Lymph flow in the thoracic duct of conscious dogs during lymphatic pump treatment, exercise, and expansion of extracellular fluid volume

BACKGROUND: This investigation examined interactions between expansion of the extracellular fluid volume (ECE), osteopathic lymphatic pump treatment (LPT), and exercise on lymph flow in the thoracic duct of eight instrumented, conscious dogs. METHODS AND RESULTS: After recovery from surgery, LPT was performed for 8 min before and after ECE with normal saline, i.v., 4.4+/-0.3% of body weight. Baseline lymph flow was 1.7+/-0.5 mL/min. LPT rapidly increased lymph flow to 5.0+/-1.1 mL/min at 1 min, and lymph flow remained above baseline for 4 min (p<0.05). LPT produced a net increase in lymph flow of 15.4+/-1.1 mL. Following ECE, baseline lymph flow was 4.8+/-0.6 mL/min (p<0.05). LPT increased lymph flow to 9.9+/-1.1 mL/min at 1 min (p<0.05), and lymph flow remained above baseline for 4 min (p<0.05); all flow values after ECE were greater than corresponding values before ECE. However, the net increase in lymph flow produced by 8 min of LPT (18.3+/-3.8 mL) was not significantly greater than that observed before ECE. Moderate treadmill exercise increased lymph flow for 4 min before ECE and for 6 min after ECE. All lymph flows during exercise were greater after ECE than before ECE. The net increase in lymph flow produced by 8 min of exercise was 24.9+/-5.5 mL before ECE and 39.6+/-5.1 mL after ECE (p<0.05). CONCLUSIONS: Expansion of the extracellular fluid volume produced large increases in thoracic duct lymph flow, that were further augmented by lymphatic pump treatment and by moderate treadmill exercise.     

Tissue carbon dioxide tension: a putative specific indicator of ischemia in porcine latissimus dorsi flaps

Free flap surgical procedures are technically challenging, and anastomosis failure may lead to arterial or venous occlusion and flap necrosis. To improve myocutaneous flap survival rates, more reliable methods to detect ischemia are needed. On the basis of theoretical considerations, carbon dioxide tension, reflecting intracellular acidosis, may be suitable indicators of early ischemia. It was hypothesized that tissue carbon dioxide tension increased rapidly when metabolism became anaerobic and would be correlated with acute venoarterial differences in lactate levels, potassium levels, and acid-base parameters. Because metabolic disturbances have been observed to be less pronounced in flaps with venous occlusion, it was hypothesized that tissue carbon dioxide tension and venoarterial differences in lactate and potassium levels and acid-base parameters would increase less during venous occlusion than during arterial occlusion. In 14 pigs, latissimus dorsi myocutaneous flaps were surgically isolated, exposed to acute ischemia for 150 minutes with complete arterial occlusion (seven subjects) or venous occlusion (seven subjects), and reperfused for 30 minutes. After arterial occlusion, pedicle blood flow decreased immediately to less than 10 percent of baseline flow. Blood flow decreased more slowly after venous occlusion but within 3 minutes reached almost the same low levels as observed during arterial occlusion. Venous oxygen saturation decreased from approximately 70 percent to approximately 20 percent, whereas oxygen uptake was almost arrested. Tissue carbon dioxide tension increased to two times baseline values in both groups (p < 0.01). The venoarterial differences in carbon dioxide tension, pH, base excess, glucose levels, lactate levels, and potassium levels increased significantly (p < 0.01). Tissue carbon dioxide tension measured during the occlusion period were closely correlated with venoarterial differences in pH, base excess, glucose levels, lactate levels, and potassium levels (median r2, 0.67 to 0.92). After termination of arterial or venous occlusion, more pronounced hyperemia was observed in the arterial occlusion group than in the venous occlusion group (p < 0.05). Oxygen uptake (p < 0.05) and venoarterial differences in lactate and potassium levels (p < 0.05) were significantly more pronounced in the arterial occlusion group. In the venous occlusion group, with less pronounced hyperemia, venoarterial differences in acid-base parameters remained significantly different from baseline values before occlusion (p < 0.01). The data indicate that tissue carbon dioxide tension can be used to detect anaerobic metabolism, caused by arterial or venous occlusion, in myocutaneous flaps. The correlations between carbon dioxide tension and venoarterial differences in acid-base parameters were excellent. Because carbon dioxide tension can be measured continuously in real time, such measurements are more likely to represent a clinically useful parameter than are venoarterial differences.     

