Plasma protein osmotic pressure equations and nomogram for sheep

The equations developed by Landis and Pappenheimer (Handbook of Physiology. Circulation, 1963, p. 961-1034) for calculating the protein osmotic pressure of human plasma proteins have been frequently used for other animal species without regard to the fractional albumin concentration or correction for protein-protein interaction. Using an electronic osmometer, we remeasured the protein osmotic pressure of purified sheep albumin and sheep plasma partially depleted of albumin. We measured protein osmotic pressures of serial dilutions over the concentration range 0-180 g/l for albumin and 0-100 g/l for the albumin-depleted proteins at room temperature (26 degrees C). Using a nonlinear least squares parameter-fitting computer program, we obtained the equation of best fit for purified albumin, and then we used that equation together with the measured albumin fraction to obtain the best-fit equation for the nonalbumin proteins. The equation for albumin is IIcmH2O,39 degrees C = 0.382C + 0.0028C2 + 0.000013C3, where C is albumin concentration in g/l. The equation for the nonalbumin fraction is IIcmH2O,39 degrees C = 0.119C + 0.0016C2. Up to 200- and 100-g/l protein concentration, respectively, these equations give the least standard error of the estimate for each of the virial coefficients. The computed number-average molecular weight for the nonalbumin proteins is 222,000. Using the new equations, we constructed a nomogram, based on the one of Nitta and co-workers (Tohoku J. Exp. Med. 135: 43-49, 1981). We tested the nomogram using 144 random samples of sheep plasma and lymph from 31 sheep. We obtained a correlation coefficient of 0.99 between the measured and nomogram estimates of protein osmotic pressure.

Effect of thoracic duct drainage on hydrostatic pulmonary edema and pleural effusion in sheep

Positive end-expiratory pressure (PEEP) increases central venous pressure, which in turn impedes return of systemic and pulmonary lymph, thereby favoring formation of pulmonary edema with increased microvascular pressure. In these experiments we examined the effect of thoracic duct drainage on pulmonary edema and hydrothorax associated with PEEP and increased left atrial pressure in unanesthetized sheep. The sheep were connected via a tracheostomy to a ventilator that supplied 20 Torr PEEP. By inflation of a previously inserted intracardiac balloon, left atrial pressure was increased to 35 mmHg for 3 h. Pulmonary arterial, systemic arterial, and central venous pressure as well as thoracic duct lymph flow rate were continuously monitored, and the findings were compared with those in sheep without thoracic duct cannulation (controls). At the end of the experiment we determined the severity of pulmonary edema and the volume of pleural effusion. With PEEP and left atrial balloon insufflation, central venous and pulmonary arterial pressure were increased approximately threefold (P less than 0.05). In sheep with a thoracic duct fistula, pulmonary edema was less (extra-vascular fluid-to-blood-free dry weight ratio 4.8 +/- 1.0 vs. 6.1 +/- 1.0; P less than 0.05), and the volume of pleural effusion was reduced (2.0 +/- 2.9 vs. 11.3 +/- 9.6 ml; P less than 0.05). Our data signify that, in the presence of increased pulmonary microvascular pressure and PEEP, thoracic duct drainage reduces pulmonary edema and hydrothorax.

[The effect of pharmacological agents on the rate of lymph outflow and on blood and lymph toxicity in acute myocardial infarct]

In experiments on rabbits it was found that acute myocardial infarction (AMI) was associated with a disorder of the drainage function the lymphatic system and a drastic increase of the lymph toxicity. The administration of propranolol (obsidan), amiodaron (cordaron), lidocaine (xycaine), trimecaine (mesocaine), nitroglycerin, panangin and heparin exerted the pronounced stimulating action on the lymph outflow rate. Strophanthin-K, corglycon and digo in possessed the moderate lymphogenic effect. Novocainamide (procainamide), verapamil (isoptine) and panangin exerted no influence on the lymph outflow rate. The administration of the above mentioned drugs in the initial period of AMI sharply increased the toxic properties of the lymph; subsequently the lymph toxicity gradually decreased and was less than in control (in AMI treated with drugs).

