Intracellular calcium stores modulation in lymph vessels depends on wall stretch.

We studied the effect of intracellular calcium stores modulation on the ability of lymph vessels to propel fluid in a preparation of actively contracting isolated bovine mesenteric lymph vessels. Vessels were cannulated at each end, placed in a temperature-controlled organ bath, and circulated with oxygenated Krebs solution. Vessel wall tension (transmural pressure) was changed by raising the height of the fluid-filled reservoir and outflow catheters appropriately. When transmural pressure was set and maintained at 6 cmH2O (1 cmH2O = 98.1 Pa), caffeine (10(-3) M), ryanodine (10(-7) M), and cyclopiazonic acid (CPA; 7 x 10(-6) M) inhibited lymphatic pumping. We also studied the effect of these agents on the relationship between lymph pump activity and transmural pressure, a relationship normally described by a bell-shaped curve. When transmural pressure was increased at 5-min intervals, the magnitude of inhibition by caffeine (10(-3) M) and CPA (7 x 10(-6) M) was greater than when transmural pressure was held constant. Ryanodine, on the other hand, had no effect on lymphatic contractility when transmural pressure was manipulated. The ryanodine results suggest the existence of an interaction between vessel wall stretch and intracellular calcium stores modulation that is not seen with caffeine or CPA.

Elevation of whole-blood glutathione in peritoneal dialysis patients by L-2-oxothiazolidine-4-carboxylate, a cysteine prodrug (Procysteine).

Glutathione is a major cellular antioxidant that protects protein thiols and inhibits cellular damage due to oxygen free radicals. It has been reported previously that patients undergoing dialysis have low levels of blood glutathione, which may lead to increased susceptibility to oxidant stress. L-2-oxothiazolidine-4-carboxylic acid (OTZ) is a cysteine prodrug that raises cellular glutathione levels by increasing delivery of cysteine, the rate-limiting substrate for glutathione synthesis. This study investigates the effect of OTZ on blood glutathione in a blinded, placebo-controlled study of patients with chronic renal failure treated by peritoneal dialysis. Twenty patients were randomly selected to receive OTZ (0.5 g three times a day orally with meals) or placebo for 14 d. Patients visited the clinic for predose blood collection and safety evaluation at baseline (days 3, 7, and 14 and again at 14 d from the last dose [follow-up]). Glutathione concentrations were determined in whole blood by HPLC. OTZ resulted in a significant rise in whole-blood glutathione at days 7 (594 +/- 129 mumol/L) and 14 (620 +/- 108 mumol/L) compared with baseline (544 +/- 139 mumol/L) (P < 0.01 and P < 0.05, respectively). Glutathione was also significantly increased at days 7 and 14 when normalized by hematocrit (Hct) or hemoglobin to correct for anemic status (e.g., 20.7 +/- 5.7 mumol/L per % Hct [day 7] and 20.9 +/- 4.0 mumol/L per % Hct [day 14] versus 18.0 +/- 4.2 mumol/L per % Hct [baseline]; P < 0.05). Glutathione levels did not change in the placebo group at any patient visit, and levels in the OTZ-treated group returned to baseline at follow-up. There were no serious adverse events attributable to OTZ, and the drug appeared to be well tolerated by patients with renal failure treated by continuous ambulatory peritoneal dialysis. Our results show that OTZ increases blood glutathione levels, which may improve antioxidant status in dialysis patients.

Role of protein kinase C in the regulation of pumping activity in bovine mesenteric lymphatic vessels.

We investigated the role of protein kinase C (PKC) in regulating the lymphatic myogenic response. Bovine mesenteric lymphatics were suspended in an organ bath with inflow and outflow ends cannulated. Input was provided from a reservoir filled with Krebs solution. The PKC activator phorbol 12-myristate 13-acetate (PMA) inhibited pumping significantly whether tested at a fixed pressure or as pressures were raised in 2 cm H2O increments (50% inhibition achieved at 4.6 x 10(-8)M. The inactive phorbol ester (4-alpha-PMA) had no effect. The specific PKC inhibitors calphostin (10(-9) to 10(-7)M) or chelerythrine (10(-8) to 10(-6)M) had no significant effect on pumping. However, chelerythrine (10(-6)M) was capable of reversing the inhibitory effects of PMA (5 x 10(-8)M). PKC activation is believed to inhibit nitric oxide (NO) production in some blood vessels, and previous work from our laboratory has demonstrated that NO is important in facilitating pumping activity in bovine lymphatics. We observed that sodium nitroprusside (sNP, 10(-7)M) or L-arginine (10(-4)M), reversed the depressor effects of PMA. These results suggest that PKC may not be involved in regulating the vessel's contractile response to pressure-induced stretch. However, the data with PMA suggest that these ducts contain PKC. PKC activation depresses lymphatic pumping and this effect may be mediated in part, by inhibition of NO.

