Effects of potential blood substitutes (perfluorochemicals) on rat liver and spleen

Deciphering the Emulsification Process to Create an Albumin-Perfluorocarbon-(o/w) Nanoemulsion with High Shelf Life and Bioresistivity

This work aimed at the development of a stable albumin-perfluorocarbon (o/w) emulsion as an artificial oxygen carrier suitable for clinical application. So far, albumin-perfluorocarbon-(o/w) emulsions have been successfully applied in preclinical trials. Cross-linking a variety of different physical and chemical methods for the characterization of an albumin-perfluorocarbon (PFC)-(o/w) emulsion was necessary to gain a deep understanding of its specific emulsification processes during high-pressure homogenization. High-pressure homogenization is simple but incorporates complex physical reactions, with many factors influencing the formation of PFC droplets and their coating. This work describes and interprets the impact of albumin concentration, homogenization pressure, and repeated microfluidizer passages on PFC-droplet formation; its influence on storage stability; and the overcoming of obstacles in preparing stable nanoemulsions. The applied methods comprise dynamic light scattering, static light scattering, cryo- and non-cryo-scanning and transmission electron microscopies, nuclear magnetic resonance spectroscopy, light microscopy, amperometric oxygen measurements, and biochemical methods. The use of this wide range of methods provided a sufficiently comprehensive picture of this polydisperse emulsion. Optimization of PFC-droplet formation by means of temperature and pressure gradients results in an emulsion with improved storage stability (tested up to 5 months) that possibly qualifies for clinical applications. Adaptations in the manufacturing process strikingly changed the physical properties of the emulsion but did not affect its oxygen capacity.

Perfluorocarbon-based oxygen carriers: from physics to physiology

Developing biocompatible, synthetic oxygen carriers is a consistently challenging task that researchers have been pursuing for decades. Perfluorocarbons (PFC) are fascinating compounds with a huge capacity to dissolve gases, where the respiratory gases are of special interest for current investigations. Although largely chemically and biologically inert, pure PFCs are not suitable for injection into the vascular system. Extensive research created stable PFC nano-emulsions that avoid (i) fast clearance from the blood and (ii) long organ retention time, which leads to undesired transient side effects. PFC-based oxygen carriers (PFOCs) show a variety of application fields, which are worthwhile to investigate. To understand the difficulties that challenge researchers in creating formulations for clinical applications, this review provides the physical background of PFCs’ properties and then illuminates the reasons for instabilities of PFC emulsions. By linking the unique properties of PFCs and PFOCs to physiology, it elaborates on the response, processing and dysregulation, which the body experiences through intravascular PFOCs. Thereby the reader will receive a scientific and easily comprehensible overview why PFOCs are precious tools for so many diverse application areas from cancer therapeutics to blood substitutes up to organ preservation and diving disease.

Albumin-derived perfluorocarbon-based artificial oxygen carriers can avoid hypoxic tissue damage in massive hemodilution

Artificial blood for clinical use is not yet available therefore, we previously developed artificial oxygen carriers (capsules) and showed their functionality in vitro and biocompatibility in vivo. Herein, we assessed the functionality of the capsules in vivo in a normovolemic hemodilution rat-model. We stepwise exchanged the blood of male Wistar-rats with medium either in the presence of capsules (treatment) or in their absence (control). We investigated tissue hypoxia thoroughly through online biomonitoring, determination of enzyme activity and pancreatic hormones in plasma, histochemical and immunohistochemical staining of small intestine, heart, liver and spleen as well as in situ hybridization of kidneys. After hemodilution, treated animals show higher arterial blood pressure and have a stable body temperature. Additionally, they show a more stable pH, a higher oxygen partial pressure (pO₂), and a lower carbon dioxide partial pressure (pCO₂). Interestingly, blood-glucose-levels drop severely in treated animals, presumably due to glucose consumption. Creatine kinase values in these animals are increased and isoenzyme analysis indicates the spleen as origin. Moreover, the small intestine of treated animals show reduced hypoxic injury compared to controls and the kidneys have reduced expression of the hypoxia-inducible erythropoietin mRNA. In conclusion, our capsules can prevent hypoxic tissue damage. The results provide a proof of concept for capsules as adequate erythrocyte substitute.