Acetylcholine-induced release of endothelium-derived relaxing factor from lymphatic endothelial cells

Ring segments of dog thoracic ducts precontracted with a high concentration of norepinephrine (NE) relaxed in a concentration-dependent manner in response to acetylcholine (ACh) or sodium nitroprusside (SNP). Pretreatment with atropine inhibited the ACh-induced relaxation in a competitive manner. The Schild plot showed a slope of 1.1 +/- 0.2 and a pA2 value of 10.4 +/- 0.4 (n = 6 ring segments). Removal of endothelium caused a complete inhibition of the ACh-induced relaxations in precontracted dog thoracic ducts. ACh, which failed to relax precontraction of the ring segment when mounted separately, induced relaxation in the same preparation when it was mounted as a "sandwich" with the longitudinal strip. The ACh-induced relaxations in the lymphatic preparations with endothelium were suppressed or abolished by pretreatment with oxyhemoglobin (10(-6) and 10(-5) M), methylene blue (10(-6) and 10(-5) M), and NG-monomethyl-L-arginine (3 x 10(-5) M), but the relaxations were unaffected by aspirin (10(-5) M). Pretreatment with methylene blue (10(-5) M) also caused a significant reduction of the SNP-induced relaxations in the precontracted thoracic ducts. It may be concluded that ACh-induced relaxation in dog thoracic ducts precontracted with NE is mediated by high-affinity muscarinic receptors in the lymphatic endothelial cells. Also, stimulation of the endothelial muscarinic receptors liberates a transferable endothelium-derived relaxing factor, which results in the relaxation of the lymphatic smooth muscles via the accumulation of cellular guanosine 3',5'-cyclic monophosphate.

Effects of vasoconstrictive and vasodilative agents on lymphatic smooth muscles in isolated canine thoracic ducts

A study was made of the isometric responses of isolated canine thoracic ducts to several physiological vasoactive substances. Contractions of the lymphatic smooth muscles were induced by epinephrine, norepinephrine, 5-hydroxytryptamine, histamine (HIS) and prostaglandin F2 alpha in a dose-dependent manner. The decreasing order of potency in the contractile responses was as follows: epinephrine greater than norepinephrine greater than 5-hydroxytryptamine much greater than HIS not equal to prostaglandin F2 alpha. There were no significant regional differences in the responses to vasoconstrictive agents. Phenylephrine, xylazine and clonidine caused a dose-dependent contraction in the lymphatic preparations. Prazosin (10(-8) to 10(-7) M) inhibited the phenylephrine-induced vasoconstriction in a competitive manner. Xylazine-induced responses were inhibited competitively by yohimbine (10(-8) to 10(-7) M). These results suggest that both alpha-1 and alpha-2 adrenoceptors are located on the lymphatic smooth muscles of canine thoracic ducts. On the other hand, acetylcholine, isoproterenol, HIS, adenosine and ATP caused dose-dependent relaxations in canine thoracic ducts precontracted by 10(-5) M norepinephrine. The decreasing order of potency in the relaxant responses was as follows: acetylcholine much greater than isoproterenol much greater than adenosine not equal to HIS not equal to ATP. There were no significant regional differences in the relaxant responses to the agents. Procaterol, salbutamol, dobutamine and denopamine caused a dose-dependent relaxation of isolated canine thoracic ducts. Propranolol (10(-9) to 10(-8) M) inhibited procaterol- and dobutamine-induced vasorelaxations in a competitive manner. Metoprolol (10(-8) to 10(-7) M) inhibited only the dobutamine-induced vasorelaxation, but did not significantly influence the procaterol-induced response.(ABSTRACT TRUNCATED AT 250 WORDS)

Pressure within the thoracic duct modulates lymph composition

The amount of lymph received by the thoracic duct depends on each contributing organ's ability to produce interstitial fluid and generate a pressure differential moving lymph into the central lymphatic circulation. It has been reported that varying the pressure within the thoracic duct could alter each organ's contribution to thoracic duct flow. The thoracic duct above the diaphragm was cannulated to obtain lymph from the liver, gut, and lower body. Pressure within the thoracic duct was elevated serially by increasing the lymphatic cannula outflow height. This caused lymph protein concentration to increase while chyle concentration (measured by absorbance) decreased. The data demonstrate that as thoracic duct pressure increases, the percentage contribution of gut lymph flow (as represented by chyle concentration) decreases while the contribution of lymph originating within the liver (as indicated by higher protein concentration) increases. We conclude that pressure variation within the central lymphatic system affects the amount of lymph or edema fluid leaving any given organ.