In vitro simulation of the effect of peritoneal dialysis solution on mesothelial cells.

All previous in vitro biocompatibility tests of peritoneal dialysis fluids have shown that these have inhibitory effects on the function of peritoneal mesothelium. This report presents results from in vitro experiments performed to study the effect of dialysis fluids (Dianeal 1.36 and Dianeal 3.86; Baxter, Round Lake, IL) on the function of mesothelial cells under conditions that simulate the in vivo state of these solutions in the peritoneal cavity. Thus, cells were initially exposed only to the unused fluids that were thereafter gradually diluted (over 4 hours) with pooled effluent dialysate from continuous ambulatory peritoneal dialysis patients. During the following 20 hours, cells were incubated in a mixture of unused fluid (10% vol/vol) and dialysate effluent (90% vol/vol). The mesothelial cells exposed to dialysis fluids under such conditions became activated cells compared with exposed to dialysate effluent (control) alone. Thus, synthesis by mesothelial cells of all tested substances was enhanced during exposure of the mesothelium to the dialysis fluids: interleukin-6: Dianeal 1.36, +257%; Dianeal 3.86, +181% (both P < 0.05); hyaluronic acid: Dianeal 1.36, +72%; Dianeal 3.86, +63% (both P < 0.05); tissue plasminogen activator: Dianeal 3.86, +33% (P < 0.05); and plasminogen activator/inhibitor-1: Dianeal 1.36, +28%; Dianeal 3.86, +38% (both P < 0.05). Our results show that the peritoneal mesothelium becomes activated when it is exposed to acidic, hyperosmotic dialysis fluids diluted with the dialysate effluent, in a manner that imitates the in vivo changes in these solutions during their intraperitoneal dwell.

Intracellular glutathione in human peritoneal mesothelial cells exposed in vitro to dialysis fluid.

Effect of peritoneal dialysis fluids on glutathione (GSH/GSSG) level in human peritoneal mesothelial cells was tested in in vitro experiments. To mimic in vivo conditions, cells were initially exposed to dialysis fluids (Dianeal 1.36%, Dianeal 2.27%, Dianeal 3.86%) that subsequently were diluted with dialysate effluent at time intervals. GSH/GSSG concentration in cells initially decreased but returned to normal values thereafter. This decrease in the intracellular concentration of glutathione was less when pH of the tested dialysis fluid was adjusted to 7.3. In further experiments with mesothelial cells exposed to Earle's salts solution supplemented with glucose and/or lactate, we have shown that in the presence of low pH, lactate is the main factor causing depletion of intracellular glutathione. When added to the dialysis solution at a concentration of 0.1 mM, L-2-oxothiazolidine-4-carboxylate, a precursor of glutathione, not only prevents the initial decrease in glutathione concentration but also augments the final intracellular level of this thiol.

Reduced lymphatic drainage of dialysate from the peritoneal cavity during acute peritonitis in sheep.

