndrome (ARDS) most frequently is the result of sepsis. Accumulation of neutrophils in lung interstitium is a well-documented phenomenon, but the nature of their presence remains obscure. We hypothesized that endotoxin causes the release of substances into lung lymph that activate neutrophils and that methylprednisolone may prevent sequestration and activation of neutrophils. We used the sheep lung lymph fistula-endotoxin model of ARDS to test this hypothesis. Unanesthetized animals were given either 0.5 microgram/kg of E. coli endotoxin intravenously alone or, on a different experimental day, an identical dose of endotoxin preceded by a 1 gm bolus of methylprednisolone plus a 1 gm/hr continuous infusion. Endotoxin infusion caused the release of substances into lung lymph that were capable of stimulating normal sheep neutrophils to aggregate, migrate, and release superoxide. This activity appeared within 1 hour of endotoxin and persisted for at least 4 hours. Pretreatment by methylprednisolone did not prevent the early activity but did significantly reduce such activity 3-4 hours after endotoxin, when the permeability defects caused by endotoxin are most pronounced. We speculate that endotoxin-stimulated production of humoral neutrophil-activating substances in the lung may play a role in the pathogenesis of acute lung injury.

Contribution of kininase II to the waning of vascular actions of bradykinin

The mechanism(s) of the waning of the vasodilation and increase in vascular permeability during prolonged local intraarterial infusions of bradykinin (BK) was investigated in this study. Treatment with phentolamine or saralasin failed to prevent the waning of the vasodilation during the prolonged infusion of BK into forelimbs perfused at constant flow. In contrast, BK produced a sustained vasodilator response after treatment with captopril. Forelimb weight and lymph analysis were used to quantitate edema formation and to determine the duration of the increase in vascular permeability during prolonged local intra-arterial infusions of BK into forelimbs perfused at constant flow. The lymph-to-plasma ratios (L/P) for protein and FITC-Dextrans (fluorescein isothiocyanate dextrans, 70,000 Da) were determined, and clearances for protein and FITC-D were calculated. BK markedly increased fluid filtration, the protein L/P, and protein clearance resulting in edema formation. The protein L/P remained markedly elevated throughout the experimental period. The FITC-D L/P was markedly increased in the groups of animals in which the tracer was injected intravenously at the start or 8 min after the start of the prolonged BK infusion. In the groups of animals in which the tracer was injected intravenously 15-60 min after the start of the prolonged BK infusion, the FITC-D L/P failed to exceed the FITC-D L/P in control animals, although the protein L/P remained elevated. Pretreatment with both captopril and propranolol dramatically potentiated the magnitude of the increase in protein clearance, the filtration rate, and edema formation produced by BK but failed to affect the duration of the transient increase in vascular permeability.

The lymphogogue action of calcium dobesilate on the flow of lymph from the thoracic duct of anesthetized and mobile guinea pigs

Calcium dobesilate increases thoracic duct lymph flow in both anesthetized and mobile guinea pigs. The marked lymphogogue action of this drug may explain in part the improvement in tissue survival with ischemic insult.

Cardiopulmonary changes with intermittent endotoxin administration in sheep

Chronic sepsis was induced by administering endotoxin (lipopolysaccharide--LPS) at 12-hr intervals to sheep. The animals (n = 7) responded to the first dose of LPS with increased pulmonary arterial pressure (PAP), systemic vascular resistance, plasma and lymph thromboxane B2 (TxB2) concentrations, and lung lymph flow rate concurrent with a reduction in the cardiac index (CI). Subsequent doses of LPS produced an elevation of PAP and TxB2 which was progressively attenuated and eventually disappeared. With LPS the lung lymph flow was markedly elevated and CI increased. This latter was transient and associated with a reduction in systemic vascular resistance. Concomitant with the cardiopulmonary changes prekallikrein levels were not diminished, but there was a statistically significant reduction in C1-esterase inhibitor. The administration of LPS was discontinued after 5 days and the cardiopulmonary variables rapidly returned to baseline levels. Chronic endotoxemia appears to be associated with an elevated pulmonary microvascular permeability and a tendency toward a hyperdynamic circulation but with an appreciable degree of refractoriness associated with regional hemodynamics and eicosanoid biosynthesis.

