Anatomy and function of the vertebral column lymphatic network in mice

Cranial lymphatic vessels (LVs) are involved in the transport of fluids, macromolecules and central nervous system (CNS) immune responses. Little information about spinal LVs is available, because these delicate structures are embedded within vertebral tissues and difficult to visualize using traditional histology. Here we show an extended vertebral column LV network using three-dimensional imaging of decalcified iDISCO+-clarified spine segments. Vertebral LVs connect to peripheral sensory and sympathetic ganglia and form metameric vertebral circuits connecting to lymph nodes and the thoracic duct. They drain the epidural space and the dura mater around the spinal cord and associate with leukocytes. Vertebral LVs remodel extensively after spinal cord injury and VEGF-C-induced vertebral lymphangiogenesis exacerbates the inflammatory responses, T cell infiltration and demyelination following focal spinal cord lesion. Therefore, vertebral LVs add to skull meningeal LVs as gatekeepers of CNS immunity and may be potential targets to improve the maintenance and repair of spinal tissues.

Evaluation of the Efficacy of the Electrosurgical Bipolar Vessel Sealer (LigaSure) Devices in Sealing Lymphatic Vessels

Various sources of ultrasonic and thermal energy have been developed to facilitate blood vessel ligation. However, their efficacy in sealing lymphatics has not been clearly established to date. We hypothesized that the electrosurgical bipolar vessel sealer (EBVS) produces reliable and durable sealing of large lymphatic vessels in a porcine model. Thoracic ducts from 4 adult pigs were explanted and sealed at multiple levels by using 3 different EBVS devices: LigaSure Atlas, XTD, and V. Fifteen seals (5 per group) were analyzed for sealing time and visual quality. Seal burst strength was measured by using a graduated pressure saline injection system. Twelve intact seals also underwent a histologic analysis. The mean overall burst strength of the seals was 271 78 mm Hg (127 to 360 mm Hg). The burst pressures in the 3 groups were not statistically different. The overall mean time to achieve a seal was 5.12.2 seconds (3 to 10 seconds). Seals were achieved significantly faster in the V group (4.10.6 seconds) compared with the Atlas (6.32.3 seconds) and XTD (6.4 2.6 seconds) groups. Qualitative seal assessment revealed minimal sticking and charring, a favorable degree of seal tissue clarity, and desiccation in the 3 groups. Histologic analysis demonstrated a fusion of lymphovascular channels with a complete obliteration of the lumens. We demonstrated that the use of EBVS results in a fast and effective sealing of large porcine lymphatic vessels. The seals created by all 3 devices burst at markedly supraphysiologic intraluminal pressures. Ongoing randomized human trials may prove the clinical benefits of the routine use of EBVS devices for various tissue dissections.

Chylothorax associated with substernal goiter treated with transcervical thyroidectomy

BACKGROUND

Substernal goiters are frequently associated with compressive symptoms. Compression of the trachea and esophagus are common, whereas thoracic duct compression is a rare occurrence.

METHODS

We report a rare case of a 72-year-old woman with thoracic duct compression by a large substernal goiter that presented with shortness of breath. After undergoing thoracentesis multiple times, the patient was treated with thyroidectomy.

RESULTS

Transcervical thyroidectomy was performed without sternotomy. This led to resolution of her symptoms. Confirmation of chylothorax resolution was obtained with postoperative computed tomography of the chest.

CONCLUSION

Chylothorax is a rare sequela of substernal goiters. It can be managed with thyroidectomy. Sternotomy was avoided in this case.

[Changes of dynamics of the lymph production after the cannulation of the thoracic duct]

An adequate cannulation of the thoracic duct is always accompanied with appropriate dynamics of the lymph production. As a result, the daily output of lymph increases from 2.0 to 2.2 times during 4-5 days. To find out the reasons of the lymph production changes were examined 57 patients with acute purulent inflammatory diseases of abdominal and thoracic organs. It was determined that the lymph production change is conditioned by 2 factors: the first is the stopping of the flow into venous vessels via lympho-venous anastomosies of the thoracic duct, lymphatic trunks and large lymphatic vessels. It leads to a mobilization of the greater part of lymph in lymphatic vessels. The second is the speeding-up of lymph production.

Automated measurement of diameter and contraction waves of cannulated lymphatic microvessels

BACKGROUND

Studies of lymphatic function often employ collecting lymphatic vessels that exhibit large-amplitude, spontaneous contractions. Data from such preparations have been analyzed using cardiac pump analogies that require accurate determination of vascular dimensions, including external (OD) and internal (ID) diameters. These measurements would be facilitated by an accurate automated measurement system.

METHODS AND RESULTS

A computer-based diameter tracking system was developed specifically for lymphatic vessels, with advantages over previous automated systems. The system also permits continuous diameter tracking at two axial locations, enabling the measurement and analysis of contraction wave conduction. The method was validated using spontaneously contracting segments of rat thoracic duct which sometimes exhibited conducted contraction waves. In such preparations, conduction wave velocity was modulated by the axial flow rate and could be easily measured by the tracking system.

CONCLUSIONS

The method offers improvement and increased convenience over manual diameter measurements in lymphatic vessels, with little or no sacrifice in accuracy. It should be a useful tool for general studies of collecting lymphatic function as well as for the analysis of contraction wave conduction and coordination.

Lymphatic drainage of the peritoneal space: a pattern dependent on bowel lymphatics

BACKGROUND

Understanding lymph drainage patterns of the peritoneum could assist in staging and treatment of gastrointestinal and ovarian malignancies. Sentinel lymph nodes (SLNs) have been identified for solid organs and the pleural space. Our purpose was to determine whether the peritoneal space has a predictable lymph node drainage pattern.

METHODS

Rats received intraperitoneal injections of near-infrared (NIR) fluorescent tracers: namely, quantum dots (designed for retention in SLNs) or human serum albumin conjugated with IRDye800 (HSA800; designed for lymphatic flow beyond the SLN). A custom imaging system detected NIR fluorescence at 10 and 20 minutes and 1, 4, and 24 hours after injection. To determine the contribution of viscera to peritoneal lymphatic flow, additional cohorts received bowel resection before NIR tracer injection. Associations with appropriate controls were assessed with the chi(2) test.

RESULTS

Quantum dots drained to the celiac, superior mesenteric, and periportal lymph node groups. HSA800 drained to these same groups at early time points but continued flowing to the mediastinal lymph nodes via the thoracic duct. After bowel resection, both tracers were found in the thoracic, not abdominal, lymph node groups. Additionally, HSA800 was no longer found in the thoracic duct but in the anterior chest wall and diaphragmatic lymphatics.

