Effect of a thromboxane synthetase inhibitor on protamine-induced circulatory changes in sheep

BACKGROUND

Rapid intravenous administration of protamine after procedures requiring cardiopulmonary bypass is occasionally associated with severe pulmonary hypertension, systemic hypotension, cardiac dysfunction, and lung edema. We hypothesized that the mechanism for these hemodynamic changes after protamine administration is the release of thromboxane. We therefore examined the effect of a thromboxane synthetase inhibitor (OKY-046) on these hemodynamic changes in a sheep model.

METHODS

Ten female sheep were prepared with lung lymph fistulas and balloon-tipped pulmonary artery, left atrial, arterial, and venous catheters. After a 5-day recovery period, 2 mg/kg protamine was infused 10 minutes after 200 units/kg heparin, with (n = 5; OKY-046 group) and without (n = 5; heparin/protamine group) OKY-046 (10 mg/kg).

RESULTS

In the heparin/protamine group, pulmonary arterial pressure and lung lymphatic flow were significantly increased soon after administration of protamine, from 19 +/- 1 to 51 +/- 2 mm Hg and 5 +/- 1 to 8 +/- 1 ml/hr, respectively. The circulating leukocyte count was significantly reduced, from 3304 +/- 318 to 903 +/- 898 mm3. Cardiac output was also reduced, from 5.8 +/- 0.3 to 3.4 +/- 0.7 L/min/m2. These changes were completely blocked in the OKY-046 group, except for the neutrophil depletion and the increase in lung lymphatic flow.

CONCLUSIONS

We conclude that thromboxane plays a significant role in protamine-induced hemodynamic deterioration and pulmonary permeability changes.

Comparison of the lipid and apolipoprotein composition of skeletal muscle and peripheral lymph in control dogs and in dogs fed a high fat, high cholesterol, hypothyroid-inducing diet

Most studies of peripheral interstitial fluid lipoprotein composition have been made on interstitial fluid-derived from skin and connective tissue. We developed techniques which allowed simultaneous comparison of lymph (a model of interstitial fluid) from skeletal muscle and skin in control (C) and cholesterol-fed (CF) dogs. Lipoprotein fractions were separated by ultracentrifugation. Skeletal muscle interstitial fluid HDL concentrations were approximately twice those of skin. However, the concentration of VLDL-LDL particles was similar in both interstitial spaces. HDL particles from both microvascular beds showed evidence of extensive remodelling when compared to plasma HDL from the same animal. Relative to apo A-I, skeletal muscle HDL was enriched in free cholesterol and apo E (C and CF dogs) and apo A-IV (CF dogs). Skin-derived HDL was consistently enriched in free cholesterol, apo E and A-IV in both C and CF dogs. These studies indicate that similar remodeling of plasma HDL occurs in widely different tissues which together constitute approximately 70% of the total interstitial space. The relatively high concentration of plasma-derived and remodeled HDL within the interstitial space of skeletal muscle is consistent with that tissue's importance in reverse cholesterol transport.

Granulocyte colony-stimulating factor does not exacerbate endotoxin-induced lung injury in sheep

Because it has been suggested that neutrophils play a role in endotoxin-induced lung injury, we examined the effects of increased peripheral blood-neutrophils induced by recombinant human granulocyte-colony-stimulating factor (rhG-CSF) on the lung dysfunction when induced by endotoxin in awake sheep. We prepared chronically instrumented awake sheep with lung lymph fistulae and catheters for hemodynamic monitoring. We compared alterations of pulmonary hemodynamics, lung lymph balance, circulating leukocytes, plasma and lung lymph concentrations of thromboxane B2 and 6-keto-prostaglandin F1 alpha, and arterial blood gases in sheep that received Escherichia coli endotoxin infusion intravenously (1 microgram/kg) in the following two groups: Group 1 (n = 6) received endotoxin alone, and Group 2 (n = 7) received rhG-CSF (125 micrograms/day) intravenously for 3 days before endotoxin was administered in the same manner as in Group 1. The rhG-CSF remarkably increased circulating neutrophils to 24,600 +/- 2,500/microliters in Group 2 sheep at baseline when compared with the level in Group 1 (5,700 +/- 550 microliters). After endotoxin infusion, we observed significant decreases in circulating neutrophils in both groups. There were no differences between the two groups in the time course of changes in pulmonary hemodynamics, arterial blood gases, or arachidonate products after endotoxemia. However, lung lymph flow and lung lymph protein clearance during the late phase were lower in rhG-CSF-treated sheep than in those that received only endotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Neutrophil elastase inhibitors, SC-37698 and SC-39026, reduce endotoxin-induced lung dysfunction in awake sheep