OBJECTIVES: The purpose of this study was to investigate the effects of acute peritonitis on lymphatic drainage of the peritoneal cavity in conscious sheep. DESIGN: Peritonitis was induced with the addition of 1% casein or 1% albumin to the dialysis solution. Thirty sheep (5 groups of 6) were used in this study. One group received 50 mL/kg intraperitoneal infusions of Dianeal 4.25% (486 mOsm/L); a second group received 1% casein-Dianeal 4.25% (493 mOsm/L); a third group received 1% albumin-Dianeal 4.25% (487 mOsm/L). In the fourth and fifth groups (controls and casein-injected) lymph was collected from the caudal mediastinal lymph node and the thoracic duct, both of which are involved in the lymphatic drainage of the peritoneal cavity (peritonitis induced with casein). (125)I-human serum albumin (25 mu CI) was added to the dialysate as the lymph flow marker. Lymph drainage was estimated from (1) the appearance of the intraperitoneally administered tracer in the blood; (2) the disappearance of the tracer from the peritoneal cavity; and (3) the recovery of tracer in lymph. RESULTS: In noncannulated animals the cumulative volume removed by lymphatics over 6 hours (based on tracer recovery in blood) was 10.5 +/- 1.0 mL/kg in control animals versus 5.0 +/- 0.6 mL/kg and 8.6 +/- 1.2 mL/kg in casein and albumin-infused sheep, respectively. The suggestion of decreased lymph drainage in peritonitis was supported by the cannulation experiments. While the cumulative fluid removed from the peritoneal cavity over 6 hours in caudal lymph was unaffected by peritonitis (3.8 +/- 0.4 mL/kg in controls vs 3.6 +/- 0.5 mL/kg in casein-injected animals), peritonitis reduced flow into the thoracic duct from 3.0 +/- 0.3 to 1.1 +/- 0.3 mL/kg. The sum of the volume removed in lymph in the cannulated preparations was 6.8 +/- 0.4 mL/kg in controls versus 4.7 +/- 0.5 mL/kg in the peritonitis group. The total volume removed from the cavity (including an estimate of flow based on the residual recovery of tracer in blood) was reduced from 12.6 +/- 1.4 in controls to 7.8 +/- 0.6 mL/kg in the peritonitis sheep. In contrast, estimates of lymph drainage based on the disappearance of tracer from the peritoneal cavity suggested that lymph drainage increased (from 16.6 +/- 1.6 mL/kg in controls to 17.8 +/- 1.5 mL/kg and 25.5 +/- 1.7 mL/kg in the casein and albumin groups, respectively, in noncannulated animals and from 15.3 +/- 1.4 mL/kg in controls to 25.0 +/-1.7 mL/kg in the cannulated group). In both noncannulated and cannulated sheep the total recovery of tracer was less in the peritonitis groups. CONCLUSIONS: These studies demonstrated that lymph drainage of the peritoneal space was decreased in a casein peritonitis model. The decrease in lymph drainage is most obvious in the visceral pathway leading to the thoracic duct; however, diaphragmatic drainage into the right lymph duct may also be inhibited. The disappearance of tracer from the peritoneal cavity was elevated during peritonitis. Tracer disappearance has been used to estimate lymph drainage, but this approach suggested, incorrectly, that lymph flow had increased.

Lymph flow and lymphatic drainage of inflammatory cells from the peritoneal cavity in a casein-peritonitis model in sheep.

The purpose of this study was to characterize the cellular responses in the peritoneal cavity and draining lymph in a sterile peritonitis model in conscious sheep. Lymph was collected from lymphatics that drained the peritoneal space (caudal mediastinal and thoracic ducts) as well as from lymph vessels that drained peripheral tissues (prescapular). Casein was used as the inflammatory agent. Dialysis solution (Dianeal 4.25%) containing 1g% casein and 25 microCi 125I-human serum albumin was infused into the peritoneal cavity in 50 ml/kg volumes. Peritoneal volumes increased from a mean infused volume of 1572 +/- 51 ml to a maximum of 2119 +/- 77 ml at 3 hours. Over 6 hours, the number of macrophages and lymphocytes in the peritoneal cavity remained relatively constant but the number of neutrophils increased from 9.9 +/- 4.2 x 10(7) to 9.2 +/- 1.9 x 10(9) total cells. Caudal lymph which drains directly from the peritoneal cavity through diaphragmatic stomata, demonstrated a 5 fold increase in flow rate over 6 hours following the Dianeal-casein infusion. Thoracic duct and prescapular flows declined approximately 70% and 50% respectively in the same time period. the concentration of lymphocytes and the lymphocyte outputs (product of volume and concentration) declined in all lymph compartments. No elevations in neutrophil numbers in the thoracic and prescapular lymph compartments were observed but neutrophil output in the caudal lymph increased steadily from 3.1 +/- 1.5 x 10(6) to 4.6 +/- 1.3 x 10(7)/hr at the 6 hour mark. We conclude that the major route of removal of inflammatory cells and fluid from the peritoneal cavity is through diaphragmatic lymphatics.

Effect of phosphatidylcholine on lymphatic drainage and fluid loss from the peritoneal cavity of sheep.