CONCLUSIONS

The peritoneal space drains to the celiac, superior mesenteric, and periportal lymph node groups first. Lymph continues via the thoracic duct to the mediastinal lymph nodes. Bowel lymphatics are a key determinant of peritoneal lymph flow, because bowel resection shifts lymph flow directly to the intrathoracic lymph nodes via chest wall lymphatics.

Spontaneous healing of retroperitoneal chylous leakage following anterior lumbar spinal surgery: a case report and literature review

Cisterna chyli is prone to injury in any retroperitoneal surgery. However, retroperitoneal chylous leakage is a rare complication after anterior spinal surgery. To the best of our knowledge, only ten cases have been reported in the English literature. We present a case of a 49-year-old man who had lumbar metastasis and associated radiculopathy. He had transient retroperitoneal chylous leakage after anterior tumor decompression, interbody bony fusion, and instrumental fixation from L2 to L4. The leakage stopped spontaneously after we temporarily clamped the drain tube. Intraperitoneal ascites accumulation developed thereafter due to nutritional loss and impaired hepatic reserves. We gathered ten reported cases of chylous leak after anterior thoracolumbar or lumbar spinal surgery, and categorized all these cases into two groups, depending on the integrity of diaphragm. Six patients received anterior spinal surgery without diaphragm splitting. Postoperative chylous leak stopped after conservative treatment. Another five cases received diaphragm splitting in the interim of anterior spinal surgery. Chylous leakage stopped spontaneously in four patients. The remaining one had a chylothorax secondary to postop chyloretroperitoneum. It was resolved only after surgical intervention. In view of these cases, all the chylous leakage could be spontaneously closed without complications, except for one who had a secondary chylothorax and required thoracic duct ligation and chemopleurodesis. We conclude that intraoperative diaphragm splitting or incision does not increase the risk of secondary chylothorax if it was closed tightly at the end of the surgery and the chest tube drainage properly done.

Thoracic duct variations may complicate the anterior spine procedures

The aim of this study is to localize and document the anatomic features of the thoracic duct and its tributaries with special emphasis on the spinal surgery point of view. The thoracic ducts were dissected from nine formaldehyde-preserved male cadavers. The drainage patterns, diameter of the thoracic duct in upper, middle and lower thoracic segments, localization of main tributaries and morphologic features of cisterna chyli were determined. The thoracic duct was detected in all cadavers. The main tributaries were concentrated at upper thoracic (between third and fifth thoracic vertebrae) and lower thoracic segments (below the level of ninth thoracic vertebra) at the right side. However, the main lymphatic tributaries were drained into the thoracic duct only in the lower thoracic area (below the level of the tenth thoracic vertebra) at the left side. Two major anatomic variations were detected in the thoracic duct. In the first case, there were two different lymphatic drainage systems. In the second case, the thoracic duct was found as bifid at two different levels. In formaldehyde preservation, the dimensions of the soft tissues may change. For that reason, the dimensions were not discussed and they may not be a guide in surgery. Additionally, our study group is quite small. Larger series may be needed to define the anatomic variations. As a conclusion, anatomic variations of the thoracic duct are numerous and must be considered to avoid complications when doing surgery.

Chylothorax

Chylothorax is a rare complication of pulmonary resection. It requires prompt treatment, which is initially conservative. This treatment consists of drainage, nutritional support, and measures to diminish chyle flow. Surgical intervention is indicated when conservative management is ineffective. Delay in surgical intervention leads not only to serious metabolic, nutritional, and immunologic disturbances from the loss of chyle but also increases the risk for adhesion formation, loculation, organization, and infection of the chylothorax, making subsequent surgical attempts difficult and increasing postoperative morbidity and mortality. VATS provides a minimally invasive approach for the treatment of chylothorax complicating pulmonary resection. Clipping of the thoracic duct or chemical pleurodesis may be performed with minimal morbidity and mortality. Conservative treatment is expensive and fails in most patients who have high-output chylous fistulae. On the other hand, VATS is uniformly effective, is less expensive, and has low morbidity. Indeed, VATS is rapidly becoming the preferred approach for the management of chylothorax complicating pulmonary resection. The need to prevent the occurrence of a chylothorax by careful dissection techniques and liberal clipping of lymphatic vessels particularly in areas of high anatomic risk during the initial operation cannot be overemphasized.

Lymphography of the Thoracic Duct by Percutaneous Injection of Iohexol into the Popliteal Lymph Node of Dogs: Experimental Study and Clinical Application

OBJECTIVE

To evaluate the efficacy of percutaneous administration of iohexol into the popliteal lymph node as a non-invasive technique for thoracic duct lymphangiography in dogs.

STUDY DESIGN

Experimental study and clinical report.

ANIMALS

Normal adult dogs (n=4) and 1 dog with recurrent chylothorax.

METHODS

For the experimental study, 4 dogs (weight, 8.4-12.3 kg) had 5-10 mL iohexol injected percutaneously into 1 popliteal lymph node and then thoracic radiographs were taken. Popliteal lymph nodes were examined by histopathology 8 days later. One 25-kg dog with recurrent chylothorax had 25 mL iohexol injected into the right popliteal lymph node followed by thoracic radiography.

RESULTS

In experimental dogs, the thoracic duct was best visualized on thoracic radiographs after administration of 10 mL iohexol. Clinically, no abnormalities were identified in the injected limb and except for 1 dog that had large numbers of siderocytes and erythrophagocytic macrophages in the injected lymph node, the histopathologic findings in the other injected popliteal lymph nodes were not different from contralateral nodes. In the clinical case, the thoracic duct was visualized, but there was leakage of iohexol around the node.

CONCLUSION

The thoracic duct in dogs can be visualized by lymphography after percutaneous injection of iohexol (1 mL/kg at 2 mL/min) into the popliteal lymph node.

CLINICAL RELEVANCE

Percutaneous popliteal lymph node administration of iohexol should be considered as an alternative to mesenteric lymph node injection for radiographic identification of the thoracic duct in dogs.