Neutrophils have been implicated as important cellular mediators of the pulmonary dysfunction observed following endotoxemia in chronically instrumented awake sheep. Several areas of research suggest that neutrophil-derived proteases may be mediators of this dysfunction. We hypothesized that neutrophil elastase inhibitors would attenuate the effects of endotoxemia in sheep. To test this hypothesis, we studied the effects of two putative neutrophil elastase inhibitors, SC-37698 and SC-39026 (Searle, Skokie, IL), on endotoxin-induced lung dysfunction in awake sheep. Sheep were given intravenous neutrophil elastase inhibitor alone (20 mg/kg/h for 6 h), intravenous endotoxin (E. coli endotoxin, 0.5 microgram/kg over 20 min) 1 h after beginning the 6-h infusion of elastase inhibitor, or endotoxin 1 h after beginning a 6-h infusion of elastase inhibitor vehicle. SC-37698 attenuated the increase in lung lymph flow and lung lymph protein clearance, the alterations in lung mechanics, and the fall in white blood count. Qualitatively similar effects were seen with SC-39026. These data suggest the need for further research examining the role of protease-antiprotease interactions and the potential utility of neutrophil elastase inhibitors in acute lung injury like that observed in the adult respiratory distress syndrome (ARDS) in the human.

Effect of intravenous administration of apolipoprotein A-IV on patterns of feeding, drinking and ambulatory activity of rats

To characterize the anorectic effect of apolipoprotein A-IV (apo A-IV), we examined the effect of apo A-IV on the patterns of feeding, drinking and ambulation of rats fed ad libitum. A single dose of 200, 135 or 60 micrograms was infused intravenously through a chronically indwelling right atrial catheter just before the dark period. Apo A-IV suppressed food intake by decreasing meal size, but did not affect the interval between meals, the speed of eating, or the latency to eat the first meal after infusion. The anorectic effect of apo A-IV was dose-dependent and was effective for about 3 h after the infusion. The anorectic effect of apo A-IV is specific because inactivation of apo A-IV abolishes its anorectic effect. The anorectic effect of apo A-IV is not shared by apo A-I. Apo A-IV had no effect on drinking behavior or ambulatory activity. The results seem to indicate that apo A-IV specifically decreases the meal size, which supports our hypothesis that apo A-IV may act as a physiological signal for satiation after the ingestion of a lipid meal.

Gemfibrozil increases apolipoprotein A-I and cholesterol concentrations in human peripheral lymph

Peripheral lymph lipoproteins were studied in four hyperlipidaemic men before and after 6 weeks of treatment with gemfibrozil, a drug which is known to increase the fractional catabolic rate of very low density lipoproteins (VLDL) by raising lipoprotein lipase activity in peripheral tissues. Decreases in plasma triglycerides of 18-60% (mean, 45%) were accompanied by increases in lymph apolipoprotein (apo) A-I concentration of 30-108% (mean, 66%; P < 0.01), and in lymph cholesterol concentration of 35-100% (mean, 59%; P < 0.05). The additional lymph cholesterol was distributed over a broad range of lipoprotein particle sizes. Effects on plasma apo A-I concentration (mean, +7%) and plasma total cholesterol concentration (-7%) were not statistically significant. No changes were observed in four untreated control subjects. These findings are compatible with the hypothesis that lipolysis of VLDL at the blood-endothelium interface increases the transfer of apo A-I from plasma to interstitial fluids, and thereby promotes cholesterol efflux from cells.