The purpose of this investigation was to test the hypothesis that phosphatidylcholine enhances net ultrafiltration by decreasing lymphatic drainage of the peritoneal cavity. Twelve sheep were used in this study. Six animals received 50 ml/kg intraperitoneal infusions of Dianeal 4.25% (490 mOsm/liter) and six received similar volumes of premixed phosphatidylcholine-Dianeal (510 mOsm/liter). Labeled albumin (25 microCi 125I-human serum albumin) was added to the dialysate as a lymph flow marker. Lymph drainage of the peritoneal cavity was estimated from the appearance of the intraperitoneally administered tracer in the blood. Net ultrafiltration was significantly enhanced by phosphatidylcholine at each hour up to 6 hours post-infusion, and over this period reached 30.3 +/- 3.8 ml/kg in the phosphatidylcholine animals compared to 12.2 +/- 2.1 ml/kg in the control group. Phosphatidylcholine treatment decreased the volume removed by lymphatics; by six hours 5.5 +/- 1.1 ml/kg in the animals receiving phosphatidylcholine, and 10.3 +/- 1.0 ml/kg in the control group was drained as lymph. Fluid loss (estimated from the tracer disappearance from the peritoneal cavity) was slightly less in the phosphatidylcholine-treated animals, averaging 15.8 +/- 1.6 in this group versus 16.8 +/- 1.7 ml/kg in the control sheep. However, these differences were not significant. Phosphatidylcholine significantly increased transcapillary ultrafiltration (estimate of volume movement into peritoneal cavity without fluid loss) from 27.6 +/- 1.5 ml/kg in the controls to 43.8 +/- 3.4 ml/kg in the animals receiving phosphatidylcholine.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunological quantification of advanced glycosylation end-products in the serum of patients on hemodialysis or CAPD.

We have developed an immunological procedure for measuring advanced glycosylation end-products (AGEs) in serum. Using this method, we measured AGEs in healthy volunteers, patients with diabetes, renal failure without treatment and in patients with renal failure, treated with hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). We found that AGEs were moderately elevated in diabetics without renal failure and highly elevated in CAPD and HD patients irrespective of their glycemic status. AGE levels correlated significantly with creatinine levels but not with levels of glucose or patient age or sex. AGE levels were reduced significantly post-hemodialysis. Preliminary experiments have shown that circulating AGEs have a molecular weight of approximately 1.5 to 2.0 kDa. More studies are needed to establish if AGE measurements in serum are prognostic indicators of the complications of either diabetes or renal failure.

51Cr-RBCs and 125I-albumin as markers to estimate lymph drainage of the peritoneal cavity in sheep.

The purpose of this study was to compare the use of 125I-labeled human serum albumin (125I-HSA) and autologous 51Cr-labeled red blood cells (51Cr-RBCs) as lymph flow markers to estimate lymph drainage of the peritoneal cavity in conscious sheep. In one group, we assessed lymph drainage from the appearance of intraperitoneally administered tracer in the bloodstream. To determine distribution of drainage into discrete lymph compartments, in a second group of studies, lymph was collected from the caudal mediastinal lymph node and the thoracic duct, both of which are involved in lymphatic drainage of the ovine peritoneal cavity. Ringer lactate solution (50 ml/kg) containing 8-10 microCi each of 125I-HSA and 51Cr-RBCs was infused into the peritoneal cavity. Lymph drainage was calculated by dividing the change in mass of tracer in the blood or lymph compartments by the average intraperitoneal tracer concentration. In noncannulated animals, lymph drainage averaged over 6 h was higher with 125I-HSA as tracer (1.35 +/- 0.12 vs. 0.62 +/- 0.19 ml.h-1.kg-1 with 51Cr-RBCs). A similar pattern was noted in terms of drainage into the caudal lymphatic (0.89 +/- 0.23 and 0.52 +/- 0.19 ml.h-1.kg-1 with 125I-HSA and 51Cr-RBCs, respectively) and thoracic duct (0.16 +/- 0.06 and 0.05 +/- 0.02 ml.h-1.kg-1 with 125I-HSA and 51Cr-RBCs, respectively). Analysis of 125I-HSA and 51Cr-RBC concentrations in lymph and intraperitoneal fluid suggested sieving of RBCs at the diaphragmatic stomata or lymph nodes. Using 125I-HSA as tracer and combining data from noncannulated and cannulated sheep, we estimated peritoneal lymph drainage to be 1.35 ml.h-1.kg-1, with 66% of this flow drained by the caudal vessel, 22% by the parasternal pathway (right lymph duct), and 12% by the thoracic duct.

Lymphatic drainage of hypertonic solution from peritoneal cavity of anesthetized and conscious sheep.