Increased lymphatic flow in the thoracic duct during manipulative intervention

The thoracic pump and the abdominal pump are osteopathic manipulative (OM) lymphatic pump techniques frequently used by osteopathic physicians to treat patients with infections (eg, pneumonia, otitis media). Although there is a widely accepted belief among the osteopathic medical profession that increasing lymphatic flow is beneficial, no measurements of lymph flow during osteopathic manipulative treatment have been reported. The authors surgically instrumented five mongrel dogs to record lymphatic flow in the thoracic duct (TDF) and cardiac variables during three intervention protocols. After recovery from surgery, canine subjects were placed in a standing-support sling, and TDF, cardiac output, mean aortic blood pressure, and heart rate were recorded during two randomized 30-second sessions of manipulative intervention using the osteopathic thoracic pump and abdominal pump techniques on two successive days. Lymph flow in the thoracic duct increased from 1.57+/-0.20 mL x min(-1) to a peak TDF of 4.80+/-1.73 mL x min(-1) during abdominal pump, and from 1.20+/-0.41 mL x min(-1) to 3.45+/-1.61 mL x min(-1) during thoracic pump. Lymph flow in the thoracic duct and cardiac variables were also recorded for canine subjects during physical activity (ie, treadmill exercise at 3 miles per hour at 0% incline). During physical activity, TDF increased from 1.47+/-0.33 mL x min(-1) to 5.81+/-1.30 mL x min(-1). Although cardiac variables did not change significantly during manipulative intervention with lymphatic pump techniques, cardiac output and heart rate did increase during physical activity. The authors conclude that physical activity and manipulative intervention using thoracic pump and abdominal pump techniques produced net increases in TDF (P<.05).

[Functional anatomy of lymphangion]

This paper reviews the results of the studies performed mainly by the Russian anatomists on the functional anatomy of lymphangion as a structural and functional unit of lymphatic vessel. One of the peculiar features of functional anatomy of lymphangion is the heterogeneity of its structures (myocytes, endothelium, blood supply and innervation). The functional heterogeneity of different lymphangions, which depends on the local differences in the combination of lymph flow factors, was demonstrated. The role of lymphatic vessels is discussed on the basis of significance of lymphangion in active lymph transport. This is demonstrated by the multiple correlations between lymphangion structure, rate and type of its contractions, length of thoracic duct lymphangions and contraction type (peristaltic, rhythmic), number of lymphangions of thoracic duct and its type (presence of collaterals), form of individual variability of thoracic duct and its myoarchitecture, body mass and lymphangion volume in various animals and at different stages of ontogenesis.

One technique, two approaches, and results: thoracic duct cannulation in small laboratory animals

Experimental studies in immunology, pharmacology, or hematology require the sampling of the total thoracic duct lymph in awake and unrestrained rats or mice. Several approaches have been described for cannulation of the thoracic duct, but they are characterized by a modest reproducibility and a low lymph flow rate. An improved technique for obtaining thoracic duct lymph is described here, emphasizing the similarities and differences concerning both rats and mice (average weights of 305 and 15 g, respectively). Rats yielded a mean of 55.6 ml/day thoracic duct lymph, while lymph output in mice reached unexpected volumes of 29.3 ml/day. The use of an operating microscope and silicone cannula, and maintenance of mobility of the animals during lymph collection, offer a reliable method for a high and constant output of thoracic duct lymph. Relevant aspects of the murine thoracic duct anatomy are also identified.

Molecular and functional analyses of the contractile apparatus in lymphatic muscle

Lymphatics are necessary for the generation and regulation of lymph flow. Lymphatics use phasic contractions and extrinsic compressions to generate flow; tonic contractions alter resistance. Lymphatic muscle exhibits important differences from typical vascular smooth muscle. In this study, the thoracic duct exhibited significant functional differences from mesenteric lymphatics. To understand the molecular basis for these differences, we examined the profiles of contractile proteins and their messages in mesenteric lymphatics, thoracic duct, and arterioles. Results demonstrated that mesenteric lymphatics express only SMB smooth muscle myosin heavy chain (SM-MHC), whereas thoracic duct and arterioles expressed both SMA and SMB isoforms. Both SM1 and SM2 isoforms of SM-MHC were detected in arterioles and mesenteric and thoracic lymphatics. In addition, the fetal cardiac/skeletal slow-twitch muscle-specific beta-MHC message was detected only in mesenteric lymphatics. All four actin messages, cardiac alpha-actin, vascular alpha-actin, enteric gamma-actin, and skeletal alpha-actin, were present in both mesenteric lymphatics and arterioles. However, in thoracic duct, predominantly cardiac alpha-actin and vascular alpha-actin were found. Western blot and immunohistochemical analyses corroborated the mRNA studies. However, in arterioles only vascular alpha-actin protein was detected. These data indicate that lymphatics display genotypic and phenotypic characteristics of vascular, cardiac, and visceral myocytes, which are needed to fulfill the unique roles of the lymphatic system.

Inhibition of the active lymph pump by flow in rat mesenteric lymphatics and thoracic duct

There are only a few reports of the influence of imposed flow on an active lymph pump under conditions of controlled intraluminal pressure. Thus, the mechanisms are not clearly defined. Rat mesenteric lymphatics and thoracic ducts were isolated, cannulated and pressurized. Input and output pressures were adjusted to impose various flows. Lymphatic systolic and diastolic diameters were measured and used to determine contraction frequency and pump flow indices. Imposed flow inhibited the active lymph pump in both mesenteric lymphatics and in the thoracic duct. The active pump of the thoracic duct appeared more sensitive to flow than did the active pump of the mesenteric lymphatics. Imposed flow reduced the frequency and amplitude of the contractions and accordingly the active pump flow. Flow-induced inhibition of the active lymph pump followed two temporal patterns. The first pattern was a rapidly developing inhibition of contraction frequency. Upon imposition of flow, the contraction frequency immediately fell and then partially recovered over time during continued flow. This effect was dependent on the magnitude of imposed flow, but did not depend on the direction of flow. The effect also depended upon the rate of change in the direction of flow. The second pattern was a slowly developing reduction of the amplitude of the lymphatic contractions, which increased over time during continued flow. The inhibition of contraction amplitude was dependent on the direction of the imposed flow, but independent of the magnitude of flow. Nitric oxide was partly but not completely responsible for the influence of flow on the mesenteric lymph pump. Exposure to NO mimicked the effects of flow, and inhibition of the NO synthase by N (G)-monomethyl-L-arginine attenuated but did not completely abolish the effects of flow.

Gut intraepithelial lymphocyte development

CD8alphabeta(+) and CD4(+) intraepithelial lymphocytes, the progeny of double-positive thymocytes, are oligoclonal T-cell populations that have accumulated in the gut wall as the result of repeated antigenic stimulations, which lead to rounds of traffic through the lymph/blood circuit ending in an alpha4beta7-integrin-driven homing all along the gut mucosa. In contrast, CD8alphaalpha(+) intraepithelial lymphocytes, which may be TCRgammadelta(+) or alphabeta(+), result in part from local differentiation in the gut, but studies comparing euthymic and athymic mice suggest a thymic double-negative origin for many of them.

