Lymph Protein Concentration Research Articles

The possible role of acetate in exercise hyperemia in dog skeletal muscle.

The possible role of acetate in the genesis of exercise hyperemia was studied in five series of dogs. Intraarterial infusion of an isomotic solution of sodium acetate at 0.76 ml/min in the dog forelimb decreased the resistance to flow through skeletal muscle by 48%, primarily by decreasing resistance to flow through small vessels. Skin lymph flow and lymph protein concentration were unaffected. The hindlimb of the conscious dog took up acetate at rest (A-V difference, + 58.3 +/- 19.6 nmoles/ml) and put out acetate during treadmill exercise (A-V difference, -105.6 +/- 20.12 nmoles/ml); femoral venous blood acetate concentration increased by 145 nmoles/ml (control 195 nmoles/ml). In the gracilis muscle of the anesthetized dog, simulated exercise at 0.5, 1.0 or 2.0 Hz increased acetate tissue content (72, 248 and 442 nmoles/g, respectively), output (18,899, and 1,830 nmoles/100 g/min, respectively) and venous concentration (82, 49 and 39 nmoles/ml, respectively) and changes in tissue acetate content correlated with changes in vascular resistance r = 0.75, P less than 0.001. Intraarterial infusion of an isosmotic solution of sodium acetate in the quiescent gracilis muscle perfused at constant flow produced a significant (6%) decrease in resistance when arterial blood acetate was increased by a calculated 96 nmoles/ml. These studies suggest that acetate might be included among those metabolites that contribute to exercise hyperemia.U

Prostaglandin release and altered microvascular integrity after burn injury

Alterations in microvascular integrity occur after thermal injury in both burned and nonburned tissues including the lung resulting in increases in transvascular fluid and protein flux. Our purpose was to determine the role of the potent vasoactive prostaglandins, prostacyclin (PGI 2) and thromboxane (TxA 2), in this process. We monitored fluid flux and protein permeability in lung, and in burned (B) and nonburned (NB) soft tissue using lymph flow, Q ̇ L , and lymph protein content in 14 adult sheep after a 30% body burn. We measured levels of TxA 2 as TxB 2 and PGI 2 as 6-keto-PGF 1α in lymph and plasma over a 48-hr period. Q ̇ L increased by 200–300% in lung and NB tissue in the first 12 hr, returning to baseline by 48 hr. Protein permeability was unchanged in lung and transiently increased in NB. Lymph PGI 2 was increased, from 0.3 to 1.5 ng/ml in lung and 0.5 to 1.7 ng/ml in NB. Levels returned to baseline with Q ̇ L . TxB 2 levels were not increased. In B tissue, Q ̇ L increased by 5- to 10-fold as did protein permeability, with PGI 2 levels increasing from 0.3 to 10.9 ng/ml. Both Q ̇ L and PGI 2 remained increased for over 48 hr. TxB 2 was unchanged. We, therefore, found that variable degrees of microvascular change occurred in lung, NB, and B soft tissue after thermal injury. Lymph PGI 2 corresponded in both degree and time course with the measured microvascular injury. Thromboxane did not appear to play a role in this process.

Effect of hypercapnia on net filtration of fluid in the lungs of awake newborn lambs.

To study the effect of hypercapnia on net transvascular filtration of fluid in newborn lungs, we measured pulmonary arterial and left pressures and collected lung lymph from 11 awake 2-wk-old lambs as they spontaneously breathed a gas mixture rich in carbon dioxide. After a 2-h control period in air, the lambs breathed 8-11% carbon dioxide mixed with air and nitrogen for 2-6 h. Average pulmonary arterial pressure and blood flow to the lungs increased during hypercapnia, but pulmonary vascular resistance did not change. In all cases, hypercapnia led to an acute transient increase in lymph flow. During sustained hypercapnia, however, flow of lymph was not significantly different from flow measured during the control period. The concentration of protein in lymph decreased at the onset of hypercapnia and remained low during sustained hypercapnia. These results suggest that acute hypercapnia increases net filtration by increasing the transvascular gradient of hydraulic pressure, whereas, in a "steady-state," neither hypercapnia nor the tachypnea that accompanies it alters net transvascular filtration of fluid in the lungs of unanesthetized newborn animals.