Effect of a Perfluorochemical Emulsion on the Rat Hepatic Mixed Function Oxidase System

The perfluorochemical components of synthetic oxygen transporting emulsions may persist in hepatic tissue. After a single 30% blood exchange with the perfluorochemical emulsion, Fluosol-DA 20%, the effects on the microsomal metabolism of 7-methoxycoumarin and 7-ethoxycoumarin were studied over a 9 week period. Fluosol-DA treated animals were compared with controls (sham) and hetastarch-treated controls. Changes in dealkylase activities were compared with induction by phenobarbitone and 3-methylcholanthrene. The liver to body weight ratio increased by 49% in Fluosol-DA-treated rats over the controls at 1 week and the microsomal protein was increased in the Fluosol-DA-treated rats after 4 and 9 weeks. Fluosol-DA treatment induced 7-methoxycoumarin demethylase with peak differences occurring at 1 week and a Vmax 75% greater than controls. Fluosol-DA was a more potent inducer of demethylase than phenobarbitone. In addition, 7-ethoxycoumarin de-ethylase was induced by Fluosol-DA with a peak induction at 4 weeks. The Vmax at 4 weeks in Fluosol-DA-treated rats was 122% greater than control. In this case, Fluosol-DA produced less induction in de-ethylase than 3-methylcholanthrene. These studies show that Fluosol-DA induces more than one form of cytochrome P450 and the effects resemble those of phenobarbitone more than those of 3-methylcholanthrene. Hetastarch, a plasma expander, did not affect liver weights, microsomal protein content, or the cytochrome P450 system.

Perfluoro-15-crown-5-ether labelled macrophages in adoptive transfer experimental allergic encephalomyelitis

In this serial in vivo study, macrophages labelled with perfluoro-15-crown-5-ether (15C5) were monitored in rats after inducing adoptive transfer experimental allergic encephalomyelitis (AT-EAE). AT-EAE is an animal model of multiple sclerosis and is characterized by inflammatory infiltrates in the central nervous system (CNS) and breakdown of the blood-brain-barrier. A particular feature of AT-EAE are macrophage infiltrates. Purpose of this study was to monitor the invasive and evasive phase of the macrophages in AT-EAE by using 3-dimensional 19F magnetic resonance imaging (3D 19F-MRI). In the early stage of the disease, a much stronger 19F-signal intensity was observed in AT-EAE-rats than in healthy control rats in the tissue adjacent to CNS regions severely affected by inflammatory infiltrates, and thereafter the 19F-signal intensity was decreasing over the time. However, no 19F-signal could be observed in the CNS itself neither in AT-EAE-rats nor in control rats. According to these findings it is assumed that we monitored the evasion of the macrophages from the region of inflammation.

Fluorocarbon emulsions

Perfluorocarbon emulsions have been the topic of intense investigation for many years and presently there are still no absolute indications for their use in clinical practice. The relatively disappointing results of the early clinical studies, as a consequence of using low concentrations of a relatively underdeveloped emulsion, have been responsible for a largely negative impression and it is now essential that the newer second generation emulsions should be judged individually with regard to their efficacy and toxicity under different circumstances. Technological advancement in the fields of chemistry and detergent/emulsifier research will continue and new formulations are being developed which which will require to be tested in models in the laboratory. In the future, this class of drugs will continue to be the topic of intense investigation and their mechanisms of action, which are undoubtedly more complex than the simple carriage of dissolved gases in solution, will be clarified. However, whether fluorocarbon emulsions will ever be used as a 'blood substitute' as was originally anticipated is doubtful.

Several methods utilized for the assessment of biocompatibility of perfluorochemicals

An overview is presented on methods used to judge the effect of different perfluorochemicals (PFCs) on functional organ changes. By some of these methods the function of the reticuloendothelial system (RES) after a load with PFC was tested, either globally in form of the clearance of colloidal carbon particles or by a magnetometric method to test the phagocytosing function of macrophages within the liver of rats. An endotoxin test on survival of mice after the combined treatment with lipopolysaccharides of E. coli and PFCs showed the importance of a cumulative effect of multiple factors influencing phagocytosis. Other methods examined the influence of PFCs on lipid peroxidation during reperfusion of the ischemic intestine or on the effects of hyperbaric oxygen on the lung. The half-life (mean dwell time) of PFCs within organs with a high storage rate could optimally be determined by means of 19F magnetic resonance imaging in longitudinal studies within the same animal. An influence of PFCs on hepatocytes was tested by determining the time required for detoxifying pentobarbital as measured by the sleeping time (until reappearance of the righting reflex). By all these tests a strong dose-dependence was found, so that effects observed with a high load may become negligible with smaller dosages.