Histochemical analysis of lymphatic endothelial cells in lymphostasis

The ultrastructure of endothelial cells of intestinal lymphatics and the thoracic duct (TD) and the relation to lymphostasis were examined in rats and monkeys. Localization of 5'-nucleotidase (5'-Nase) and endothelial nitric oxide synthase (eNOS) was studied. In normal lymphatic endothelial cells, 5'-Nase reaction product was evenly deposited on the cell surface in vivo and on cultured TD endothelial cells (TDECs), whereas eNOS was evenly distributed throughout the nucleus and cytoplasm. TDECs had a long filamentous process extending towards the subendothelial extracellular matrix but became flat and regular within 30-40 minutes after gastric perfusion with olive oil. According to their electron-density, two types of cells were found in the TD endothelial layer. The cells with low electron-density exhibited stronger 5'-Nase activity. Valves were bicuspid formations and the valvular endothelial surface of the convex side showed weaker 5'-Nase activity than the concave side. During TD blockage-induced lymphostasis in rats, the 5'-Nase product was almost not discernible in the TDECs within 2 weeks. Larger vesicles were found in the endothelial cytoplasm of the ligated TD. Their number decreased after 6-12 weeks. The small intestinal lymphatics in the mucosa and submucosa were dilated, with numerous open intercellular junctions. The endothelial lining appeared to have reduced activities for 5'-Nase and eNOS in 9 of 11 experimental animals. The results indicated that the inability of the open intercellular junctions, normally working as one-way endothelial flap valves, may be a key morphological feature after TD blockage. Reduced eNOS and 5'-Nase may functionally influence contractile activity and transport capability of the lymphatic vessels in the lymphostasis.

Flow in lymphatic networks: interaction between hepatic and intestinal lymph vessels

OBJECTIVE

Lymph from both the liver and intestine flows into the cisterna chyli. We hypothesized that increasing liver lymph flow would increase cisterna chyli pressure and, thereby, decrease intestinal lymph flow, potentiating intestinal edema formation.

METHODS

Anesthetized dogs were instrumented to measure and manipulate portal vein pressure and cisterna chyli pressure. The effects of directly increasing portal pressure with and without directly increasing cisterna chyli pressure on intestinal wet-to-dry ratio and intestinal ascites formation rate were determined. Target values for portal and cisterna chyli pressures were determined following elevation of inferior vena caval pressure to levels seen in patients with obstructive caval disease.

RESULTS

Direct elevation of portal pressure (P(port)) alone to 17.5 mm Hg caused a significant increase in intestinal wet-to-dry ratio (3.98 +/- 0.24 vs. 3.40 +/- 0.43) and the rate of ascites formation (0.36 +/- 0.12 vs. 0.05 +/- 0.03 mL/g dry wt/h). Simultaneous direct elevation of cisterna chyli pressure to 6.0 mm Hg and P(port) to 17.5 mm Hg caused further increases in intestinal wet-to-dry ratio (5.52 +/- 1.20) and ascites formation (0.57 +/- 0.11 mL/g dry wt./h).

CONCLUSIONS

Inferior vena caval hypertension increases liver lymph flow that elevates cisterna chyli pressure, which inhibits intestinal lymph flow and augments intestinal edema formation.

Correction of lymph circulation during immediate hypersensitivity reaction

We measured lymph flow rate in the thoracic lymphatic duct of dogs with anaphylactic shock receiving mono- or combination therapy with norepinephrine and hydrocortisone. Intensification of lymph circulation improved resorption and transport of metabolic products from the interstitial space through lymphatic vessels and stimulated exchange processes in the blood and tissues during allergic alterations.

Mechanical characteristics of the canine thoracic duct: what are the driving forces of the lymph flow?

This study is designed to better understand the mode of lymph transport, particularly through the extrinsic pumping by external compression of the lymph vessel. The pressure-diameter relationship of lymphatic segments isolated from the canine thoracic duct was examined using a laser optical micrometer measurement system. Results revealed that the thoracic duct displayed a high extensibility or compliance in the physiological pressure range, yet became progressively less so with increasing internal pressure. The calculated incremental circumferential modulus of the thoracic duct under physiological pressure (range of 2 to 6 cm H2O) showed values ranging from 1.2 x 10(4) to 3.61 x 10(5) dyn/cm2. At a pressure of 35 cm H2O, the modulus reached a limiting value of approximately 6.0 x 10(6) dyn/cm2. In the physiological pressure range, the relative wall thickness (h/R0) of the canine thoracic duct was approximately 3.5%, which was much lower than that reported for canine arterial segments and similar in value to that of the canine jugular vein. In conclusion, the pressure-diameter curve of the canine thoracic duct was shown to resemble that of venous vessels. However, the circumferential elastic modulus of the thoracic duct wall was lower than the moduli of veins, proving that lymphatics are more compliant than veins. This suggests lymph flow in the thoracic duct may be better promoted by external compression of the lymphatic vessel.

Effects of VEGF on Ca(2+)-transient in cultured lymphatic endothelial cells and mechanical activity of isolated lymph vessels

We investigated the effects of vascular endothelial growth factor (VEGF(165)) on [Ca(2+)](i)-transient in cultured lymphatic endothelial cells (LEC) and mechanical activity of isolated dog thoracic ducts. VEGF (0.1-10 ng/ml) caused a dose-dependent increase of the [Ca(2+)](i) in LEC. Pretreatment with 10(-5) M genistein or 5x10(-6) M herbimycin A produced a significant reduction of the VEGF-induced [Ca(2+)](i)-transient. In the presence of 10(-6) M thapsigargin, VEGF caused no significant effect on the [Ca(2+)](i)-transient. Pretreatment with Ca(2+)-free solution containing 0.1 mM EGTA produced no significant effect on the peak increase of [Ca(2+)](i) induced by 0.1 or 10 ng/ml VEGF, but significantly depressed the sustained part of [Ca(2+)](i) observed at the higher concentration of VEGF. The VEGF (0.1-10 ng/ml) caused a significant dilation of the isolated lymph vessels with intact endothelium, which were precontracted with U46,619. The 10 ng/ml VEGF-induced dilation was significantly reduced by 3 x 10(-5) M N(omega)-nitro-L-arginine methyl ester (L-NAME). The action of L-NAME was inhibited by the simultaneous application of 10(-3) M L-arginine. Mechanical rubbing of the endothelium also caused significant inhibition of the VEGF-induced dilation. The findings suggest that VEGF(165) may activate the receptor-related tyrosine kinase and cause the release of Ca(2+) from the inositol 1,4, 5-triphosphate-sensitive intracellular Ca(2+) stores in LEC. VEGF(165) also produces endothelium-dependent nitric oxide-mediated dilation of the precontracted isolated lymph vessels.