Increased pulmonary vascular permeability following acid aspiration.

The effect of hydrochloric acid aspiration on transvascular fluid and protein flux and lung water content was studied in 21 anesthetized dogs. We measured steady-state lung lymph flow, pulmonary arterial and left atrial pressures, and the concentration of total protein and albumin in both lymph and plasma after intratracheal instillation of 2 ml/kg 0.1 N HCl. Acid injury produced a twofold increase in lung lymph flow and lymph protein clearance when compared with control. This indicated an increase in pulmonary microvascular permeability. In dogs given 25 g concentrated human albumin and 1 mg/kg furosemide 10 min after the acid injury, the acid-induced increase in fluid filtration was prevented. However, the decrease in fluid filtration was not attributed to an increase in the transvascular protein osmotic pressure gradient but to a more direct effect of furosemide. Treatment with furosemide alone prevented the increase in lung lymph flow induced by acid injury, whereas albumin alone did not. In all acid-injured animals there was an increase in lung water when compared wtih control. Therefore acid aspiration produced localized areas of damage to filtration vessels that lead to increased leakage of protein and water. Furosemide treatment prevented much of this increased fluid and protein flux by an undefined mechanism.

Effect of secretin on intestinal lymph flow and composition in the rat.

The effects of natural porcine and synthetic secretin, given by intravenous bolus or infusion, on intestinal lymph flow and protein composition in unanaesthetized rats were studied. Both forms of secretin increased lymph flow and protein output from the lymph fistula; dose-response relationships were determined. No change was observed in protein concentration in lymph or in the relative concentrations of large and small protein molecules during secretin-induced enhanced lymph flow, compared with the basal state. These results are in keeping with an increase in the functional exchange vessel area of the small intestine produced by secretin. It is possible that secretin may play a part in the hyperaemia and augmented intestinal lymph flow which occurs in the post-prandial period.

Interstitium-to-blood movement of macromolecules in the absorbing small intestine.

The relative roles of diffusion and convection in the transport of plasma proteins across intestinal capillaries were estimated for absorbing and nonabsorbing segments of cat ileum. Diffusive, convective, and net protein fluxes were estimated with steady-state lymph and plasma protein concentrations, lymph flow, net transmucosal volume flow, and phenomenological transport equations. The results acquired indicate that convection accounts for approximately 80-90% of total net transcapillary solute movement at normal and increased capillary filtration rates. When the intestinal capillaries are converted from filtering to absorbing vessels by enhancing transmucosal water movement, the convective and diffusive protein fluxes occur in opposite directions, i.e., significant quantities of plasma proteins move from interstitium to blood by convection. These findings suggest that the magnitude of the capillary protein leakage during absorption is far greater than predicted using lymphatic protein flux changes. The massive movement of plasma proteins into and out of the mucosal interstitium during absorption may be advantageous for the removal of protein-bound nutrients (e.g., fatty acids).

Lung fluid and protein exchange in the acute sheep preparation

We examined the effect of left atrial hypertension on lung fluid and protein exchange in acutely prepared anesthetized sheep. The results were compared with those reported by Erdmann jet al. (Circ. Res. 37:271-284, 1975) in chronically instrumented conscious sheep. Animals were anesthetized with halothane and efferent duct of the caudal mediastinal node was cannulated. Pulmonary microvascular pressure (Pmv) was elevated by raising left atrial pressure with a left atrial balloon. For every elevation in Pmv of 1 cmH2O pulmonary lymph flow (Qlym) increased by 0.5 ml/h. Increasing the Pmv resulted in a linear decrease (p less than 0.05) in the ratio of lymph to plasma protein concentration as a result of a significant reduction in lymph protein concentration. Transvascular clearance of lymph proteins increased by 39% with a doubling of Qlym. The steady-state changes in pulmonary fluid and protein exchange induced by an increase in Pmv in acutely prepared anesthetized sheep were the same as those observed by Erdmann et al. in chronically instrumented unanesthetized sheep, indicating that the acute preparation is equally reactive to increase in Pmv and that the lung endothelial permeability is not increased.