Lymphatic drainage of the peritoneal cavity may reduce ultrafiltration in continuous ambulatory peritoneal dialysis. We assessed lymphatic drainage of the peritoneal cavity in sheep under dialysis conditions by cannulation of the relevant lymphatic vessels and compared lymphatic drainage in anesthetized and conscious animals. Lymph was collected from the caudal mediastinal lymph node and the thoracic duct, both of which are involved in the lymphatic drainage of the ovine peritoneal cavity. Volumes of a hypertonic dialysis solution (50 ml/kg 4.25% Dianeal) containing 25 microCi 125I-human serum albumin were instilled into the peritoneal cavity, and lymph flows and the appearance of labeled protein in the lymphatic and vascular compartments were monitored for 6 h. Intraperitoneal pressures increased 4-5 cmH2O above resting levels after infusion of dialysate. On the basis of the appearance of tracer in the lymph, drainage of peritoneal fluid into the caudal lymphatic was calculated to be 3.09 +/- 0.69 and 14.14 +/- 2.86 ml/h in anesthetized and conscious sheep, respectively. Drainage of peritoneal fluid into the thoracic duct preparations was calculated to be 1.32 +/- 0.33 and 14.69 +/- 5.73 ml/h in anesthetized and conscious sheep, respectively. Significant radioactivity was found in the bloodstream, and at least a portion of this was likely contributed by the right lymph duct, which was not cannulated in our experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intraperitoneal infusion of dextrose and amino acids on the appetite of rabbits.

We studied the effect of intraperitoneal infusion of various volumes and concentrations of dextrose (D) and amino acid (AA) solutions, in a variety of peritoneal dialysis schedules on food intake and biochemical profile in normal and uremic rabbits. Following omentectomy, a peritoneal catheter was implanted. Animals had free access to food, and consumption was measured daily by weight of the remaining food in the cage. We studied the effect of volume (30-50-100 mL/kg), dextrose concentration (0.5-1.5-2.5-4.25-6.6 g/dL) and AA (Travasol based) (2% in Dianeal or glucose-free solution). Dialysis schedules included once/day, twice/day, or four-daily exchanges similar to CAPD. The durations of the exchanges were 4-6 weeks and in certain groups, amino acid exchanges for a week alternated with dextrose exchanges. Our results indicate the following: omentectomy and catheter implantation significantly decrease food intake. There is a significant decrease in food intake after initiation of dialysis that returns to baseline after 2-4 weeks while dialysis continues. Higher volumes (100 mL/kg) decrease food intake significantly, especially with hypertonic solution of either D or AA. There was no difference in food intake between D and AA infusion in any amount of infused volumes. Amino acids do not seem to have a suppressing effect on appetite. However, large volumes and hypertonicity reduce food intake.

An animal model for the study of amino acid metabolism in uremia and during peritoneal dialysis.

We tried to determine the suitability of the rabbit as an animal model to study amino acid (AA) metabolism in continuous ambulatory peritoneal dialysis. We also measured the effect of intraperitoneal (ip) infusion of AA on blood AA changes and food consumption. Plasma AA levels were measured in 10 normal rabbits after an overnight fasting and 30, 60, and 120 minutes after a meal. Following these baseline observations, rabbits were randomly divided into two groups. One group of five rabbits was made uremic after surgical partial nephrectomy, whereas the remaining (controls) underwent sham operations. Two weeks after the induction of uremia we measured the effect of chronic renal failure on fasting and postprandial (30, 60, 120 minutes) plasma AA levels. Upon the completion of the second experiment (4 weeks after the induction of uremia) we studied the effect of an ip AA on plasma AA profile 1, 2, 4, and 6 hours after the infusion in both uremic and control rabbits. We also measured the food intake in all experiments. The results of our experiments showed the following: 1. plasma AA in the rabbits decreased after induction of chronic renal failure and increased after food ingestion and ip infusion of AA solution; 2. neither induction of uremia nor ip AA infusion have an effect on food consumption; 3. the majority of the alterations in plasma AA levels we observed in the uremic rabbits were similar to those observed in humans, indicating that the rabbit may be a suitable model for the study of AA metabolism in chronic renal failure and during peritoneal dialysis.

Quantitation of lymphatic drainage of the peritoneal cavity in sheep: comparison of direct cannulation techniques with indirect methods to estimate lymph flow.