Thoracic duct lymph flow and its driving pressure in anesthetized sheep

We examined the relationship between thoracic duct lymph flow (TDF) and its driving pressure (DP) in six anesthetized sheep. DP was determined as the thoracic duct pressure (TDP) minus the innominate vein pressure (VP). TDF was measured using an ultrasound transit-time flow meter, placing a flow probe beside the caudal mediastinal lymph node. TDP was measured with a fine needle inserted near the flow probe. TDP increased linearly together with an increase in VP after balloon inflation in the cranial vena cava with a TDP/VP ratio of 0.79. DP decreased, therefore, with an increase in VP and this decrease in DP correlated directly with a fall in TDF. After rapid i.v. fluid infusion, TDF increased but DP varied among the six sheep. Nonetheless, after balloon inflation with expanded volume (i.e., i.v. fluid infusion), DP and TDF were positively correlated. We conclude that DP is the main factor determining TDF when VP rises in conjunction with increased lymph production.

Analysis of thoracic duct flow waves using fast Fourier transform in sheep

We measured the lymph flow of the thoracic duct using an ultrasound transit-time flowmeter and then analyzed the obtained flow signals by fast Fourier transform. We found that the wave form included a low frequency component (approximately 0.1 Hz) as well as high frequency components which represented cordiac pulsation and respiratory movement. The low frequency component signified an intrinsic thoracic duct pulsation. When venous outflow pressure was increased, the frequency of the thoracic duct pulsation increased, whereas the frequencies of cardiac pulsation and respiratory movement were unchanged. These findings suggest that thoracic duct pulsation is independent of cardiac pulsation and respiratory movement.

Electrical stimulation-induced alpha1- and alpha2-adrenoceptors-mediated contraction in isolated dog thoracic ducts

The electrical stimulation-induced responses of isolated dog thoracic ducts were investigated using an organ bath technique. Electrical stimulation (0.7 ms in pulse width, 25 V in nominal voltage, 10 s in duration time, 1-32 Hz at frequency) produced frequency-related contractions in the lymphatic preparations. The contractions were abolished by pretreatment with tetrodotoxin (10(-7) M), guanethidine (10(-7), 10(-6) M), and bretylium (10(-7), 10(-6) M). Cocaine (10(-6) M) significantly potentiated the electrical stimulation-induced contractions. Phentolamine (10(-8)-10(-5) M), prazosin (10(-8)-10(-5) M), bunazosin (10(-6), 10(-5) M), yohimbine (10(-8)-10(-6) M) and rauwolscine (10(-8)-10(-6) M) also dose-dependently reduced the contractions. On the other hand, propranolol (10(-8)-10(-6) M), atropine (10(-6) M), hexamethonium (10(-6) M), aspirin (3 x 10(-5) M), N(omega)-nitro-L-arginine methyl ester (L-NAME) (3 x 10(-5) M) and L-NAME (3 x 10(-5) M) + L-arginine (10(-4) M) caused no significant effect on electrical stimulation-induced contractions. No significant difference in the electrical stimulation-induced responses was observed between the lymphatic preparations with and without an intact endothelium. The electrical stimulation caused only a small contraction with no relaxation in the thoracic duct preparation precontracted with 10(-8) M U46619. The small contraction was abolished by 10(-5) M phentolamine. These findings suggest that there exists alpha1- and alpha2-adrenoceptors-mediated excitatory innervation, but no NO-ergic inhibitory nerve fiber in dog thoracic ducts.

Lymphatic drainage reduces intestinal edema and fluid loss

Lymphatic vessels are important in removing excess fluid from the intestine and transporting the fluid to veins in the neck. However, in some diseases, neck vein pressure is increased and the high pressure may slow lymph flow. This study was to test the hypothesis that lymphatic clearance of fluid from the intestine may be increased by draining the lymphatics. Inflatable cuffs were used to increase neck vein pressure and portal venous pressure in anesthetized sheep. The lymphatic vessel from one segment of small intestine was cannulated and drained. The lymphatic vessel to a control segment of intestine was left intact. After 90 min. we found significantly less fluid in the lumen of the drained vs. control segments (7.4 +/- 3.1 (SD) ml vs 11.5 +/- 4.7 ml per gram dry tissue, respectively). Also we found significantly less tissue fluid in the drained vs control segments (5.3 +/- 0.3 ml/g vs 6.0 +/- 0.4 ml/g). The findings support the hypothesis that external diversion of lymph in the presence of an elevated central venous pressure reduces edema formation.

Lymph flow pattern in the intact thoracic duct in sheep

1. To study the lymph flow dynamics in the intact thoracic duct, we applied an ultrasound transit-time flow probe in seven anaesthetized and four unanaesthetized adult sheep (approximately 60 kg). In unanaesthetized non-fasting animals we found that lymph flow in the thoracic duct was always regular pulsatile (pulsation frequency, 5.2 +/- 0.8 min-1) with no relation to heart or respiratory activity. At baseline the peak level of the thoracic duct pulse flow was 11.6-20.7 ml min-1 with a nadir of 0-3.6 ml min-1. Mean lymph flow was 5.4 +/- 3.1 ml min-1. The flow pattern of lymph in the thoracic duct was essentially the same in the anaesthetized animals. 2. In both the anaesthetized and unanaesthetized animals, the lymph flow response to a stepwise increase in the outflow venous pressure showed interindividual variation. Some were sensitive to any increase in outflow venous pressure, but others were resistant in that lymph flow did not decrease until outflow venous pressure was increased to higher levels. This resistance was also observed in the high lymph flow condition produced by fluid infusion in the anaesthetized animal and mechanical constriction of the caudal vena cava in the unaesthetized animals. Pulsation frequency of the thoracic duct flow initially increased and then decreased with a stepwise increase in the outflow venous pressure. This initial increase might be a compensatory response to maintain lymph flow against elevated outflow venous pressure. 3. To test the effect of long-term outflow venous pressure elevation in unanaesthetized sheep, outflow venous pressure was increased by inflation of a cuff around the cranial vena cava for 1, 5 or 25 h. The cuff was inflated to a level where lymph flow was reduced. Lymph flow remained low or decreased further during the entire cuff-inflation period. We calculated the lymph debt caused by the outflow venous pressure elevation and the amount 'repaid' when venous pressure returned to normal. Lymph debt for 25 h was 6400 ml but only 200 ml was repaid. Since we observed no visible oedema formation in the lower body of the sheep, the non-colloidal components of the lymph must have been reabsorbed into the bloodstream, most likely in the lymph nodes.