Influence of detergent aerosol on lung microvascular permeability

Noncardiogenic edema fluid often contains high levels of plasma proteins, which may inhibit the function of the lung surfactant complex and thus decrease interstitial hydrostatic pressures. We questioned whether, in the awake and standing animal, displacement of the alveolar surface lining would alter the permeability of the thin and sparsely supported pulmonary capillaries. Sheep prepared with lung lymph fistulae were given an aerosolized detergent (Det) to displace the lung surfactant complex. After the sheep were given Det, protein flux was significantly increased (P < 0.05). To validate the suggested permeability increase, pulmonary vein occluders were surgically implanted and experiments repeated with pulmonary arterial pressures elevated 10 mmHg above baseline. After 2 h of elevated pulmonary arterial pressure, lung lymph increased fivefold. At this time, lymph-to-plasma total protein concentration ratios for air and saline-plus-ethanol vehicle were significantly lower (P < 0.01) than baseline ratios (0.26 +/- 0.06 and 0.34 +/- 0.07, respectively). No significant difference could be shown in lymph-to-plasma ratios after the sheep were given Det. We conclude that disruption of the alveolar lining can cause a detectable increase in protein flux due, in part, to an increase in microvascular permeability.

Coronary microvascular fluid flux and permeability: influence of angiotensin II, aldosterone, and acute arterial hypertension

Vascular permeability of the coronary and mesenteric circulation is increased in association with the arterial hypertension that accompanies either endogenous activation of the renin-angiotensin-aldosterone system (RAAS) or exogenous administration of angiotensin II (AII). Whether this occurs as a result of increased intravascular pressure or of elevations in plasma concentrations of AII or aldosterone (ALDO) (or both) is unclear. This acute study of filtration-independent coronary fluid exchange and macromolecular permeability was undertaken to address these issues in open-chest, anesthetized dogs. The influence of arterial hypertension, with or without associated elevations in plasma AII or ALDO (or both), on coronary permeability was examined by monitoring the response in cardiac lymph flow, protein concentration, and capillary and intramural coronary artery structure. Experimental groups received a 90-minute intravenous infusion of either AII (n = 8), methoxamine (MX; n = 7), or ALDO plus MX (n = 5) in equipotent doses that raised arterial pressure to comparable levels. When we compared these animals with normotensive, instrumented controls (n = 5), we found that (1) lymph flow was a function of arterial and microvascular pressures in each group; (2) increased protein permeability, myocardial edema, extravasated red cells, and infused colloidal carbon were found in both ventricles with AII, together with endothelial discontinuities and enhanced abluminal capillary endothelial vesicle formation, when plasma ALDO had risen significantly in response to AII; and (3) macromolecular permeability was no different from that in controls after MX or ALDO plus MX. Based on this short-term study of acute arterial hypertension, we would conclude that acute elevations in microvascular pressure increase fluid flux, whereas increased circulating effector hormones of the RAAS, not plasma ALDO or hypertension alone, alter coronary microvascular structure and permeability to macromolecules Responsible mechanisms remain to be defined.

Intravenous saline infusion in rat increases hyaluronan efflux in intestinal lymph by increasing lymph flow

The output of hyaluronan in mesenteric lymph was studied in anaesthetized rats to allow estimation of the turnover rate. The duodenum/jejunum contained 45 micrograms of this glycosaminoglycan per g wet tissue weight. In fasted rats the concentration of hyaluronan in postnodal lymph averaged 15 micrograms ml-1 and the mean efflux was 2.1 micrograms h-1, corresponding to a daily removal of 10% of the intestinal hyaluronan content. An intravenously injected bolus of 0.9% saline 4 ml 100 g-1 followed by an infusion of the same amount per hour increased the hyaluronan concentration in lymph transiently to 22 micrograms ml-1. During the 8-h i.v. infusion the hyaluronan output remained five times above control due to the high lymph flow. Water and hyaluronan content of the small intestine remained unaltered despite the saline load, the maintained tissue level of hyaluronan suggests an increased rate of synthesis.