Blockade of histamine-mediated increases in microvascular permeability by H 1- and H 2-receptor antagonists

The receptor mechanisms by which histamine increases microvascular fluid and protein efflux were studied in the canine forelimb perfused at constant flow. Skin lymph flow, protein concentration, and protein transport (flow × concentration) were examined during the intraarterial infusion of histamine alone and during the simultaneous infusion of histamine and the histamine antagonists tripelennamine or cimetidine. The infusion of histamine alone at 1.4 μg base/min resulted in a significant decrease in forelimb perfusion pressure and skin small-artery pressure and a small but significant increase in skin small-vein pressure. Histamine produced a 2 1 2 - fold increase in lymph flow, a 2-fold increase in lymph protein concentration, and a 5-fold increase in lymph protein transport. Infusion of this same dose of histamine during the simultaneous infusion of the H 1-receptor antagonist tripelennamine (10 μg/min) produced essentially the same changes in forelimb vascular pressures but failed to produce significant changes in lymph flow, lymph protein concentration, or lymph protein transport. Similarly, the infusion of cimetidine (250 μg/min), an H 2-receptor antagonist, concurrent with the infusion of histamine elicited no significant changes in lymph parameters but the fall in arterial pressures was attenuated. Since either an H 1- or an H 2-receptor antagonist is capable of blocking histamine-mediated increases in lymph flow and protein concentration, these data indicate a role for both H 1 and H 2 receptors in histamine-mediated increases in microvascular permeability.

Effects of histamine and histamine antagonists on intestinal capillary permeability.

Steady-state lymph flow, blood flow, and lymph and plasma total protein concentration were measured in an autoperfused cat ileum preparation during the continuous infusion of histamine at venous pressures of 0, 10, 20, and 30 mmHg. The capillary osmotic reflection coefficients for total proteins and each protein fraction were estimated. In addition, the ileum was pretreated with an H1-receptor antagonist (diphenhydramine) or with an H2-receptor antagonist (cimetidine). The results suggest that histamine selectively increases the ileal vascular permeability to plasma proteins of a molecular radius up to 96 A. The H1-receptor antagonist did not alter the histamine-induced permeability changes but did block the observed initial vasodilation. The H2-receptor antagonist significantly reduced the permeability changes associated with histamine while having only a slight effect on the initial vasodilation. It is concluded that the activation of H1-receptors is predominantly associated with the initial vasodilation, whereas the H2-receptors are predominantly associated with permeability.

148 LUNG FLUID IN HYPOXIC LAMBS

In newborn lambs, alveolar hypoxia for 3-6 h increases filtration pressure in the pulmonary microcirculation and drives fluid into the lungs: pulmonary lymph flow increases and the concentration of protein in lymph decreases (Circ Res 46:111, 1980). To be certain that the increased lymph flow was not simply the result of an acute release of fluid from the lungs, we assessed lung fluid balance in 4 unanesthetized lambs kept hypoxic for 12 h. We used radioactive albumin tracers to see if sustained hypoxia altered microvascular permeability to protein in the lungs. After a 2-4 h control period in air, the lambs breathed 10% O2 and 5% CO2. We measured pressures in the pulmonary artery (Ppa) and left atrium (Pla); lung blood flow (Qb) and lymph flow (Q1); and concentrations of protein in lymph (Lp) and plasma (Pp). During control and experimental periods, we injected 125I-albumin intravenously and determined the time at which specific activity in lymph reached 1/2 that in plasma (T½). Results (X ± sx; *p <.05): In all lambs, Ppa, Qb, and Q1 remained up for the duration of hypoxia; pulmonary vascular resistance increased 62 ± 4%; Lp was persistently low; and T½ did not change. We conclude that prolonged alveolar hypoxia causes a sustained increase in transvascular filtration of fluid into the lungs of lambs; hypoxia does not influence microvascular permeability to protein in the lungs.