Drainage of CSF through lymphatic pathways and arachnoid villi in sheep: measurement of 125I-albumin clearance

We investigated lymphatic drainage pathways of the central nervous system in conscious sheep and quantified the clearance of a cerebrospinal fluid (CSF) tracer into lymph and blood. In the first group of studies, 125I-HSA was injected into the lateral ventricles of the brain or into lumbar CSF and after 6 h, various lymph nodes and tissues were excised and counted for radioactivity. Multiple lymphatic drainage pathways of cranial CSF existed in the head and neck region defined by elevated 125I-HSA in the retropharyngeal/cervical, thymic, pre-auricular and submandibular nodes. Implicated in spinal CSF drainage were mainly the lumbar and intercostal nodes. In a second group of experiments, multiple cervical vessels and the thoracic duct were cannulated and lymph diverted from the animals. Transport of tracer through arachnoid villi was taken from recoveries in venous blood. Following intraventricular administration, the 6 h recoveries of 125I-HSA in the lymph (sum of cervical and thoracic duct) and blood were 8.2% +/- 3.0 and 12.5% +/- 4.5 respectively and at 22 h, 25.1% +/- 6.9 and 20.8% +/- 4.1 respectively. When 125I-HSA was injected into lumbar CSF, the 6 h recoveries of tracer in thoracic duct and blood were 11.6% +/- 2.7 and 16.3% +/- 3.7 respectively. Total lymph and blood recoveries were not significantly different in any experiment. We conclude that the clearance of 125I-HSA from the CSF is almost equally distributed between lymphatic and arachnoid villi pathways.

Thoracic duct function in fetal, newborn, and adult sheep

We measured thoracic duct lymph flow rate versus outflow pressure in 7 chronically catheterized adult sheep and in 6 newborn lambs and compared our results to data previously obtained from 10 fetal sheep. In fetal sheep the thoracic duct lymph flow rate was 34.5 +/- 17.2 ml/hr or 11.7 +/- 6.0 ml/kg/hr. Fetal thoracic duct lymph flow deviated from baseline between 8 and 12 torr outflow pressure and lymph stopped at 18 +/- 2.5 torr. In newborn lambs the thoracic duct lymph flow rate was 49.5 +/- 22.0 ml/hr or 7.4 +/- 2.5 ml/kg/hr. The range of outflow pressures over which newborn lymph flow deviated from baseline was between 15 and 18 torr and lymph flow stopped at 26.2 +/- 6.4 torr. Adult sheep thoracic duct lymph flow rate was 130 +/- 74 ml/hr or 2.3 +/- 1.3 ml/kg/hr. Adult lymph flow deviated from baseline between 25 and 35 torr and stopped at an outflow pressure of 41.7 +/- 6.7 torr. The ability of the thoracic duct to return lymph against an outflow pressure improves with maturation. However, lymph flow rate corrected for body weight is greatest in immature animals. The higher corrected lymph flow rate in conjunction with the decreased ability to pump against an outflow pressure may help account for immature animals predisposition for edema.

[The valvular apparatus and tissue organization of the endothelium of the thoracic duct]

The structure of ostial valves and valves located along the thoracic duct and of its branches ostial valves and right lymphatic duct ostial valves were studied in 30 experimental outbred dogs and 46 cats. Cryodestruction of thoracic duct was performed in 28 outbred cats. 1, 3, 7 and 14 days later perfusive fixation with intercellular borders impregnation was carried out with simultaneous examination of intact regions of intravalvular segments, cisterna chyli and area of thoracic duct trunks connection with valvular surfaces. Tissue organization in ageing was studied using the intervalvular segment of old animals. Specimens were studied by means of scanning electron microscopy and film preparations of endothelium. Valves, located along the thoracic duct length are bicuspid formations, while ostial ones are falciform and cuneiform respectively in 80 and 20%. Endotheliocytes of cuspids are characterized with high content of microfilaments bundles in the cytoplasm and low content of microvesicles. Cells of the valvular free margin cross the cuspid edge and have adaptive changes preventing their desquamation: fusiform shape, long basal processes and bundles of microfilaments in the cytoplasm. Peculiar "pericyte-like" cells alike with myofibroblasts lie deep in the cuspid thickness close to the sinusal venous side. Fascicles of the duct smooth myocytes reach the base of the valve. Besides, in the ostial valve stroma there is elastic membrane, better displayed along the cuspid venous side. Increased polymorphism and changes of the endotheliocytes metric characteristics were demonstrated in the zones of turbulent lymph flow. Analysis of the newly formed endothelium tissue mosaics allows to reveal mechanisms of monolayer repair: spreading and migration of endotheliocytes on the first day, their proliferation within three days, desquamation of newly formed endotheliocytes and spreading of adjacent cells on later stages.

Increased abdominal lymph flow increases lung lymphatic outflow pressure in sheep

We tested the hypothesis that increased lymph flow from the abdominal organs would increase the pressure within the thoracic duct at the thoracic duct-lung lymphatic junction. Cannulas were placed into the thoracic duct via the caudal mediastinal (lung) node efferent lymphatics in 4 sheep. After the sheep recovered from the surgery, we monitored the thoracic duct pressure with pressure transducers. To increase lymph flow from the lower body, we infused Ringers solution (59 +/- 19 [mean +/- SD] ml/kg body weight in 30 min.) intravenously into the sheep and we inflated a balloon in the inferior vena cava. This technique causes substantial increases in lymph flow from the lower body (mainly from the liver and intestines) through the thoracic duct. During the infusions, the thoracic duct pressure increased significantly from 4.1 +/- 2.9 cm H2O (baseline) to 6.8 +/- 1.7 cm H2O. The neck vein pressure (pressure at the outflow of the thoracic duct) did not increase from baseline (3.0 +/- 2.6 cm H2O). Thus our results support the hypotheses that increased flow through the thoracic duct causes increased thoracic duct pressure.

Regeneration of the endothelium in the canine and feline thoracic duct

Recent improvements in microsurgical techniques on lymphatic vessels facilitated the treatment of lymphoedema. But it is becoming clear that a successful treatment of lymphatic disease has to be based on knowledge of ongoing processes. Particularly, one of the important and unclear issue is cellular mechanisms of lymphatic regeneration. The regeneration of endothelial and the smooth muscle cells of the thoracic duct has been experimentally tested in vivo. The canine and feline thoracic duct was cryo-injured using 3 mm-based copper rod. Damaged endothelial cells remained attached to the substrate and lost unthrombogenecy within 48 hr. Adjacent EC restored the defect within 3 days by migration and proliferation. We observed that on the first day, the endothelial monolayer included some elongated multinuclear cells with blind silver lines whereas, on the third day, they were replaced by a population of smaller ECs with numerous mitoses. Organization of the monolayer was restituted within 7 days. The newly formed endothelium was similar to regenerating endothelium of arteries. In general, the clot that appeared at the zone of injury on the second day was dissolved by the third day. Occasionally, the dense polymorphic clot adhered to the wall and caused a delay in reendothelisation. Complete restitution of the tunica media which involved migration and proliferation mechanisms accompanied the endothelium regeneration.