Effects of continuous infusion of nitroglycerin on pulmonary hemodynamics, lung lymph balance, and prostanoid products in the response to endotoxin in awake sheep

We examined the effects of continuous intravenous infusion of nitroglycerin (NTG) on lung dysfunction induced by endotoxemia in awake sheep chronically instrumented with lung lymph fistula. We measured the responses of hemodynamics, lung lymph balance, and thromboxane (Tx)B2 and 6-keto-prostaglandin (PG) F1 alpha levels in plasma and lung lymph to endotoxin administration (1 microgram/kg, intravenously [IV], over 30 min) with and without continuous infusion of NTG (1 microgram/kg/min). Continuous infusion of NTG alone (n = 5) over 5 hr did not significantly alter systemic, pulmonary hemodynamics, and/or lung lymph fluid filtration. Infusion of endotoxin alone (n = 7) caused remarkable increases in pulmonary artery pressure (Ppa) and lung lymph flow (Qlym) in the early phase. Continuous infusion of NTG (n = 6) significantly prevented the early increases in Ppa and Qlym after endotoxin. The increased values of TxB2 and 6-keto-PGF1 alpha in both plasma and lung lymph after endotoxemia showed the same increases in groups with and without NTG. These findings suggest that the reduction of pulmonary artery pressure induced by NTG decreased the filtration of fluid into the lungs associated with endotoxemia in sheep, and that the mechanism of vasodilating action of NTG is not due to modifications of constrictive-dilated cyclo-oxygenase products of arachidonate, such as TxA2 and PGI2.

Alcohol, hepatic sinusoidal microcirculation, and chronic liver disease

According to the "intact cell hypothesis," ethanol (EtOH) primarily targets nonparenchymal hepatic sinusoidal and perisinusoidal cells, thereby promoting sinusoidal capillarization, which impairs microcirculatory exchange of nutrients and wastes, promotes tissue fibrosis, and only indirectly damages hepatic parenchyma. To test this hypothesis, sinusoidal ultrastructure and hepatic lymph flow and protein composition were examined in rats up to 16 weeks after intragastric EtOH (36% calories)-high fat infusion (Tsukamoto-French model) (TF). The findings were compared to dietary controls and interpreted in light of restricted transsinusoidal protein movement observed in patients with alcoholic cirrhosis. In vitro, alterations in rat hepatic sinusoidal endothelial cell (RSE) morphology, proliferative index, and transendothelial macromolecular permeability (Evans blue-albumin uptake into microcarrier beads) were determined after acute and more chronic exposure to 0.1%-5 vol% EtOH. TF displayed 75% increased liver size, perisinusoidal collagenosis, and basal lamina deposition, ascitic fluid, and doubling of hepatic lymph liquid and protein flux. In vitro, 1% EtOH retracted RSE cell margins, enhanced transendothelial Evans blue-albumin flux and suppressed proliferative index. Thus, high EtOH concentration, clinically attainable in the portal blood during an alcoholic binge, both in vivo and in vitro, promotes early structural and functional alterations in sinusoidal endothelium, which over time may be responsible for progressive restriction of free intrahepatic exchange of liquid, macromolecules, and migrating immune cells.

Effects of follicle-stimulating hormone on inhibin release by different testicular compartments in the adult ram