The secretion of catecholamines, chromogranin A and neuropeptide Y from the adrenal medulla of the cat via the adrenolumbar vein and thoracic duct: different anatomic routes based on size

Secretion of the adrenal medulla was stimulated in nine cats by insulin-induced hypoglycemia. Levels of catecholamines (mol. wt 153-183), neuropeptide Y (mol. wt 4254) and chromogranin A (mol. wt 48,000) were measured in concurrently collected samples of adrenolumbar venous blood and thoracic duct lymph for up to 4 h following insulin administration. Insulin-induced hypoglycemia elicited an increase in the secretion of catecholamines, which reached peak levels in the adrenolumbar venous plasma at 1.5-2 h and in the lymph at 2.5 h. Although catecholamines were the most numerous measured molecules in the lymph, levels of norepinephrine and epinephrine were 75-250-fold less than those found in the adrenolumbar venous plasma. Neuropeptide Y in the adrenolumbar venous plasma reached peak levels between 1 and 1.5 h; at this time approximately 20% of the peak venous amount was detected in the lymph. Chromogranin A was found in approximately equal amounts in both plasma and lymph; the peak level in the plasma occurred at 1.5-2 h, while that in the lymph was reached at 2-3 h. We suggest that the size of a molecule influences the route it takes following exocytosis from the chromaffin vesicle. Smaller molecules such as catecholamines may pass directly into the circulation, while larger molecules such as chromogranin A may be temporarily sequestered in the interstitial space before passing into the lymph, and hence into the circulation.

Effect of whole-body pH changes on thoracic duct lymph flow in anesthetized sheep

Physiologic alterations of pH in vitro produce alterations of the oncotic pressure of both plasma and interstitial proteins, the effect being more marked in the latter. Therefore we postulated that by changing an animal's pH we could produce alterations in fluid distribution and affect the whole-body lymph flow rate. To test this hypothesis, we infused seven acutely nephrectomized anesthetized sheep with 2% body weight/volume isosmotic lactated Ringer's solution and bicarbonate (200 mEq) after a 30-minute control period. The fluid was infused over a 10-minute period with 20-minute recovery intervals. To another group of seven ewes, we infused the same volume of lactated Ringer's solution and hydrochloric acid (40 mEq). Throughout the experiment, we continuously measured arterial and venous pressures and lymph flow rate. Every 10 minutes we obtained samples for arterial pH, for hematocrit, and for plasma and lymph protein and osmolality. The infusion of bicarbonate was associated with a comparatively lower peak lymph flow rate (383% over baseline compared with 757% for acid infusion). Also the lymph flow rate after acid infusion started to increase approximately 5 minutes after the beginning of the infusion, as compared with approximately 10 minutes after the base infusion. Acid infusion did not increase arterial pressure, in contrast to the other infusions. The changes in pH obtained with the infusions were insignificant for the Ringer's infusion, +0.17 for the base, and -0.16 for the acid. The plasma/lymph protein concentration ratios at the end of the infusion were no different for acid or base: 112.4% +/- 4.4% and 101.9% +/- 5% (difference from control, mean +/- SEM) respectively (p greater than 0.1). In conclusion, minimal alterations of pH produced alterations in the cardiovascular and lymph flow rate responses to fluid challenge in anesthetized animals.

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).

Contribution of the liver to thoracic duct lymph flow in a motionless subject

To ascertain the contribution of the liver to thoracic duct lymph (TDL) flow in a resting subject, afferent hepatic blood flow was temporarily interrupted in dogs by placing an atraumatic clamp across the hepatoduodenal ligament containing the hepatic artery, portal vein and 80% of hepatic lymphatic drainage. To circumvent extrahepatic splanchnic venous sequestration, a side-to-side portacaval shunt (S-S-PCS) was constructed prior to interrupting blood flow. Portal venous pressure, cervical TDL flow, and total protein content were serially monitored. TDL and total protein after S-S-PCS was comparable to that recorded in dogs without celiotomy (0.60 +/- 0.17 ml/min and 3.4 +/- 0.5g/dl, respectively). Interruption of hepatic blood flow was associated with a fall in TDL flow (0.38 +/- 0.8ml; p less than 0.001) and protein content (2.8 +/- 0.7g/dl; p less than 0.01) and TDL/plasma protein ratio (0.58 +/- 0.7 to 0.48 +/- 0.05; p less than 0.01). These data suggest that in the absence of supplemental fluid administration or other exogenous stimulation, hepatic lymph contributes one-third of resting TDL flow.