Magnetometric measurements of macrophage activity in the liver after administration of different perfluorochemicals

The activity of liver macrophages was evaluated using a magnetometric method after administration of different perfluorochemicals. Following treatment with perfluoroctylbromide a significant shorter time period of diminished macrophage activity was found compared with a mixture of perfluorodecalin and perfluorotripropylamine. Results obtained with the magnetometric method on liver macrophages were more sensitive compared with those of colloidal carbon clearance of total body RES.

Phagocytosis of colloidal carbon after administration of perfluorochemicals of first and second generation

By means of colloidal carbon clearance loading of cells of the reticulo-endothelial system (RES) in rats was estimated after administration of perfluorochemicals. Perfluorocylbromid revealed a significant lower depression of RES function than an equally dosed (g/kg b.wt.) mixture of perfluorodecalin and perfluorotripropylamine. Compared with a magnetometrical measurement of liver macrophage activity, shorter periods of cell loading was determined.

Role of perfluorochemical emulsions in the treatment of myocardial reperfusion injury

Perfluorochemicals are substances with small particle size, low viscosity, and high oxygen-carrying capacity. The role of one perfluorochemical preparation. Fluosol, an emulsion of two perfluorocarbons, a detergent Pluronic F-68 (poloxamer 188), and phospholipids on myocardial reperfusion injury was investigated in a closed-chest canine model of regional ischemia. Intracoronary and intravenous infusions of Fluosol in the perireperfusion period significantly reduced infarct size and improved ventricular function in animals that were examined for up to 2 weeks after reperfusion. Fluosol preserved endothelial structure and endothelium-dependent relaxation of large and small vessels. Fluosol reduced neutrophil plugging of capillaries and attenuated neutrophil infiltration into the reperfused bed. Ex vivo studies of neutrophil function demonstrated apparent suppression of chemotaxis and lysozyme degranulation in cells from animals that were treated with Fluosol. However, treatment of cells in vitro manifested enhanced superoxide anion production within 5 minutes of incubation even with low concentrations of Fluosol. This effect was found to be almost entirely attributable to the detergent, Pluronic F-68. The stimulation of neutrophils by Fluosol was found to result directly from phagocytosis and indirectly from activation of the complement cascade. These findings suggest that perfluorochemicals may provide a novel form of therapy to enhance myocardial salvage after successful reperfusion. The mechanism appears to be due to stimulation and subsequent "deactivation" of neutrophils peripherally, which thereby reduces their cytotoxic potential in the reperfused myocardium. The role of the oxygen-carrying ability of the perfluorocarbons in the reduction of reperfusion injury remains to be determined. In a pilot study in human beings, Fluosol that was used as adjunctive therapy with angioplasty has also been shown to improve regional ventricular function. Clinical trials with perfluorochemical emulsions appear warranted to determine the role of reperfusion injury in limiting myocardial salvage in patients who are undergoing pharmacologic or mechanical reperfusion.

The effect of moderate haemodilution with Fluosol-DA or Hespan on the nonmicrosomal acetylation of sulphadimidine in the rat

The effects of Fluosol-DA (Fluosol) and Hespan haemodilution on the nonmicrosomal acetylation of sulphadimidine were studied in male rats. Fluosol increased the acetylsulphadimidine percent excreted in urine, the metabolic formation rate constant (kf), and the formation clearance (CLF) for 72 h after haemodilution without any significant changes in the sulphadimidine apparent volume of distribution (Vd) or total body clearance (CL). Hespan haemodilution increased the acetylsulphadimidine percent excreted in urine only at 48 h while significantly decreasing the sulphadimidine clearance, urinary excretion rate constant (ku), and renal clearance (CLR) for 72 h. The enhanced N-acetyltransferase activity after Fluosol haemodilution may have therapeutic consequences for concomitantly given drugs metabolized by this enzyme.