Separation of proteins by high-performance anion-exchange chromatography

The chromatographic separation of four proteins, cytochrome c, alpha 1-acid glycoprotein, ovalbumin, and beta-lactoglobulin, was achieved on a 4.6 X 250-mm wide-pore polyethyleneimine (PEI)-silica gel column (5-micron particles, 330-A pore size) with essentially baseline resolution using a 20-min linear gradient from 0.025 M potassium phosphate, pH 6.80, to 0.50 M potassium phosphate, pH 6.80. The back pressure of this anion-exchange column was 1000 psi at a flow rate of 1.0 ml/min. Protein recoveries averaged over 95% and protein capacity exceeded 33 mg for a single protein. Isocratic elution (0.040 M potassium phosphate, pH 6.8; flow rate, 0.50 ml/min) of ovalbumin gave a column efficiency of 15,700 plates/m with a peak asymmetry factor of 1.27. Resolution of these same four proteins on a 4.6 X 50-mm PEI-silica gel column occurred within 2 min. Nucleoside monophosphates were separated on the short PEI-silica column within 1 min with 0.01 M potassium phosphate, pH 2.58, at a flow rate of 6 ml/min which generated a column back pressure of 2000 psi.     

Intrathoracic sources of caudal mediastinal lymph node efferent lymph in sheep

We investigated the intrathoracic contributions to the caudal mediastinal lymph node (CMN) efferent lymph in 12 anesthetized sheep after removing possible systemic contributions from below the diaphragm. We interrupted various pathways that may send lymph to the CMN (chest wall, esophagus, lung). Because the experiment is destructive, we did the resections in various combinations and waited 1 h between steps. Base-line CMN efferent lymph flow averaged 0.90 +/- 0.52 g/15 min (mean +/- SD). Cutting the pulmonary ligaments bilaterally caused lymph flow to decrease by an average of 58%. In five sheep, cauterizing around the lung hila reduced lymph flow by 16% of base line, cauterizing along the esophagus reduced lymph flow by 18% of base line, and cauterizing along the chest wall increased lymph flow by 6% of base line. After complete isolation of the node, except for the bronchoesophageal artery, dorsal mediastinal vein, and CMN efferent duct, 14% of base-line flow remained. The lymph-to-plasma total protein concentration ratios did not change significantly with any procedure. Under the conditions of our experiments, approximately 74% of base-line intrathoracic CMN efferent flow comes from the lung.     

Electrolyte and other chemical concentrations in tracheal airway surface liquid and mucus

With the ferret in vitro tracheal preparation, we measured the electrolyte and chemical composition of airway surface liquid (ASL) under control conditions and when drugs were added to promote submucosal gland secretion and to change epithelial ion transport. Control ASL was hyperosmolar (342 +/- 2.8 mosmol/kg) compared with ferret plasma and surrounding buffer. Higher values were also found for sodium (167 +/- 1.7 mmol/l), potassium (9.0 +/- 0.05 mmol/l), total calcium (3.46 +/- 0.11 mmol/l), and ionized calcium (2.55 +/- 0.18 mmol/l). pH was lower (7.12 +/- 0.03) than in plasma or buffer. Addition of methacholine to the surrounding buffer increased flow of ASL and potential difference across the mucosa and lowered pH, calcium, sodium, and chloride concentrations. Potassium concentration was increased. Phenylephrine increased flow and decreased calcium concentrations. Salbutamol (albuterol) had no effect on flow but decreased pH and increased calcium and potassium concentrations. Histamine increased flow and calcium concentrations and decreased pH. These changes are presumably due to changes in gland secretion and epithelial transport. Methacholine and phenylephrine increased the sugar content of the secretions, the changes with phenylephrine being larger. Thus resting ASL is hyperosmolar and relatively acid, with high cation contents, and administration of drugs changes its composition by actions on submucosal glands and epithelium.     

The effects of two analogues of arginine-vasopressin (ornithine-vasopressin and desamino-D-arginine-vasopressin) on kidney function in sheep.