Effects of outflow pressure on fetal lymph flow

The purpose of this study was to determine to what extent fetal thoracic duct lymph flow may be reduced by increases in fetal venous pressure. In pregnant sheep the fetal left thoracic lymph duct was catheterized at the base of the neck and this catheter was connected to a jugular-vein catheter so the lymph could spontaneously return to the fetal circulation. At 5 days after catheter implantation in nine unanesthetized fetuses at 133 +/- 1 (SE) days' gestation, lymph flow was measured by disconnecting the lymphatic catheter from that in the jugular vein and varying outflow pressure of the lymphatic catheter independent of venous pressure. Whenever outflow pressure was negative, lymph flow was independent of outflow pressure and averaged 0.66 +/- 0.05 ml/min. When outflow pressure of the left thoracic duct was increased above zero, lymph flow decreased linearly with outflow pressure and flow stopped at an outflow pressure of 11.5 +/- 0.6 mm Hg. At a normal venous pressure of 3 mm Hg, the lymph-flow sensitivity to venous pressure was such that a 1 mm Hg rise in venous pressure reduced lymph flow by 12.7% +/- 1.2%. Thus it appears that fetal lymph flow is very sensitive to outflow pressure and only moderate elevations in venous pressure potentially may lead to fetal edema.

The role of lymphatics in removing pleural liquid in discrete hydrothorax

The thoracic duct and right lymphatic duct of the dogs in the experimental group were ligated at the neck. Saline labelled with Evans blue was injected (10 ml.kg-1) into the pleural cavity. The colloid osmotic pressure of the saline was adjusted to be exactly equal to that of normal pleural liquid. The change in the volume of the liquid and the decrease of the marker were studied for 3 h. The dynamics of the pleural liquid were investigated. In the control group, the volume of the pleural liquid decreased at the rate of 1.31 ml.h-1.kg-1 body weight and 87% of it left via the lymphatics. With the ligation of the bilateral lymphatic ducts, the lymphatic removal rate decreased to about one tenth. This result shows that the hydrothorax leaves the pleural cavity mainly via the lymphatics.

[The mechanism of plasma protein release from skeletal muscles]

In anesthetized dogs with an open drainage of thoracic lymph duct, the resorption of the human plasma's 131-iodine-albumin from intercellular space of the hind-limb muscles in passive movements was performed by lymphatic system alone. The resorption was due to the gradients of hydrostatic pressure and concentration, to changes in the tissue pressure and to physiological shifts of the tissues.

Evaluation of the effects of lymph drainage by a thoracic duct fistula in experimental peritonitis

Previous studies suggest that systemic endotoxemia in peritonitis is mainly related to lymphatic transport via the thoracic duct. Rats with fecal peritonitis but with or without a lymph draining thoracic duct fistula were studied with reference to the concentrations of endogenously produced endotoxin in arterial plasma, hemodynamic parameters, organ blood flow, blood corpuscle parameters, glucose and lactate metabolism and survival. Lymph drainage significantly reduced the endotoxin concentrations in arterial plasma, but did not totally prevent systemic endotoxemia, and was related to maintained total peripheral vascular resistance. On the other hand, peritonitic rats without lymph drainage, and consequently higher endotoxin concentrations, had a significant fall in vascular resistance combined with a compensatory rise in cardiac output. Lymph drainage also contributed to a smaller decrease of platelet and leucocyte counts while no effect was observed on glucose metabolism. Despite the effect of lymph drainage on hemodynamic and hematologic responses no effect on survival time was recorded.

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.

Identification of beta-adrenergic sensitive adenylate cyclase in rat thoracic duct

The effect of L-isoproterenol on the 3',5'-cyclic adenosine monophosphate (cAMP) generating system in rat thoracic duct membranes was investigated in order to identify beta-adrenergic receptors. L-Isoproterenol elicited a dose-dependent stimulation of cAMP formation; L-noradrenaline was less effective than L-isoproterenol in stimulating cAMP increase, whereas L-phenylephrine was without important effects on cAMP levels. L-Propranolol, a selective antagonist of beta-adrenergic receptors, caused a dose-dependent decrease of the effects of L-isoproterenol. In contrast, the L-isoproterenol-elicited increase of cAMP was unaffected by the alpha-adrenergic and dopamine receptor-blocking agents phentolamine and haloperidol. These data indicate that L-isoproterenol stimulates cAMP formation in the rat thoracic duct by a specific interaction with beta-adrenergic receptors positively coupled to adenylate cyclase.

Lymph flow dynamics into the thoracic duct of the rat

Lymph flow into the thoracic duct of rats is reduced by 60% through immobilization with anesthesia. From this reduction, changes of the autonomic nervous activity by alpha-chloralose accounts for 20%. Pancuronium bromide blocking of the skeletal neuromuscular junction reduces lymph flow in the anesthetized rats by an additional 4%.