The aim of this study was to determine the bidirectional release of immunoreactive inhibin-alpha (irINH-alpha) by different testicular compartments in the adult ram and to assess the effects of FSH on the distribution of inhibin in the testis. Immunoreactive INH-alpha was measured by RIA in fluid samples collected concurrently from the three testicular compartments--the seminiferous tubules, the interstitium, and the vascular system--through catheters inserted surgically into the rete testis, testicular lymphatic duct system, and spermatic veins, respectively. Overall, the concentration of irINH-alpha in rete testis fluid was 25 times the level in testicular lymph and over 500 times the concentration in peripheral blood. The pattern of irINH-alpha concentration in rete testis fluid was inversely related to that in testicular lymph, but i.v. administration of FSH had a decoupling effect on this relationship by depressing inhibin concentration in testicular lymph without affecting inhibin levels in rete testis fluid. Nevertheless, increased flow of testicular lymph more than compensated for the transient fall in irINH-alpha concentration so that, overall, the total output of inhibin via the testicular lymphatic duct system (and the vascular system) increased significantly. No persistent or significant changes were observed in the flow rate of rete testis fluid or concentration of irINH-alpha in the fluid after administration of FSH. The time frame for the response of the testis to FSH is indicative of the involvement of a mediator. Electrophoretic analysis of serially collected testicular lymph samples consistently revealed an FSH-induced release of a series of proteins in the M(r) range of 30,000-32,000.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cromakalim (BRL 34915) on resting and evoked activity in frog semicircular canals

The effects of endolymphatic administration of cromakalim and glibenclamide were tested in isolated semicircular canals of the frog. The actions of the drugs were evaluated by recording: (1) the transepithelial potential between the endolymphatic and the perilymphatic sides of the crista ampullaris; (2) the slow nerve potential from the ampullar nerve; (3) the action potential discharge in afferent ampullar nerve fibres; and (4) the perilympathatic potassium concentration in the fluid bathing the outer surface of the crista ampullaris. The above mentioned parameters were recorded both at rest and during mechanical stimulation of the sensory organ. The results demonstrated that the endolymphatic administration of cromakalim (10(-4) M) produced an increase in both ampullar receptor resting activity and in perilymphatic K+ resting levels. By contrast all the parameters related to the mechanically evoked responses were practically unaffected. Glibenclamide (10(-4) M) proved able to cancel or to prevent cromakalim effects. These data suggest that the membrane of the hair cells is endowed with K+ channels regulated by internal ATP whose activation is mainly involved in the processes sustaining ampullar receptors' resting firing rate.

[The microhemodynamics and lymph flow in the small intestine under the action of histamine against a background of water loading and hyperthermia in dogs]

In anesthetized dogs, an increase of the lymph flow and the transcapillary fluid transfer, under the effect of histamine, was due to elevation of capillary hydrostatic pressure and capillary filtration coefficient in the small intestine. Against the background of water load and hyperthermia, histamine induced less obvious shifts of the microhemodynamic parameters and lymph flow in the small intestine.

Lymph chylomicron composition and size are modified by level of intestinally infused cholesterol and triglyceride source in rats

Mesenteric lymph chylomicrons were characterized following acute continuous intestinal infusion of triglyceride emulsions in rats. Emulsions were prepared using corn, olive or butter oils with graded doses of cholesterol (0, 3, 10, 20, 30, 60, 100 mg/g triglyceride) added to each. Chylomicron cholesterol content varied directly with dose of cholesterol infused, ranging from approximately 1.5% (by weight) with no added cholesterol to 5-10% at 100 mg cholesterol/g triglyceride. Minimum effective dose for increasing chylomicron cholesterol content (about twofold) was 20 mg/g triglyceride regardless of the triglyceride source. Esterified cholesterol accounted for most of the increase in chylomicron total cholesterol with corn oil infusion, whereas increases in the unesterified fraction accounted for 10-30% of the increase in total cholesterol during infusion of olive or butter oils. The effect of infused cholesterol on chylomicron lipid composition was dependent on triglyceride source: no effect on phospholipid:triglyceride ratio with corn and butter oils, but increased phospholipid:triglyceride ratio with olive oil at cholesterol doses greater than 20 mg/g triglyceride. Infusion of butter emulsions produced smaller chylomicrons than those produced during infusion of corn or olive oil emulsions.