The effects of intravenous infusion of ornithine-vasopressin (OVP) and desamino-D-arginine-vasopressin (dDAVP) were studied in normal and hydrated Merino sheep. In normal sheep, OVP resulted in a diuresis, increased urinary sodium and potassium excretion, and a fall in the plasma potassium concentration. Renal plasma flow remained constant but glomerular filtration rate and filtration fraction rose markedly. dDAVP in normal sheep was antidiuretic, but its only significant effect was a small decrease in plasma osmolality. In the hydrated sheep OVP was antidiuretic and resulted in increased urinary excretion of sodium and potassium, and a fall in the plasma potassium level. Renal plasma flow fell, but glomerular filtration and filtration fraction tended to rise. dDAVP in the hydrated sheep was also antidiuretic but urinary sodium and potassium excretion was reduced. Renal plasma flow and glomerular filtration fell, with a small decrease in filtration fraction. These results suggest that the diuretic effect in normal sheep and the electrolyte-excreting effects in both normal and hydrated sheep of OVP are related to the increase in glomerular filtration, which in turn is dependent on the vasopressor activity of the hormone. The increase in glomerular filtration caused by OVP is due to an increase in the filtration fraction of an unchanged renal plasma flow, which could be brought about by an increase in renal efferent arteriolar tone. The effects of hydration of the sheep were the conventional increased urine flow, decreased urine osmolality and decreased solute-free water reabsorption. Sodium and potassium excretion rose slightly and plasma osmolality fell. Renal plasma flow and glomerular filtration both increased with little change in filtration fraction. These effects could be brought about by suppression of endogenous vasopressin and a decrease in both afferent and efferent renal arteriolar tone.     

The Effect of pH and Bicarbonate Ions on the Uptake of Salts by Disks of Red Beet

1. The uptake of potassium chloride by disks of beetroot in solutionsat different pH values has been followed over periods of severaldays.
2. It was found that, as the pH was raised from approximately6to 9 the rate of uptake of potassium from 0.0024 M. potassiumchloride increased, and there was a corresponding increase inthe amount of potassium held by the disks at satura tion. Boththe rate of uptake and the final content of potassium in diskskept in solutions at pH 8.5 were frequently double those atpH 6.
3. The rate of uptake of chloride ions was only slightlyaffectedby the pH value of the medium. The final chloride contentwasapproximately the same in disks kept at different pH values.
4. The above ‘pH effect’ on potassium uptake hasbeenshown to be related to the uptake of bicarbonate ions presentin the alkaline solution; the additional potassium ions accumulatedaccompanying the bicarbonate anions taken up.
5. The bicarbonateions accumulated are converted primarily tomalic acid.

     

Osmotic tolerance and intracellular ion concentrations of bovine sperm are affected by cryopreservation

In this study, the effects of cryopreservation on osmoregulation and ion homeostasis in bovine sperm were studied. We determined: (1) the osmotic tolerance limits and cell volume response upon exposure to anisotonic conditions, (2) the intracellular pH and potassium concentration, and (3) expression and localization of proteins encoding for potassium and chloride ion channels. A flow cytometric approach was used for simultaneous assessment of cell volume and viability of propidium iodide stained sperm in anisotonic media. Osmotic tolerance was found to be decreased after cryopreservation, especially in the 120 to 60 mOsm/kg osmotic range. The critical osmolality at which half of the sperm population survived increased from 55 to 89 mOsm/kg. The osmotic cell volume response for viable sperm was similar before and after cryopreservation, with an osmotic inactive volume of about 70%. The intracellular pH, determined by recording changes in carboxyfluorescein fluorescence of sperm in media with different pH before and after addition of digitonin, decreased from 6.28 in diluted sperm to 6.16 after cryopreservation. The intracellular potassium concentration, determined using the potassium ionophore nigericin and incubation in media with various potassium concentrations, increased from 154 mM to 183 mM before and after cryopreservation, respectively. The levels of the chloride and potassium ion channel proteins chloride channel 3 protein (CLC-3) and two pore domain potassium channel 2 protein (TASK-2), as detected using Western blot analysis, were not affected by cryopreservation. Immunolocalization studies showed that CLC-3 is present in the acrosome and midpiece as well as in the upper and lower tail. In conclusion, cryopreserved sperm exhibit reduced tolerance to hypotonic stress, a decreased intracellular pH, and increased intracellular potassium level.     

Bronchopulmonary lymphocytes and their B and T subpopulations in control and experimental influenza infected mice]

Immunofluorescent studies showed that, whereas the total number of lymphocytes was still increased on the third and fourth weeks of experimental airborne influenza, the B/T cell ratio remained in the same range as in control animals. This ratio is comparable to results with mouse peripheral lymph nodes.     