Direct lymphatic drainage from the esophagus into the thoracic duct

The lymphatic vessels from around the esophagus which drain into the thoracic duct were identified macroscopically and histologically in 106 cadavers. Direct lymphatic drainage to the duct was macroscopically demonstrated by 84 vessels in 46 cases (43.4%). In 23 cases (19.8%), large collecting vessels arose from the thoracic esophagus and opened directly into the duct. In most of these cases (15/23) these lymphatic connections were found at the levels of the 1st-3rd or 6th-8th thoracic vertebrae. Histologic study revealed that two vessels originated from the fine lymphatic plexus in the esophageal adventita, which showed monocytic infiltration. In 11 of the 23 cases, an intercalated node was found along the thoracic duct. The results suggest that lymph drains rapidly into the systemic circulation via the thoracic duct. In view of the clinical applications in esophageal carcinoma, previous accounts of the extramural esophageal lymphatics concerned in direct drainage are discussed.

[The contractile activity of the lymphatic vessels in rats after head-down tilt exposure]

After antiorthostatic attitude of rats during 12 days, the contractile activity of their isolated lymphangions of the thoracic duct was studied. The amplitude of contractions was found to be decreased as well as the effects of serotonine, histamine, and acetylcholine, whereas that of adrenaline increased. The latter finding suggests enhancing of the activity of lymphatic vessels' adrenergic structures in antiorthostatic.

Chylothorax

The management of chylothorax requires a thorough understanding of the anatomy and pathophysiology of the major thoracic lymphatics, prompt diagnosis, and (with rare exception) conservative management, including evacuation of the pleural space, nutritional support, and measures to reduce chyle production. A minority of chylothoraces will fail to resolve with these measures. Surgical intervention is then required to prevent chronic metabolic deterioration and death.

Pharmacologic properties of Daflon 500 mg

AIMS AND METHODS

Some pharmacologic activities of a micronized flavonoid complex consisting of 90% diosmin + 10% hesperidin (Daflon 500 mg*) have been investigated by use of various experimental models: (1) interference with mechanisms of edema (synthesis of arachidonic acid derivatives, microvascular hyperpermeability induced by bradykinin, ischemia, or streptozotocin), (2) interference with lymphatic drainage (thoracic duct fistula in the dog).

RESULTS

Daflon 500 mg inhibited prostaglandin E2 (PGE2) and thromboxane A2 (TxA2) synthesis during a one-month oral daily treatment (100 mg.kg-1.day-1) in the rat, after induction of chronic inflammation by subcutaneous implantation of sponge fragments. Microvascular hyperpermeability induced by bradykinin or ischemia in the rat cremaster muscle was reduced after an oral treatment with Daflon 500 mg (100 mg.kg-1 twice daily). Microvascular hyperpermeability of the streptozotocin-induced diabetic rat was antagonized when Daflon 500 mg (300 mg.kg-1 once daily) was given orally as a preventive treatment. In the anesthetized dog, an increase in lymphatic flow, correlated with administered doses, was observed after IV injection of Daflon 500 mg. Lymphatic flow was maximal twenty minutes after injection of the drug (12.5 mg.kg-1) and was three times higher than the basal flow.

CONCLUSION

The protective effect of Daflon 500 mg against the formation of perivascular edema and its therapeutic value in the treatment of venous stasis could be explained by its inhibitory activity on the inflammatory process or ischemia-induced hyperpermeability and by its stimulatory effect on the pulsatile activity of lymphatic vessels.

Chylothorax: an update

Chylothorax is occasionally found in malignant disease and following sympathectomy, but is seen more frequently after cardiothoracic surgery. The varied anatomy of the thoracic duct, limited individual experience and a lack of appreciation of the factors indicating surgical intervention have led to controversy regarding its optimal management. This article reviews historical aspects, clinical features and guidelines for conservative and surgical management.

Maximal lymph flow in the ovine fetus

OBJECTIVE

This study was designed to determine the maximal left thoracic duct lymph flow rate in late-gestation ovine fetuses.

STUDY DESIGN

Chronically catheterized sheep fetuses (n = 8) with indwelling left thoracic lymph duct and vascular catheters were studied > or = 5 days after surgery at 136 +/- 1 (SE) days' gestation. To increase lymph flow rate, 4 L of warm lactated Ringer's solution were infused intravenously into the fetus over 4 hours, because this causes mild edema as determined ultrasonographically.

RESULTS

During a 1-hour preinfusion period lymph flow rate was 0.53 +/- 0.06 ml/min. During the infusion increases occurred in fetal arterial (7.6 +/- 1.0 mm Hg) and venous (2.4 +/- 0.3 mm Hg) pressures (p < 0.001). Lymph flow rate increased and reached a plateau after 1 hour at 339% +/- 30% of preinfusion values (p < 0.001). When the infusion was terminated, fetal arterial and venous pressures rapidly returned to preinfusion levels. Lymph flow rate gradually decreased during the first 30 minutes and stabilized at 97% +/- 17% above control during the subsequent 30 minutes. Analysis of lymph flow rate as a function of outflow pressure revealed that the increases in flow occurred because of an upward shift in the plateau flow rate with no change in the stop-flow pressure.

CONCLUSIONS

(1) Fetal left thoracic duct lymph flow rate can increase significantly above basal values and therefore is an important safety factor against fetal edema formation. (2) The maximal lymph flow rate appears to be 3.4 times normal when venous pressure is elevated and two times normal when venous pressure is normal.

Evaluation of thoracic duct healing after experimental laceration and transection

Healing of the thoracic duct (TD) was evaluated clinically and histologically in six healthy dogs. A 2.5 cm longitudinal laceration of the caudal TD was created in three dogs and the caudal TD was completely transected in three other dogs. The site of the defect was identified by placing one 4-0 stainless steel suture in the tissue adjacent to the TD defect. All dogs developed a chylous effusion confirmed by biochemical analysis. By five days after surgery in dogs with TD lacerations, and by 10 days after surgery in dogs with TD transections, thoracic effusion had ceased. Lymphangiography, performed seven days after resolution of thoracic effusion, showed TD patency only in the dogs with TD lacerations. The TD did not appear to be patent in dogs with TD transections. Histologically, in dogs with TD lacerations, one moderately dilated lymphatic vessel was seen at the surgical site in one animal and the thoracic duct and other lymphatics in the two other dogs appeared normal. Minimal perivascular accumulations of neutrophils, macrophages, and lymphocytes were present adjacent to two lymphatics in one animal. A mild increase in fibrous connective tissue and neovascularization was present in the adjacent subpleura. In dogs with complete transections, three to six dilated lymphatics were present at the transection site. Mild thickening of the tunica media was present in one thoracic duct, associated with a "J"-shaped area of condensed collagen, presumed to be a collapsed thoracic duct in one animal. Mild to moderate accumulations of macrophages, lymphocytes, and moderate neovascularization was present in the surrounding tissue, separating it from the underlying connective tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal lymphatic pressure increases during intravenous infusions in awake sheep