1319 VITAMIN E DOES NOT PREVENT OXYGEN-INDUCED LUNG INJURY IN LAMBS

Lung microvascular permeability to protein increases in lambs that breathe 100% O2 for 3-5 days. We tried to prevent this injury by giving vitamin E to 6 lambs. After 4 h in air, the lambs breathed 100% O2 continuously. They received vitamin E, 20 mg/kg/d IM for 2 days before and throughout the study. To assess lung fluid filtration and microvascular permeability to protein, we measured pulmonary arterial (PA) and left atrial (LA) pressures, lung lymph flow, and concentrations of protein in lymph and plasma. Before and 3 days after starting O2, we gave 125I-albumin IV to 4 lambs and determined the time at which specific activity in lymph reached 1/2 that in plasma (T½). Results (X ± sx): *=per g dry lung underline=significant difference, p< .05 Despite a 10-fold increase in plasma tocopherol levels, lymph flow tripled, the concentration of protein in lymph increased, and T½ decreased. These results show that pulmonary microvascular permeability to protein increased during O2 breathing. All lambs died of respiratory failure within 4 days. Postmortem lung water was 25% greater than that of normal lambs, and lung histology showed extensive pulmonary edema. We conclude that vitamin E was ineffective in preventing or lessening lung injury from O2.

Intravenous infusion of tolazoline reduces pulmonary vascular resistance and net fluid filtration in the lungs of awake, hypoxic newborn lambs.

In newborn lambs, alveolar hypoxia increases pulmonary microvascular pressure, causing an increase in lung lymph flow and a decrease in the concentration of protein in lymph. To see if reducing pulmonary vascular resistance during hypoxia might decrease net transvascular filtration of fluid in the newborn lung, we measured vascular pressures and cardiac output, and collected lung lymph from 10 unanesthetized lambs 1 to 3 wk of age before and during hypoxia, and then during a constant intravenous infusion of tolazoline, an α-adrenergic blocker. After a 2-h control period in air, the lambs breathed10 to 12% oxygen in nitrogen for 2 to 3 h; then, during sustained hypoxia, we gave tolazoline (2 mg/kg of body weight) by rapid intravenous injection, followed by a constant infusion at a rate of 4 mg/kg/h for 2 to 3 h. During hypoxia alone, pulmonary vascular resitance increased 69%, lymph flow increased 84%, and lymph protein concentration decreased. During persistent hypoxia and infusion of tolazoline, pulmonar...

Elevated sialyltransferase activity in the intestinal lymph of colchicine-treated rats

There is a marked increase of sialyltransferase activity (EC 2.4.99.1) in serum and a profound change in the endogenous acceptor property of sialyl-transferase in the intestine of colchicine treated rats (Fraser, Ratnam, Collins and Mookerjea, (1980) J. Biol. Chem. 255, 6617–6625). To ascertain the contribution of intestine as a source of this elevated serum enzyme, sialyltransferase and other enzyme activities were measured in intestinal lymph before and after colchicine treatment. There was a 4-fold increase of the enzyme activity in lymph 3 h after treatment. The lymph flow rate, protein concentration and composition as measured by polyacrylamide gel electrophoresis were not affected. The kinetic properties of lymph sialyltransferase (protein and time dependence, pH optima and K m values for the substrate CMP-sialic acid) were essentially unchanged after treatment and were similar to the serum sialyltransferase. Alkaline phosphatase and lactic dehydrogenase activities were elevated in the lymph whereas maltase and lactase activities remained unchanged. Although intestinal lymph sialytransferase was increased by colchicine, enterectomy did not prevent the rise of serum sialyltransferase suggesting that the intestine is not a major source of the serum enzyme.

Permeability characteristics of colonic capillaries.

Blood flow, lymph flow, lymph protein concentration (CL), lymph oncotic pressure, plasma protein concentration (CP), and plasma oncotic pressure were determined under steady-state conditions at venous pressures of 0, 10, 20, 30, and 40 mmHg in autoperfused segments of dog colon. Venous pressure elevation increased colonic vascular resistance, lymph flow, lymphatic protein flux, and the transcapillary oncotic pressure gradient, whereas the lymph-to-plasma protein concentration ratio (CL/CP) declined. The osmotic reflection coefficient (sigma d) was estimated using sigma d = 1-CL/CP when CL/CP is filtration independent (high lymph flows). For total protein sigma d = 0.85 +/- 0.02. Values of sigma d for plasma protein fractions with molecular radii ranging between 37 and 120 A increased as molecular radius increased. The results of this study suggest that 1) colonic capillaries selectively restrict macromolecules on the basis of molecular size, and 2) an increased lymph flow and transcapillary oncotic pressure gradient may play an important role in preventing interstitial edema subsequent to venous pressure elevation in the dog colon.

Effect of histamine and alloxan on canine pulmonary vascular permeability.