Inhibin secretion by the sheep ovary

An in-vitro bioassay for inhibin based on FSH content or release by rat pituitary cells was validated for measuring inhibin activity in ovine plasma and lymph. Dose-dependent increases in inhibin activity were detected in peripheral plasma of 4 ovariectomized ewes 1 min after i.v. injections of ovine follicular fluid, and the half-life of inhibin in plasma for 2 ewes was 45 and 50 min, respectively. Inhibin was detected in ovarian lymph but not in ovarian or jugular venous plasma, even after treatment of ewes with PMSG to induce folliculogenesis. Destruction of visible follicles (greater than 0.5 mm diameter) on the ovaries of 4 PMSG-treated ewes by electrocautery was followed by a rapid and sustained decline in secretion of inhibin in ovarian lymph for up to 4 h. Ovarian lymph flow rates were either unchanged or slightly increased after cautery. Oestrogen concentrations in peripheral venous plasma declined within 15-30 min of cautery, but concentrations remained well above baseline. There was a significant decrease in peripheral progesterone concentrations in these same samples, but not until 2-3 h after cautery. FSH in peripheral plasma was depressed or non-detectable in PMSG-treated ewes and neither FSH nor LH concentrations in peripheral plasma were significantly altered up to 4 h after cautery of ovarian follicles. It is concluded that (a) antral follicles (greater than 0.5 mm) are the source of inhibin present in ovarian lymph, and (b) the ovarian lymphatic system is a route by which inhibin could reach the peripheral circulation, particularly in the luteal phase when ovarian lymph flow rates are high.     

Reversal of depressed miduterine arterial flow during hyperthermia-induced respiratory alkalosis

The influence of ambient and arterial PCO2 on miduterine arterial flow of pregnant sheep acutely exposed to hot environments was investigated. Five mixed-breed ewes between 120 and 130 days of gestation were subjected to hot environments (increasing from thermoneutral 23 to 40 degrees C), and arterial blood pH, PCO2, and PO2 were determined at 5-min intervals. Respiratory rate, heart rate, rectal temperature, blood pressure, and miduterine arterial flow were continuously monitored prior to and during elevation of ambient air temperature. When miduterine arterial flow had decreased to 50% of thermoneutral control levels, ambient air CO2 was increased to 2.5%. Elevated ambient inspired CO2 caused a reversal in arterial pH and PCO2 to near thermoneutral levels. Miduterine arterial flow increased to 77% of the control levels following the elevated ambient PCO2 period. Respiratory rate also decreased when ambient CO2 was increased but remained 136% greater than the thermoneutral control level. All other parameters remained near their heat stress (40 degrees C) level during the elevation of ambient CO2. These data indicate that heat-stress-induced depression of miduterine arterial flow is vasoactively regulated, and cause-effect related to both arterial pH and PCO2, and thermoregulatory shunting of blood to heat-dissipating surfaces.     

Contribution of exercising legs to the slow component of oxygen uptake kinetics in humans.

Rates of performing work that engender a sustained lactic acidosis evidence a slow component of pulmonary O2 uptake (VO2) kinetics. This slow component delays or obviates the attainment of a stable VO2 and elevates VO2 above that predicted from considerations of work rate. The mechanistic basis for this slow component is obscure. Competing hypotheses depend on its origin within either the exercising limbs or the rest of the body. To resolve this question, six healthy males performed light nonfatiguing [approximately 50% maximal O2 uptake (VO2max)] and severe fatiguing cycle ergometry, and simultaneous measurements were made of pulmonary VO2 and leg blood flow by thermodilution. Blood was sampled 1) from the femoral vein for O2 and CO2 pressures and O2 content, lactate, pH, epinephrine, norepinephrine, and potassium concentrations, and temperature and 2) from the radial artery for O2 and CO2 pressures, O2 content, lactate concentration, and pH. Two-leg VO2 was thus calculated as the product of 2 X blood flow and arteriovenous O2 difference. Blood pressure was measured in the radial artery and femoral vein. During light exercise, both pulmonary and leg VO2 remained stable from minute 3 to the end of exercise (26 min). In contrast, during severe exercise [295 +/- 10 (SE) W], pulmonary VO2 increased 19.8 +/- 2.4% (P less than 0.05) from minute 3 to fatigue (occurring on average at 20.8 min). Over the same period, leg VO2 increased by 24.2 +/- 5.2% (P less than 0.05). Increases of leg and pulmonary VO2 were highly correlated (r = 0.911), and augmented leg VO2 could account for 86% of the rise in pulmonary VO2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of Medetomidine on Acid-base Balance and Urine Excretion in Goats