OBJECTIVE: It has been suggested that lymphatics may contribute to ultrafiltration failure in patients on continuous ambulatory peritoneal dialysis (CAPD) by absorbing dialysate and ultrafiltrate from the peritoneal cavity. In most studies lymphatic drainage has been estimated from the disappearance of an instilled tracer from the peritoneal cavity or estimated from the appearance of an intraperitoneally administered tracer in the bloodstream. However, in sheep it is possible to cannulate several of the relevant lymphatics that drain the peritoneal cavity and assess lymph drainage parameters directly. The purpose of this study was to estimate lymph drainage from the peritoneal cavity in sheep using the disappearance of tracer from the cavity and the appearance of intraperitoneally instilled tracer in the bloodstream and to compare these results with those obtained from our previous studies using cannulation techniques. DESIGN: Experiments were performed in anesthetized and nonanesthetized animals. Volumes of 50 mL/kg of Dianeal 4.25% containing 25 microCi of 125I-albumin were infused into the peritoneal cavity. RESULTS: In anesthetized sheep the calculated peritoneal lymph drainage from monitoring the disappearance of tracer from the peritoneal cavity over 6 hours was 1.873 +/- 0.364 mL/kg/hour. Monitoring the appearance of tracer in the blood gave significantly lower peritoneal lymph flow rates of 1.094 +/- 0.241 mL/kg/hour. Directly measured lymph flow rates from our earlier publication were lower still and ranged from 0.156 +/- 0.028-0.265 +/- 0.049 mL/hour/kg, depending on how we estimated the right lymph duct contribution to peritoneal drainage, since we could not cannulate this vessel. We repeated these experiments in conscious sheep. The value for lymph flow estimated from the disappearance of tracer from the peritoneal cavity was 2.398 +/- 0.617 mL/hour/kg and from the appearance of tracer in the blood, 1.424 +/- 0.113 mL/hour/kg. The lymph flow rates monitored from indwelling lymphatic catheters ranged from 1.021 +/- 0.186-1.523 +/- 0.213 mL/hour/kg (again, depending on our estimates for the right lymph duct). CONCLUSIONS: Lymph flow rates measured from indwelling lymphatic catheters provided the most conservative values for lymphatic drainage of the peritoneal cavity under dialysis conditions. Estimates of lymphatic drainage based on the appearance of tracer in the blood gave values that were on average higher. The method using the disappearance of tracer from the cavity to estimate lymph flows overestimated peritoneal lymph drainage. Fluid was lost from the peritoneal cavity, and the estimated proportion of liquid lost through lymphatic drainage depended on the technique used to measure lymph flow rates.

Toxicity of osmotic solutes on human mesothelial cells in vitro.

We evaluated the effect of the various osmotic solutes on the growth rate of human mesothelial cells (HMC) in an in vitro culture. Glucose inhibited proliferation of HMC in a dose dependent way. At high glucose concentrations (60 mM, 90 mM) the effect was instant but at lower concentration (30 mM) decrease in the mesothelial cell proliferation was significant only after five days of incubation. Reversibility of the glucose effect was inversely proportional to exposure time to this solute. Mannitol and glycerol studied in similar concentrations as glucose decreased proliferation of the mesothelial cells less than glucose, whereas amino acid glycine had a similar effect to glucose. However, all osmotic solutes caused similar injury to mesothelial cells membrane as measured by release of LDH. These results suggest that the toxic effect of the osmotic solutes on proliferation of the mesothelial cells depends not only on the hyperosmolality but also on some metabolic effect(s). In an in vitro culture, HMC may provide a suitable model for the study of the toxic effect of dialysis fluid on peritoneal mesothelium.

Lymphatic removal of dialysate from the peritoneal cavity of anesthetized sheep.