We estimated the pulmonary capillary membrane filtration coefficient (Kf) and the maximum capillary pressure (PCcritical) at which the lung could maintain a constant weight in 1) 5 control experiments in anesthetized open-chested dogs, 2) 7 experiments in which the dogs were given 3.6-8.3 microgram . kg-1 . min-1 of histamine phosphate, and 3) in 6 experiments after 75-100 mg/kg of alloxan. In additional experiments, pulmonary lymph flow (QL) and protein concentration (CL) were measured during the infusion of histamine and alloxan. After histamine, Kf averaged 0.045 +/- 0,008 ml . min-1mmHg-1 (SE) and PCcritical was 22.1 +/- 1.1 mmHg. These values were not significantly different from the control Kf and PCcritical (0.036 +/- 0.006 and 22.5 +/- 2.3, respectively). After alloxan, Kf (1.43 +/- 0.69) was larger and PCcritical (12.4 +/- 1.3) was significantly less than control (P less than 0.05). Histamine caused no significant change in QL or CL; however, both were increased after alloxan. These results show that Kf, PCcritical, QL, and CL are all changed by an increase in capillary membrane permeability caused by alloxan. Because none of these factors as significantly affected by histamine, dog lung capillary membrane permeability may not be affected by histamine.

Effect of albumin infusion on pulmonary microvascular fluid and protein transport

The effect of human albumin infusion on the dynamics of fluid and protein transport across the pulmonary microcirculation was studied. Lung lymph flow ( Q ̇ L ) from a chronic lung lymph fistula in unanesthetized sheep was used as a reliable indicator of transvascular fluid filtration rate ( Q ̇ L ). Lymph protein content was considered equal to interstitial protein content. Pulmonary vascular pressures, Q ̇ L , lymph and plasma proteins were continuously monitored. After a 4-hr baseline period, 50g of human, salt-poor albumin (400 cc) was infused over 0.5-hr. A hypersensitivity reaction occurred, in four studies, reflected in a large increase in pulmonary artery pressure and Q ̇ L . Mean data for the remaining six studies are summarized for baseline, after albumin infusion and 2 and 4 hr postinfusion. Microvascular pressure ( P mr, mm Hg) for the four periods was 8, 12, 8, and 8, while plasma colloid osmotic pressure ( π mv, mm Hg) was 21, 27, 24, and 24, respectively. Interstitial colloid osmotic pressure ( π mv) was 11, 11, 13, and 14 mm Hg. Q ̇ L was unchanged over the entire study period. We found that albumin infusion produced an immediate increase in plasma oncotic pressure and a transient increase in P mv. However, the colloid osmotic gradient between the interstitium and plasma returned to baseline by 4 hr despite a continued increase in plasma proteins as interstitial protein content increased in an equal manner. These data suggest a very transient, if any, decrease in lung extravascular fluid after albumin infusion.

The effects of isoprenaline and bradykinin on capillary filtration in the cat small intestine.

1 Lymph flow, and both lymph and plasma protein concentrations were measured in isolated, blood-perfused loops of cat ileum. 2 Permeability-surface ares (PS) products and the osmotic reflection coefficient (sigma) of the intestinal capillaries were calculated. 3 Isoprenaline (one dose) or bradykinin (two different doses) was infused into the superior mesenteric artery. 4 Isoprenaline (blood concentration about 50 ng/ml) did not affect PS or sigma. 5 Bradykinin (about 36 ng/ml) increased PS but as a sigma was unaltered, this was primarily due to an increased capillary surface area. 6 Bradykinin (about 680 ng/ml) increased PS and as sigma was reduced, there was an increased capillary permeability. 7 Reasons for the lack of effect of isoprenaline at concentrations which increase capillary filtration coefficient are discussed. 8 These data show that this technique separates drug effects on capillary surface area from effects on capillary permeability.

Lung fluid balance in awake newborn lambs with pulmonary edema from rapid intravenous infusion of isotonic saline.