Seven goats were given medetomidine 5 μg/kg as an iv bolus injection. Venous blood samples were taken repeatedly and urine was collected continuously via a catheter up to 7h after the injection. Medetomidine caused deep clinical sedation. Base excess, pH and PCO2 in venous blood rose after medetomidine administration. There were no significant changes in plasma concentrations of sodium, calcium, magnesium, creatinine or osmolality, whereas potassium and bicarbonate concentrations increased, and phosphate and chloride decreased. Medetomidine increased plasma glucose concentration, and in 4 of 7 goats glucose could also be detected in urine. Medetomidine did not influence urine flow rate, free water clearance, bicarbonate and phosphate excretion or pH, but renal chloride, sodium, potassium, calcium, magnesium and creatinine excretion were reduced. The results suggest that the metabolic alkalosis recorded after medetomidine administration is not caused by increased renal acid excretion.     

Hemolysis induced by Prymnesium parvum toxin calorimetric studies

The relationship between binding of the hemolytic toxin (prymnesin) to bovine erythrocytes and the amount of heat liberated was examined as a function of pH using a flow microcalorimeter and ³H-labelled toxin isolated from the euryhaline alga Prymnesium parvum. A high degree of correlation (correlation coefficient = 0.986) was found between the amount of heat generated and the quantity of toxin that was allowed to interact with the erythrocytes. No significant binding of toxin was observed at pH 7 but it increased linearly as the pH was reduced to 5.5. Maximum heat and binding occured at a pH range 4.5–5.5. The same pattern was followed in terms of the amount of heat liberated and the hemolytic activity of the toxin. The differences in the maximum binding and heat production as a function of pH was independent of the average red cell volume which remained constant at pH 5.5 and 6.2 (102.4 and 102.6 μm³, respectively).     

The pH Dependency of Relative Ion Permeabilities in the Crayfish Giant Axon

The dependence of the membrane potential on potassium, chloride, and sodium ions, was determined at the pH's of 6.0, 7.5, and 9.0 for the resting and depolarized crayfish ventral nerve cord giant axon. In normal saline (external potassium = 5.4 mM), the dependence of the membrane potential on the external potassium ions decreased with lowered pH while that for chloride increased. In contrast, in the potassium depolarized axon (external potassium = 25 mM), the dependence of the membrane potential on external potassium was minimum around pH 7.5 and increased in either more acidic or basic pH. In addition, the dependence of the membrane potential on external chloride in the depolarized axon was maximum at pH 7.5 and decreased in either more acidic or basic pH. The sodium dependency of the membrane potential was small and relatively unaffected by pH or depolarization. The data are interpreted as indicating a reversible surface membrane protein-phospholipid conformation change which occurs in the transition from the resting to the depolarized axon.     

Effect of pH changes on after potentials of single frog Ranvier nodes

In experiments on single nodes of Ranvier of isolated frog nerve fibers a decrease in pH of the medium to 5 caused a small increase in after-depolarization but an increase in pH to 9 caused virtually no change in it. The after-hyperpolarization arising in potassium-free Ringer's solution was abolished by a decrease in pH but remained substantially unchanged as a result of an increase in pH; posttetanic hyperpolarization was reduced in amplitude and slightly increased in duration by a decrease in pH, but not appreciably changed by an increase in pH. It is concluded that the character of changes in after-potentials of single nodes of Ranvier of isolated nerve fibers in medium of different pH is entirely determined by the influence of this factor on the kinetics of the potassium permeability of the excitable membrane.I. N. Ul'yanov Pedagogic Institute, Ul'yanovsk. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 62–66, January–February, 1976.     

Potentiation of lung vascular response to endotoxin by superoxide dismutase

We studied the effects of superoxide dismutase (SOD), an enzyme that converts superoxide into peroxide, on the cardiopulmonary response to endotoxin in sheep. Sheep (n = 18) were prepared for chronic measurement of cardiopulmonary variables, including lung lymph flow, by surgically implanting catheters under halothane anesthesia. Nine of the animals were studied before and after the administration of endotoxin (0.75 microgram/kg) with and without SOD. An additional nine animals received SOD without the lipopolysaccharide. Endotoxin produced an increase in lung lymph flow that was initially associated with a marked pulmonary arterial (PA) hypertension and reduced lymph-to-plasma protein ratio (L/P). The lymph flow remained elevated later in the response, but there was only a mild increase in PA pressure, and the L/P was normal. There was also a fall in blood neutrophils and in cardiac index. SOD increased this secondary elevation in lung lymph flow, and the corresponding L/P was greater than the preendotoxin value. The fall in neutrophil count, cardiac output, and the elevation in PA pressure seen with endotoxin were not affected by SOD. When administered in the absence of endotoxin, SOD produced no perceptible change in the cardiopulmonary and lymph values. We conclude that peroxide, hydroxyl ion, and/or other free radicals formed by the action of SOD must be responsible for a portion of the endotoxin response rather than superoxide itself.     