Several investigators have suggested that the lymphatic circulation reduces ultrafiltration in continuous ambulatory peritoneal dialysis (CAPD). The purpose of this study was to assess lymphatic drainage of the peritoneal cavity directly in anesthetized sheep under dialysis conditions. Lymph was collected from the caudal mediastinal lymph node and the thoracic duct, both of which are involved in the lymphatic drainage of the ovine peritoneal cavity, and from the prescapular lymph node, which is not involved in peritoneal lymphatic drainage. Fifty ml/kg volumes of a mildly hypertonic dialysis solution (Dianeal 1.5%) containing 25 microCi 125I-human serum albumin were instilled into the peritoneal cavity, and lymph flows and the appearance of labeled protein in the lymphatic and vascular compartments were monitored for six hours. Following the instillation of dialysis fluid there was a tendency for lymph flow rates from the thoracic duct to increase but these changes were not significant. However, flow rates from the caudal lymphatic demonstrated significant increases, especially in the final three hours of the monitoring period. Only about 8% of the radiolabeled albumin was removed from the peritoneal cavity over six hours (that is, 92% was left in the peritoneal space). Of the albumin removed, approximately 17% of this was drained by abdominal visceral lymphatics into the thoracic duct. About 25% passed through the diaphragm into the caudal mediastinal lymph node and into efferent lymph. Since the efferent lymphatic duct of the caudal mediastinal node empties directly into the thoracic duct, about 42% of all protein removed from the peritoneal cavity of the sheep was ultimately transported to the thoracic duct.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphatic drainage of the peritoneal cavity in sheep.

Lymphatic drainage of the peritoneal cavity has been investigated in anesthetized sheep. Studies involving intraperitoneal administration of a complex of Evans blue dye and bovine serum albumin demonstrated the existence of three anatomically distinct pathways. In the first pathway, dye is removed from the peritoneal cavity by diaphragmatic lymphatics that pass into caudal sternal lymph nodes. Efferent lymphatics from these nodes transport the material to cranial sternal lymph nodes. Efferent cranial sternal lymphatics then convey the material either directly or indirectly, via tracheal lymphatic trunks, to the right lymph duct. In the second pathway, the complex is transported from the peritoneal cavity by diaphragmatic lymphatics that pass into the caudal mediastinal lymph node. Efferent lymphatic ducts from this node transport the material to the thoracic duct. The third pathway appears to involve transport of the dye across the mesothelial lining of the abdominal viscera and removal from the interstitium by afferent visceral lymphatics. Material taken up in this manner is ultimately transported to the thoracic duct by efferent visceral lymphatics. Experiments involving measurements of lymphatic absorption of 125I-labeled human serum albumin from the peritoneal cavity indicated that, over the 6-h period studied, 4.55 +/- 1.20 and 1.43 +/- 0.56% of the injected tracer could be recovered in thoracic duct lymph and caudal mediastinal efferent lymph, respectively, and the sum of these values represented 26% of the recovered radioactivity. On the other hand, 16.95 +/- 6.93% of the injected radioactivity could be found in the blood over the same period.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of mesothelial cells proliferation by endogenous growth factor(s).

We have attempted to determine whether human mesothelial cells (MC) have the power to influence their own proliferation. A serum-free medium was conditioned with the mesothelial monolayer for 24 hours and then applied to proliferating MC. Conditioned medium increased proliferation rate of MC. When the medium was heated at 60 degrees C for 60 minutes, the growth-promoting activity of the conditioned medium decreased by 50%, suggesting that MC produce at least 2 growth factors, 1 heat-labile and the other heat-stable. When MC were exposed continuously to a medium containing 90 mM glucose growth factor, production was decreased by 35%. However, when the cells were exposed to glucose only on alternate days, growth-factor production was similar to that in the control medium. On the other hand, MC exposed continuously for 10 days to 90 mM of glucose exhibited a weaker response to endogenous growth factor, even in a normotonic medium with low glucose concentration. Our results suggest that MC synthesize factor(s), which stimulate their own proliferation, and that high glucose concentrations interfere with this production and the subsequent action of growth factor.

Permeability of different parts of the peritoneal mesothelium to solutes: an in vitro study.

The authors studied the in vitro permeability of different fragments of the rabbit's peritoneum to urea, inulin, horseradish peroxidase, and ferritin. Parietal peritoneum has a lower permeability to middle and large molecules than visceral peritoneum. In addition the local anesthetic, bupivacaine had a different effect on the mesothelial permeability of visceral peritoneum than on that of parietal peritoneum.

Effect of various factors on peritoneal lymphatic flow in rabbits.

Peritoneal lymphatic flow in normal and uremic rabbits was measured by estimation of the disappearance of the radiolabelled 131I-albumin from the peritoneal cavity. The results show that lymph flow rate from the peritoneal cavity is not steady and depends on dialysate volume, its tonicity, and protein content. During peritoneal dialysis, peritoneal lymphatic flow is lower at the beginning of an exchange. Peritoneal lymphatic drainage is higher in uremic rabbits compared to normal controls.