The role of cyclooxygenase products in lung injury induced by tumor necrosis factor in sheep

Tumor necrosis factor-alpha (TNF alpha) has been proposed as a mediator of endotoxin-induced lung injury. When given to sheep, TNF alpha mimics endotoxin (LPS) causing hypoxemia, pulmonary hypertension, leukopenia, reduced dynamic compliance (Cdyn), increased resistance to airflow (RL), exudation of lung lymph, and enhanced airway reactivity. TNF alpha also induces rapid release of thromboxane A2 (TxA2), prostaglandin E2 (PGE2), and prostacyclin (PGI2). We hypothesized that the inflammatory effects of TNF alpha are due at least in part to cyclooxygenase products, and therefore cyclooxygenase inhibition would have similar effects on TNF alpha-induced lung injury as has previously been demonstrated for LPS-induced lung damage. Using awake sheep with chronic lung lymph fistulas, we measured Cdyn, RL, and FRC using a whole-body plethysmograph. Pulmonary artery (Ppa), left atrial (PLA), and systemic arterial (Psa) pressures were recorded continuously. Arterial blood gases (for calculating AaPO2), leukocyte counts, and lymph samples (for prostanoid levels) were collected every 30 min. Eleven animals underwent paired random-order experiments receiving ibuprofen (14 mg/kg) 1 h before human recombinant TNF alpha (10 micrograms/kg), or an identical dose of TNF alpha alone. Within 15 min of initiating TNF alpha, Ppa doubled and remained elevated for 4 h. Ibuprofen prevented the early rise in Ppa after TNF alpha. In the group receiving TNF alpha alone, increases in Ppa were accompanied by a 60% decline in leukocyte count and a 50% increase in AaPo2 within 30 min. Ibuprofen prevented increases in AaPo2, but it had no effect on leukopenia or late increases in lymph flow.(ABSTRACT TRUNCATED AT 250 WORDS)

[An improvement in the combined treatment of acute peritonitis]

The object of the research was to study regional lymph circulation in abdominal organs in experimental acute peritonitis and determination of the possibility of including lymphotropic therapy in the complex of measures for the management of patients with acute peritonitis. Regional lymph circulation in the abdominal organs was studied in 45 unbred rats, the effect of various lymphostimulators of regional lymph circulation was studied in 35 rats. Lymphotropic therapy was applied in the complex treatment of 106 patients with acute peritonitis in the clinic. The results of the study showed that lymph circulation in the abdominal organs is markedly disturbed in acute generalized peritonitis, in view of which application of lymph therapy in the complex treatment of patients in the postoperative period is pathogenetically substantiated. Lymph therapy improves microcirculation, promotes early restoration of gastrointestinal activity, reduces the expenditure of antibiotics to one half and one fourth, and shortens the term of inpatient treatment.

Effects of Perilla ketone on the in situ sheep lung

We studied the effects of three different doses (15, 20, and 25 mg/kg) of Perilla ketone (PK) on the blood-perfused in situ sheep lung while obtaining external measurements of lung transvascular protein flux. Lymph flow and lymphatic protein clearance increased significantly after all doses of PK. Severe pulmonary edema was confirmed by high postmortem wet-to-dry lung weight ratios and increased extravascular lung water from multiple indicator-dilution studies. Urea permeability-surface area product and effective diffusivity from multiple indicator-dilution studies also increased after PK infusion. Because we observed no evidence of increased capillary pressure or increased microvascular surface area after PK, we conclude that PK significantly increased pulmonary microvascular permeability. Certain aspects of the in situ PK response appeared to be dose dependent. The lungs responded rather quickly to high doses of PK, but an apparent latency period was noted with low doses of PK. Postmortem wet-to-dry lung weight ratios were always high but did not suggest dose dependence. However, times of postmortem measurements were not the same for all doses of PK. The external scan technique appeared to be sensitive to changes that occurred in the lung after PK. Externally detected albumin interstitial-to-plasma mass (mass I/P) ratios were substantially higher after PK than during control in situ studies. In some experiments, final mass I/P ratios increased above 4 approximately 2.0 h after PK compared with control values of 0.2 and 0.4. A delay time between injection and change in mass I/P slope was also observed, which decreased with increasing dose of PK. PK causes a permeability injury in the in situ sheep lung and provides a useful model for studying the sensitivity of permeability measurement techniques such as the external gamma-ray detection method.