Response of the regional lymphatic system of the sheep to acute stress and adrenaline.

An acute pain stimulus resulted in elevated lymph flow and output of cells from the popliteal lymph node of the sheep in the first 15 min after the stress. Efferent lymph flow increased by an average of 93% above the mean resting flow and cell output rose by an average of 170% during this period, but by 30 min after the stress, values for both lymph flow and cell output had returned to normal. The cell content of the efferent lymph was significantly higher in the first 15 min after the acute stress and it is suggested that there is a sizeable pool of lymphocytes within the resting popliteal node which can be mobilized into the lymph by an acute stress. A single intravenous injection of 1 mg adrenaline the efferent lymph flow in all the sheep examined but gave rise to an increased cell output in only 50% of the sheep. This indicated that there may be other factors, possibly hormonal, involved in the movement of the pool of lymphocytes out of the regional lymph node following acute stress. Both acute pain stress and adrenaline resulted in an increased afferent popliteal lymph flow and output of cells from the regional tissues in the first 15 min after administration. The results are suggestive of a small pool of lymphocytes in the regional tissues which may be readily mobilized by either acute stress or adrenaline. Part of the increases in efferent and afferent lymph flow observed following acute stress and adrenaline appeared to be due to an increased lymph formation, presumably as a result of an increased capillary pressure. Nevertheless, it is considered that the greater part of the increased flow of lymph from both regions resulted from an accelerated movement of performed lymph.     

Acute systemic hypoxia elevates venous but not interstitial potassium of dog skeletal muscle

Potassium release through ATP-sensitive potassium (K(ATP)) channels contributes to hypoxic vasodilation in the skeletal muscle vascular bed: It is uncertain whether K(ATP) channels on muscle cells contribute to the process. Potassium from muscle cells must cross the interstitial space to reach the vascular tissues, whereas that from vascular endothelium would have a higher concentration in venous blood than in interstitial fluid. We determined the effect of systemic hypoxia on arterial, venous, and interstitial potassium in the constant-flow-perfused gracilis muscles of anesthetized dogs. Hypoxia reduced arterial Po(2) from 138 to 25 and Pco(2) from 28 to 26 mmHg. Arterial pH and potassium were well correlated (r(2) = 0.9): Both increased in early hypoxia and decreased during the postcontrol. In denervated muscles, perfusion pressure decreased from 95 to 76 mmHg by the end of the hypoxic period; neither venous nor interstitial potassium was elevated. In innervated muscles, perfusion pressure increased from 110 to 172 mmHg by the 11th min of hypoxia and then decreased to 146 mmHg by the end of the hypoxic period; venous potassium increased from 5.0 to 5.3 mM, but interstitial potassium remained unchanged. Glibenclamide abolished both the increase in venous potassium and the hypoxic vasodilation in the innervated muscle. Thus skeletal muscle cells were unlikely to have contributed to the release of potassium, which was suggested to originate from vascular endothelium. The sympathetic nerve supply may play a direct or indirect role in the opening of K(ATP) channels under hypoxic conditions.     

Changes in thoracic and right duct lymph flow and enzyme content during skeletal muscle stimulation.

In the pentobarbital-anaesthetized dog the effect of electrical stimulation of hindlimb skeletal muscles on thoracic and right duct lymph flow and enzyme content was examined. Increase in plasma creatine kinase (CK), L-aspartate-aminotransferase (AST) and lactic dehydrogenase (LDH) during 30-min muscle stimulation were not significantly altered by draining lymph. Both right duct and thoracic duct lymph flow trebled during stimulation. At the same time, the activity of the three enzymes examined decreased in right duct lymph and increased in thoracic duct lymph. Of the latter, only the increase in lymph CK was of a sufficient magnitude to have resulted in a detectable increase in plasma CK. CK was the smallest of the three enzymes studied and apparently preferentially entered the lymph, suggesting that the larger AST and LDH molecules were not likely to have entered the blood plasma directly from skeletal muscle. Rather their entry from some other tissue, possibly the formed elements of the blood, is indicated.