Angiotensin II infusion increases thoracic duct lymph flow in chronically catheterized sheep

Both pregnancy and estrogen administration are associated with a decrease in the systemic vasculature pressor response to angiotensin II infusion; however, the lymphatic vessel system response is not clear. In the present study we infused angiotensin II to nine nonpregnant splenectomized ewes with 0.1, 10, or 1,000 ng X kg-1 X min-1 for a 5-min period at each dose. At the lowest dose the mean arterial pressure increased from 10 to 20% over base line. At the highest dose, the left thoracic duct flow rate peaked at 361% 10 min after the infusion was started, whereas arterial pressure peaked at 183% of the control value. Peak lymph flow occurred 4-6 min after the maximal increase in mean systemic arterial pressure. Neither hematocrit nor venous pressure were altered at any of the doses administered. This suggests that the interstitial fluid space pressure remained unchanged and that the increase in lymph flow was not secondary to fluid transfer from the intravascular system. We postulate, therefore, that the effect of angiotensin II in the increase of lymph flow rate is by direct action on the lymphatic vessels themselves.

Angiogenesis and the formation of lymphaticlike channels in cultures of thoracic duct

Segments of rat thoracic duct cultured in plasma clot or in collagen gel produced microvascular and fibroblastic outgrowths. Lymphaticlike channels (LLC) with a highly attenuated endothelium, which was barely visible by light microscopy, were found in 8 out of 25 cultures (32%). Serial histologic sections revealed that the endothelium of the LLC was continuous with the intimal endothelium of the thoracic duct and was therefore of lymphatic origin. In addition to the LLC, vascular channels lined by a thick endothelium with hump-shaped, cross-sectional profiles were found in 10 cultures (40%). These channels were indistinguishable from the microvessels of blood vascular origin that formed in parallel cultures of rat aorta or periductal adipose tissue and were termed hematiclike channels (HLC). Contrary to the LLC, the HLC did not originate from the lymphatic endothelium of the thoracic duct. The frequent association of the HLC with the adventitia of the thoracic duct and with the surrounding adipose tissue suggested that they probably developed from the hematic microvessels of the periductal soft tissues.

Chylothorax in the dog and cat

The etiology, pathogenesis, and treatment of chylothorax are discussed in this article. A detailed discussion of thoracic duct anatomy, physiology, and methods of lymphangiography is included. The information presented is a review of previous literature, an update on recently completed studies, and speculation about where future research is needed.

Absorption of water-miscible forms of vitamin E in a patient with cholestasis and in thoracic duct-cannulated rats

Oral administration of vitamin E (100 mg tocopherol X kg-1 X day-1) as tocopheryl polyethylene glycol 1000 succinate (TPGS) to a child with congenital hepatic cholestasis (unresponsive to oral administration of dl-alpha-tocopheryl acetate) promoted an increase of tocopherol in plasma and adipose tissue while tocopheryl acetate emulsified with medium chain triglycerides and polysorbate 80 (MCT-E) did not. alpha-Tocopherol absorption, quantitated in thoracic duct-cannulated rats receiving intraduodenal infusions of soybean oil and saline, was similar for TPGS, MCT-E, and dl-alpha-tocopheryl acetate; gamma-tocopherol absorption from soybean oil was not affected by the presence of the supplemental alpha-tocopherol. Following bile duct ligation in one rat, TPGS promoted the absorption of alpha-tocopherol while absorption of gamma-tocopherol from soybean oil was decreased 30 fold, demonstrating that TPGS, which forms a micellar solution, delivers alpha-tocopherol through the unstirred water layer to enterocytes, while free tocopherol (alpha or gamma) absorption requires the presence of bile salts.

Thoracic duct lymph flow in pregnant sheep and response to blood volume expansion

Left thoracic duct lymph flow rate averaged 0.077 +/- 0.003 (SD) and 0.078 +/- 0.003 ml X min-1 X kg-1 in near-term pregnant and nonpregnant sheep (P greater than 0.5). Lymph and plasma protein concentrations were unaltered in the pregnant compared with the nonpregnant animals. The thoracic duct lymph flow responses to three serial intravenous infusions of lactated Ringer solution were essentially the same in the pregnant and nonpregnant animals. Blood volume and vascular pressure changes during and after volume loading were essentially the same in both groups. In addition, terbutaline administration after volume loading caused no change in thoracic duct lymph flow rates. Thus the present study suggests that basal lymph flow rates, lymphatic function, and vascular as well as interstitial compliances are largely unaltered late in pregnancy in the sheep. In addition, beta-mimetic stimulation with terbutaline does not appear to suppress lymph flow rate.