Smoke aldehyde component influences pulmonary edema

The pulmonary edema of smoke inhalation is caused by the toxins of smoke and not the heat. We investigated the potential of smoke consisting of carbon in combination with either acrolein or formaldehyde (both common components of smoke) to cause pulmonary edema in anesthetized sheep. Seven animals received acrolein smoke, seven animals received a low-dose formaldehyde smoke, and five animals received a high-dose formaldehyde smoke. Pulmonary arterial pressure, pulmonary capillary wedge pressure, and cardiac output were not affected by smoke in any group. Peak airway pressure increased after acrolein (14 +/- 1 to 21 +/- 2 mmHg; P less than 0.05) and after low- and high-dose formaldehyde (14 +/- 1 to 21 +/- 1 and 20 +/- 1 mmHg, respectively; both P less than 0.05). The partial pressure of O2 in arterial blood fell sharply after acrolein [219 +/- 29 to 86 +/- 9 (SE) Torr; P less than 0.05] but not after formaldehyde. Only acrolein resulted in a rise in lung lymph flow (6.5 +/- 2.2 to 17.9 +/- 2.6 ml/h; P less than 0.05). Lung lymph-to-plasma protein ratio was unchanged for all three groups, but clearance of lymph protein was increased after acrolein. After acrolein, the blood-free extravascular lung water-to-lung dry weight ratio was elevated (P less than 0.05) compared with both low- and high-dose formaldehyde groups (4.8 +/- 0.4 to 3.3 +/- 0.2 and 3.6 +/- 0.2, respectively). Lymph clearance (ng/h) of thromboxane B2, leukotriene B4, and the sulfidopeptide leukotrienes was elevated after acrolein but not formaldehyde.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of a new calcium channel blocker (TA-3090) on lipoprotein profile and intestinal lipid handling in rodents

Recent interest has focused on findings that drugs used to lower blood pressure may adversely modify plasma lipids and lipoprotein metabolism. This observation may explain why pharmacologic control of hypertension has failed to reduce the incidence of morbidity and mortality from coronary artery disease. The present study aims to evaluate the effect of TA-3090, a new calcium channel blocker, on fasting plasma lipids and lipoproteins, as well as on processes of intestinal fat absorption. Rats were treated by gavage with TA-3090 (10 mg/kg twice daily) for 4 days and compared with controls (n = 6 per group). Plasma cholesterol was increased in the treated group to (mean +/- SE) 74 +/- 2 vs 60 +/- 4 mg/dl (P less than 0.01), due mainly to an increased high density lipoprotein-cholesterol level (50 +/- 2 vs 37 +/- 3 mg/dl, P less than 0.005). Notably plasma triglycerides (TG) and low density lipoprotein-cholesterol were not significantly affected. Another group of TA-3090-treated animals was given an intraduodenal fat meal, and the rise in plasma TG and chylomicrons followed over 4 hr. Postprandial hypertriglyceridemia and chylomicronemia were significantly lower at 2 hr (P less than 0.05) and 3 hr (P less than 0.01) compared with controls. In a separate group of animals, the addition of TA-3090 to a 2% intralipid infusion intraduodenally was associated with significantly reduced TG and chylomicron-TG transport into lymph (P less than 0.05). Furthermore, experiments in rats pretreated with TA-3090 intraperitoneally and then given 2% intralipid intraduodenally were shown to have a significant decrease in mean flow rate (27%), TG transport (31%) and chylomicron-TG output (37%), when compared with controls. In vitro studies using jejunal organ culture to examine the effect of TA-3090 on intracellular lipid synthesis and secretion revealed that the addition of the drug to the medium resulted in significantly decreased TG synthesis and secretion. These data suggest that TA-3090 could be effective in increasing HDL-cholesterol and reducing postprandial chylomicronemia. Our findings support a role for TA-3090 directly on enterocyte absorption and/or intracellular lipid transport, and thus indicate the importance of intracellular calcium on these processes.