To study pulmonary transvascular filtration of fluid and the normal adaptive response of newborn animals to excessive water in the lungs, we measured lung lymph flow, pulmonary vascular pressures, and the concentration of protein in lymph and plasma of nine unanesthetized 1- to 3-wk-old lambs, before, during, and after a rapid iv infusion of isotonic saline, 130-250 ml/kg.hr for 3-4 hr. During infusions, lung vascular pressures increased, the transvascular gradient of protein osmotic pressure decreased, and there was a 2- to 5-fold increase of lung lymph flow. When infusions stopped, lymph flow decreased, as the concentration of protein in plasma increased and pulmonary vascular pressures decreased to new steady-state levels. The concentration of protein in lymph did not change for several hours after the infusions. Body weight increased by 28% and extravascular lung water content was 19% above normal after saline; these changes were associated with mild tachypnea, hypercarbia, and hypoxemia. Sections of lung from these lambs had prominent cuffs of fluid surrounding large blood vessels.

Transsinusoidal fluid dynamics in canine liver during venous hypertension.

SUMMARY We studied arterial pressure, portal pressure, inferior vena caval pressure, hepatic interstitial pressure (implanted capsule technique), prenodal lymph flow, and the protein concentration in plasma and lymph in the anesthetized dog under normal conditions and during graded venous hypertension resulting from inferior vena caval occlusion. Under control conditions, portal, interstitial, and inferior vena caval pressures were 7.0, 5.8, and 2.0 mm Hg, respectively, and the lymph-plasma protein concentration ratio was 0.95. During acute venous hypertension, 64% of the inferior vena caval pressure increase was transmitted to the hepatic interstitium, and lymph flow increased 63% for every 1 mm Hg increment in interstitial pressure. The lymph-plasma protein concentration ratio did not change significantly during venous hypertension, indicating that: (1) the reflection coefficient of the sinusoidal wall for the major plasma proteins is close to zero, and (2) protein transport across the microvascular wall is due mainly to bulk flow. Using portal, interstitial, and inferior vena caval pressures as limits for possible values of sinusoidal pressure, our data suggest that (1) control sinusoidal pressure was between 5.8 and 7.0 mm Hg, and (2) approximately 90% of the increase in inferior vena caval pressure was transmitted to the sinusoids. The results indicate that changes in interstitial pressure, lymph flow, and surface transudation rate are major compensatory mechanisms operating in the liver to limit interstitial engorgement during venous hypertension. CireRea 45:317-323, 1979 THE LIVER, with its extensive vasculature and leaky sinusoids, plays a central role in the control of blood volume and cardiovascular fluid dynamics. More specifically, the high compliance of the hepatic vessels allows the liver to serve as a blood reservoir for maintenance of adequate cardiovascular filling during hemorrhage (Lautt and Greenway, 1976). In addition, in certain clinical conditions such as congestive heart failure, the free communication of the liver interstitium with the potential space of the peritoneal cavity provides a convenient route for spillage of excess plasma out of the circulation via the hepatic sinusoids (Greenway and Lautt, 1970). In general, transsinusoidal fluid flux should be governed by the same hydrostatic and oncotic forces that determine fluid movement across the capillary wall of other tissues (Starling, 1896). Unfortunately, the magnitude of each sinusoidal and

Increased sheep lung vascular permeability caused by Escherichia coli endotoxin.

We infused Escherichia coli endotoxin, 0.07-1.33 microgram/kg, intravenously into chronically instrumented unanesthetized sheep and measured pulmonary arterial and left atrial pressures, lung lymph flow, lymph and blood plasma protein concentrations, and arterial blood gases. Endotoxin caused a biphasic reaction: an early phase of pulmonary hypertension and a long late phase of steady state increased pulmonary vascular permeability during which pulmonary arterial and left atrial pressures were not increased significantly and lung lymph flow was 5 times the baseline value. Lymph: plasma total protein concentration ratio during the late phase (0.76 +/- 0.04) was significantly (P less than 0.05) higher than during baseline (0.66 +/- 0.03). The lymph response was reproducible. Lung lymph clearance of endogenous proteins with molecular radii (r) 35.5 to 96 A was increased during the steady state late phase of the reaction, but, as during baseline, clearance decreased as r increased. The endotoxin reaction was similar to the reaction to infusing whole Pseudomonas bacteria, except that endotoxin had less effect on pressures during the steady state response and caused a relatively larger increase in lymph clearance of large proteins. We conclude that E. coli endotoxin in sheep causes a long period of increased lung vascular permeability and may have a greater effect on large solute pathways across microvessels than do Pseudomonas bacteria.