Intravenous fluid infusions cause increased venous pressure and increased lymph flow throughout the body. Together the increased lymph flow and increased venous pressure (the outflow pressure to the lymphatic system) should increase the pressure within the postnodal intestinal lymphatics. To test this, we measured the pressure in postnodal intestinal lymphatics and the neck vein pressure in five awake sheep. At baseline, the neck vein pressure was 1.2 +/- 1.5 (SD) cmH2O and the lymphatic pressure was 12.5 +/- 1.7 cmH2O. When we infused Ringer solution intravenously (10% body weight in approximately 50 min), the neck vein pressure increased to 17.3 +/- 0.9 cmH2O and the lymphatic pressure increased to 24.6 +/- 3.8 cmH2O (both P < 0.05). In two additional sheep, the thoracic duct lymph flow rate increased from 0.8 +/- 0.4 ml/min at baseline to 5.5 +/- 2.0 ml/min during the infusions. Our results show that postnodal intestinal lymphatic pressure may increase substantially during intravenous fluid infusions. This is important because increases in postnodal lymphatic pressure may slow lymph flow from the intestine.

Long-term vascular volume expansion maintains elevated thoracic duct lymph flow

OBJECTIVE

To investigate the mechanisms responsible for edema seen during pregnancy, we tested whether lymph vessels are able to pump high volumes over long periods of time.

STUDY DESIGN

In six chronically catheterized nonpregnant ewes, we examined left thoracic duct lymph flow rate and fluid balance responses to the administration of a balanced isotonic solution at a rate of 1 L/hr for 20 hours. Because estrogen administration decreases lymphatic contractility against outflow pressure, we also administered conjugated estrogens (Premarin) during the last 3 hours of the fluid infusion (experimental time 17 to 20 hours).

RESULTS

After volume loading for 16 hours, the mean +/- SEM lymph flow rate, blood volume, and arterial pressure rose 100% +/- 26%, 20% +/- 2.3%, and 16% +/- 8.1%, respectively. Vascular compliance decreased significantly and, as evidenced by a lack of body weight changes, interstitial fluid volume failed to change (p < 0.05, analysis of variance). The transcapillary oncotic pressure difference increased by 2 mm Hg; venous pressure increased by 5.2 mm Hg. These data suggest that transcapillary forces favored fluid movement into the interstitium. Lymph flow rate remains elevated after blood volume expansion to a level similar to that described during pregnancy in sheep. A transient decrease in urinary output (approximately 20%) occurred with no changes in lymph flow rate, arterial pressure, or blood volume.

CONCLUSION

Lymph flow rate is able to compensate for the increased capillary filtration observed during prolonged blood volume expansion.

Increased venous pressure causes increased thoracic duct pressure in awake sheep

The lymph from most organs drains through the thoracic duct and into veins in the neck. We hypothesized that increases in neck vein pressure (Pnv) are reflected through the thoracic duct to the lung lymphatic-thoracic duct junction. To test this, we cannulated the lung lymphatics in the direction of flow in four sheep. We advanced each cannula until it entered the thoracic duct. Thus the pressure at the tip of the lymphatic cannula (Px) was the pressure at the outflow of the lung lymphatics. We also placed a balloon into the superior vena cava. One to two days later, we measured Px in the awake sheep as we inflated the balloon and increased Pnv in steps to 25-45 cmH2O. We found no significant differences in Px and Pnv. Furthermore, Px closely followed Pnv after each step increase in Pnv. These results support our hypothesis that increases in Pnv cause increases in the outflow pressure to lung lymphatics.

Left thoracic duct lymph flow responses to angiotensin II or atrial natriuretic factor infusion in the ovine fetus

In the ovine fetus it is known that left thoracic duct lymph flow rate relative to body weight is four to five times adult levels, but it is not known whether the circulating hormones modulate fetal lymph flow. To explore this, we intravenously infused either angiotensin II (10 to 400 ng/min, n = 8) or atrial natriuretic factor (500 to 1000 ng/min, n = 8) into chronically catheterized fetal sheep for 30 minutes. Significant increases occurred in fetal arterial (p less than 0.0001) and venous (p = 0.018) pressures during the angiotensin II infusion, and thoracic duct lymph flow rate underwent a dose-dependent increase (r = 0.888, p = 0.0033). With termination of the angiotensin II infusion, fetal vascular pressures rapidly returned to control levels, and lymph flow fell from 18.8% +/- 10.1% (mean +/- SE) above control to 13.7% +/- 7.7% below preinfusion levels (p less than 0.01). During the atrial natriuretic factor infusion, fetal arterial pressure and circulating blood volume decreased significantly (p less than 0.01), whereas thoracic duct lymph flow was unchanged. After termination of the atrial natriuretic factor infusion, fetal arterial pressure returned toward control, blood volume remained reduced, and lymph flow rate underwent a transient rise to 35.6% +/- 15.7% (p less than 0.05) above control levels. These data suggest that angiotensin II and atrial natriuretic factor have significant but opposite effects on fetal thoracic duct lymph flow rate, with angiotensin II stimulating and atrial natriuretic factor suppressing lymph flow.

In vitro effects of a thromboxane A2-analogue U-46619 and noradrenaline on contractions of the human thoracic duct

A piece of a human thoracic duct removed at operation was investigated in organ baths. The duct was cut in 8 ring segments each about 1mm long and isometric tension recorded. The segments were exposed to a potassium rich (124mM) Krebs buffer solution. In only two of the segments were contractions induced (7.2 and 1.0mN, respectively). Noradrenaline and the thromboxane mimetic U-46619 induced tonic and phasic contractions. At a noradrenaline concentration of 10(-5)M the phasic contractions had a frequency of 5 min-1. The highest frequency, 9 min-1, was recorded with 3 x 10(-10)M of U-46619 present in the bath. Noradrenaline had a mean Emax of 50% of the previous K+ (124mM)-induced contraction, and the mean pEC50-value was 6.7. The Emax and pEC50-values of U-46619 were 142% and 9.5, respectively. Postjunctional alpha-adrenoceptors and thromboxane A2-receptors may play a role in the contractility of the human thoracic duct.