Prostaglandin E2 attenuation of sheep lung responses to endotoxin

Prostaglandin (PG) E2 can inhibit inflammatory responses of neutrophils and lymphocytes, including eicosanoid release. Diffuse lung injury after endotoxemia in sheep is accompanied by sequestration of neutrophils and lymphocytes in the lungs, and eicosanoids mediate some of the pathophysiology of the response. To determine whether exogenous PGE2 could prevent the endotoxin response, we measured pulmonary hemodynamics, gas exchange, and lung lymph responses to infusion of Escherichia coli endotoxin (0.5 micrograms/kg iv over 30 min) in unanesthetized sheep in the presence and absence of PGE2 (0.5 micrograms.kg-1.min-1) infused intravenously for 4 h beginning 0.5 h before endotoxin infusion. We also measured lung lymph concentrations of thromboxane B2 (TxB2) and prostacyclin metabolite, 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), by radioimmunoassay and leukotriene B4 (LTB4) by gas chromatography-mass spectrometry. PGE2 decreased endotoxin-induced pulmonary hypertension and hypoxemia and markedly attenuated the lymph flow and lymph protein clearance responses. PGE2 also attenuated endotoxin-induced increases in lung lymph TxB2 and 6-keto-PGF1 alpha and decreased lymph LTB4 flow after endotoxin without decreasing lymph LTB4 concentrations. We conclude that PGE2 infusion attenuates lung dysfunction caused by endotoxemia, possibly by preventing endogenous release of other eicosanoids.

Effects of beta-adrenergic agents in lungs of normal and air-embolized awake sheep

It is unclear whether beta-adrenergic agonists or antagonists affect lung liquid and protein exchange by changing pulmonary hemodynamics or microvascular leakiness. In 23 unanesthetized, instrumented sheep with long-term lung lymph fistulas, we assessed the effect of the beta-agonist terbutaline or the beta-antagonists propranolol, nadolol, and atenolol, all infused intravenously, on lung lymph flow under base-line conditions and during the acute lung injury caused by 4 h of venous air embolism. Under base-line conditions, neither beta-stimulation nor blockade had any effect. During air embolism, terbutaline decreased pulmonary vascular resistance and lymph flow by 25%. Propranolol and nadolol (non-selective beta 1,beta 2-antagonists) but not atenolol (selective beta 1-antagonist) also decreased lymph flow by 22% on average. We favor the more conservative (hemodynamic) over the more liberal (altered permeability) explanation for our results. First, beta-stimulation clearly caused vasodilation, which lowered the pulmonary microvascular pressure at the site of injury. beta-blockade caused changes similar to alpha-stimulation (J. Appl. Physiol. 62: 2147-2153, 1987). We therefore interpret the beta-blockade as unmasking pulmonary arterial alpha-receptors stimulated by the air-embolism injury, thus allowing vasoconstriction upstream to the site of injury. We do not believe the explanation of the beta-agent effects requires any modulation of lung microvascular leakiness by beta-adrenergic agents.

Aminophylline attenuates the edemogenic actions of histamine in the canine forelimb

Xanthines have been employed clinically to treat asthma and related pulmonary conditions because of their bronchodilator properties. In addition, xanthines have been reported to block and/or attenuate the increase in microvascular permeability to macromolecules produced by some putative inflammatory mediators. In order to more completely assess the anti-inflammatory capabilities of xanthines, we have infused aminophylline intra-arterially in the canine forelimb prior to and during a local intra-arterial infusion of histamine. Forelimb prenodal lymph flow, protein concentration and protein transport were used as indices of transvascular fluid and protein flux. Infusion of histamine (4 micrograms/min) significantly decreased forelimb arterial pressures and increased lymph flow, protein concentration and protein transport. Aminophylline infusion (10 mg/min) decreased forelimb arterial pressures but did not affect lymph parameters. Histamine infusion during infusion of aminophylline increased lymph parameters but the increases were markedly less than with histamine infusion alone. Infusion of aminophylline (20 mg/min) decreased forelimb arterial pressures and systemic pressure. Subsequent histamine infusion resulted in small but significant increases in lymph parameters. These data indicate that aminophylline infusion can blunt the ability of subsequently administered histamine to increase microvascular permeability as evidenced by the attenuation of the increases in lymph flow, protein concentration and protein transport.

Fetal thoracic duct lymph flow response to intravascular saline infusion

The left thoracic lymph duct was catheterized at the base of the neck in the sheep fetus at 123-136 days of gestation, and the lymphatic catheter was connected to a jugular vein catheter so that the lymph could return to the fetus. Lymph flow was studied 5 days after catheter implantation in the unanesthetized fetus. Basal fetal thoracic duct lymph flow rate per unit body weight averaged three times adult sheep values. After an infusion of 20 ml/kg of warmed isotonic saline into a fetal vein over 5 min, lymph flow rate increased significantly to 161 +/- 15% of control, with a peak at 8 min after termination of the infusion, and flow declined thereafter. The increased lymph volume above baseline values over 30 min averaged 5.7% of the infused volume and is similar to the adult response. Plasma and lymph protein concentrations decreased as did the lymph-to-plasma protein concentration ratio. The latter is opposite to what occurs in the adult under the same conditions. Thus the present study shows that even though the fetus has a much higher basal thoracic duct lymph flow rate than the adult, the responsiveness of the fetal lymphatic system to intravascularly infused saline is similar to that of the adult. The decrease in the lymph-to-plasma protein concentration ratio suggests that there may be differences between fetal and adult vascular-interstitial-lymphatic protein kinetics.