[Efficacy of TTFCA in reducing the ratio between lymphatic and plasma protein concentration in lymphatic and postphlebitic edema]

In subjects with lymphatic problems and postphlebitic edema there is a significant difference in the ratio between lymphatic and plasma concentration of protein (CL/CP) in the foot. Two groups of patients were studied (one group with lymphedema and the other with postphlebitic limbs) in order to assess the CL/CP ratio before and after TTCFA treatment (Centellase). The study confirmed the efficacy of treatment in achieving a significant reduction of CL/CP and distal edema.

Increased intestinal protein permeability in a model of lung injury induced by phorbol myristate acetate

Multiple nonpulmonary organ failure is a frequent complication of the adult respiratory distress syndrome (ARDS), and contributes significantly to the high mortality rate associated with this disorder. Although previous studies suggest that systemic organ injury may be an integral component of ARDS, little is known about the specific functional alterations that occur in these target organs. The present study was designed, therefore, to test the hypothesis that endothelial damage, as assessed by microvascular permeability changes, develops in systemic organs in a model of acute lung injury. To test this postulate, the microvascular permeability for total protein was estimated using the steady-state relationship between the lymph (CL) to plasma (Cp) protein concentration ratio (i.e., CL/Cp) and lymph flow in autoperfused cat ileum preparations. Specifically, CL/Cp was measured in five cats, 2 h after acute lung injury was induced by intravenously administered phorbol myristate acetate (PMA), 15 micrograms/kg, and the results were compared with those of seven time-matched control animals. Prior to PMA infusion, the PaO2/FIO2 ratio was 451 +/- 28 in both groups and remained unchanged (486 +/- 26) in the control group. By contrast, the PaO2/FIO2 ratio fell to 275 +/- 95 after PMA infusion (p less than 0.05). In addition, whereas CL/Cp was 0.099 +/- 0.008 in the control animals, it increased to 0.36 +/- 0.06 in the PMA-injured animals (p less than 0.01). In summary, this study demonstrated that in this model of acute lung injury produced by PMA-induced activation of circulating inflammatory cells, both acute lung injury and systemic organ injury (i.e., morphologic and permeability alterations) occurred.

Leukotrienes, thromboxane A2, and prostaglandins during systemic anaphylaxis in sheep

We investigated the roles of eicosanoid mediators in acute systemic anaphylaxis in anesthetized sheep. Sheep were sensitized with dinitrophenylated Ascaris suum extract and were challenged with an intravenous injection of dinitrophenylated bovine serum albumin. During anaphylaxis, cyclooxygenase inhibitors eliminated the elevation of arterial plasma levels of thromboxane B2 and 6-ketoprostaglandin F 1 alpha but markedly elevated the levels of leukotriene E4 in lung lymph without significantly eliminating elevation of plasma levels of histamine. Most of the measured physiological abnormalities accompanying anaphylaxis were aggravated by cyclooxygenase blockade. Enhancement of this anaphylactic mediator response was associated with an accentuated and prolonged increase of airway pressure (P less than 0.05, compared with sensitized, antigen-challenged but otherwise untreated sheep), a more intense hypoxemia (P less than 0.0001), and leukopenia (P less than 0.001), changes that were largely eliminated by pretreating with the sulfidopeptide leukotriene (SPLT) antagonist FPL 55712, suggesting that the SPLTs were important mediators of these responses. In contrast, the prolonged, but less severe, systemic vascular collapse and the reduced pulmonary hypertension induced by cyclooxygenase inhibitors were not influenced by the SPLT antagonist. These results demonstrate that in sheep cyclooxygenase metabolites are mainly involved in the acute, but transient, systemic and pulmonary vascular response of systemic anaphylaxis, whereas SPLTs are primarily implicated in the airway and secondary cardiovascular response. SPLT may act either directly or by potentiating the release of and reactivity to histamine and other mediators. Our data therefore suggest that a combination of cyclooxygenase and lipoxygenase inhibition will be necessary to more effectively protect against the consequences of an anaphylactic reaction.