Acute effects of moderate Fluosol-DA hemodilution on hepatic microsomal and nonmicrosomal metabolism in rats

Fluosol has been shown to alter the disposition of several drugs immediately after its administration. Investigations in this laboratory established that the disposition of several drug markers requiring the hepatic microsomal cytochrome P-450 isoenzymes was time dependent for 72 hours. It was an additional purpose of the research to determine if the nonmicrosomal sulfation and acetylation pathways were also influenced by Fluosol hemodilution in a time dependent manner. Rats were moderately hemodiluted with Fluosol and received an intravenous dose of a drug marker 24, 48, or 72 hours after hemodilution. The formation clearance (ClF) of specific metabolites was used as the pharmacokinetic measure of a specific enzymatic activity. 3-Hydroxymethyl antipyrine ClF (phenobarbital inducible microsomal cytochrome P-450 isoenzymes) increased 300% only at 48 hours. Acetylsulfamethazine ClF (nonmicrosomal acetylation) increased 287% and 162% at 24 and 48 hours, respectively. Acetaminophen sulfate ClF (nonmicrosomal sulfation) decreased 30% only at 48 hours. Substantial evidence shows that cytochrome P-450 content is induced at 72 hours and remains induced for an unprecedented length of time by the PFCs in Fluosol. Therefore, it was unexpected that 3-hydroxymethyl antipyrine ClF was not increased at 72 hours. Several possible explanations are discussed for the unexpected findings.

Retention of perfluorochemicals in rat liver and spleen

The uptake and retention of perfluorochemicals (PFCs) into rat liver and spleen have been measured for up to 28 d following injection of either the commercial PFC emulsion, Fluosol, or a novel perfluorodecalin (FDC)-based emulsion. Both quantitative and qualitative differences in the retention of individual PFCs were observed, depending on composition of emulsion administered. Nevertheless, uptake of PFCs into the spleen was consistently greater than into the liver, irrespective of formulation injected.

Pharmacologic perturbation of neutrophils by Fluosol results in a sustained reduction in infarct size in the canine model of reperfusion

Previous studies have demonstrated that intravenous administration of large doses of Fluosol, a perfluorochemical preparation, reduced infarct size 24 h after reperfusion, an effect that was associated with reduced neutrophil infiltration. The effect of a clinically tolerable dose of Fluosol on infarct size after a prolonged period of reperfusion and its mechanism of action on neutrophils remain unknown. Twenty-one anesthesized closed chest dogs were subjected to 90 min of proximal left anterior descending coronary artery occlusion and 72 h of reperfusion. An additional five dogs that did not undergo regional myocardial ischemia were utilized to explore the mechanism of action of Fluosol on neutrophil function. In the infarct study, animals were randomized to receive either intravenous Fluosol (n = 10) or an equivalent volume of Ringer's lactate solution (control; n = 11) at 15 ml/kg body weight during the last 30 min of occlusion and for the 1st 30 min of reperfusion. Fluosol significantly reduced infarct size when expressed as percent area at risk 72 h after reperfusion (13.7 +/- 2.7% vs. 38.3 +/- 4.5%, respectively, p less than 0.001). This reduction was associated with significant improvement in regional wall motion (18.4 +/- 2.3% vs. 5.5 +/- 2%, p less than 0.001). Endocardial blood flow in the ischemic bed was significantly higher 3 h after reperfusion in Fluosol-treated dogs (0.63 +/- 0.08 vs. 0.34 +/- 0.07 ml/min per g, p = 0.01). Reduced capillary plugging by neutrophils with relative preservation of endothelial cell structure was observed in Fluosol-treated animals. Infusion of Fluosol produced a marked transient decrease in peripheral neutrophil and platelet counts in both ischemic and nonischemic dogs and was associated with a significant reduction in total hemolytic complement levels. Studies of neutrophil function ex vivo revealed a reduction in chemotaxis and lysozyme degranulation after infusion of Fluosol. In vitro experiments showed that Fluosol produced a rapid and sustained activation of neutrophils determined by superoxide anion production. These data demonstrate that low dose intravenous Fluosol produces a sustained reduction in infarct size in the canine model. The beneficial effect may be in part due to the suppression of various neutrophil functions in the reperfused myocardium subsequent to peripheral activation by Fluosol. Such interventions may offer a novel therapy to enhance myocardial salvage by sequestration of circulating neutrophils during the critical early reperfusion period.

Some aspects of perfluorochemical emulsion's interaction with blood

FDC/FTPA (7:3) emulsions stabilized by procsanol (Emulsion 1) and by procsanol with yolk phospholipids (Emulsion 2) were incubated with the donor plasma. After the incubation during 6 hours of Emulsions 1 and 2 with plasma the 36% and 50% decrease of the cholesterol content in plasma was found. Analysis of the lipid content of lipoproteins after the Emulsion 2 administration to rats (2.5 ml/100 g of weight) revealed the 50% decrease of the cholesterol amount in the HDL fraction at 3 and 24 hours posttransfusion. The ratio cholesterol/total phospholipids in the erythrocyte membrane diminished up to 50% as well. The equal degree of the cholesterol adsorption by emulsion from plasma, HDL of rats and erythrocyte membrane is an evidence of nonspecific interaction of PFC particles with the blood components containing cholesterol.

Magnetometric studies on the reticulo-endothelial system of the liver after administration of different lipid emulsions

A comparison of the burdening effects on the reticulo-endothelial system (RES) by soybean oil emulsions with two different emulsifiers [soybean lecithin (SOB) and egg lecithin (EGG)] or by a perfluorochemical emulsion (Fluosol-DAR, PFC) was performed using a magnetometric method. This method is based on measuring the relaxation of injected iron oxide (gamma-Fe2O3) above the liver after magnetization in a strong external magnetic field. Three different methods of evaluation of the data were chosen. First, according to the conventional monoexponential function, second, according to a monoexponential function with a constant, and third, using the ratio of the initial dynamic to total magnetic field strength. In contrast to SOB and EGG, the PFC emulsion which was used depressed the RES-capacity to less than 31% of the control values (p less than 0.001). Following the administration of SOB the phagosomal motion was significantly lowered after 6 h (p less than 0.01) and 1-2 days (p less than 0.05); thereafter no significant difference of the relaxation constants remained as compared to the control group. The fatty emulsion with egg lecithin showed no significant lowering of the RES-capacity during the entire observation period (p greater than 0.05). Our results indicate that the RES-capacity is diminished not only by a PFC emulsion, but also temporarily by a soybean lecithin emulsion, though not by an egg lecithin emulsion, when given in the same dosages.

Perfluorochemical emulsions decrease Kupffer cell phagocytosis

One drawback to using perfluorochemical emulsions as blood substitutes is that perfluorochemical particles are cleared from the blood by the reticuloendothelial system, primarily liver and spleen. We measured the impact of two perfluorochemical emulsions on clearance of colloidal carbon (less than 1 microns) and 51Cr-sheep red blood cells (about 8 microns) by the reticuloendothelial system in vivo and in the isolated perfused liver. Male rats were injected with 2 ml/100 gm body wt of Fluosol-DA or Oxypherol-ET for 4 consecutive days. Carbon (1 ml/100 gm body wt) or sheep red blood cells (0.05 ml of 5% vol/vol/100 gm body wt) were then injected intravenously (in vivo) or added to perfusate. Samples were taken at several time points for 1 hr. In the isolated perfused liver, carbon clearance was depressed by 25% 1 day after treatment. Rates returned to control levels by 12 days in Fluosol-DA-treated rats but remained depressed by 67% in Oxypherol-ET-treated rats. Sheep red blood cell (8 microns) clearance was two to five times slower than carbon clearance and depressed by 40% in livers from Fluosol-DA rats 1 day and 12 days after treatment. Added serum did not improve phagocytosis. In vivo carbon clearance remained normal in Fluosol-DA-treated rats but decreased by 74% in Oxypherol-ET-treated rats 1 day after treatment, returning to normal by 12 days. Clearance rates were similar in control rats in vivo and in the perfused liver. We conclude that the isolated perfused liver is a good model to measure liver clearance function. Although low doses of perfluorochemical emulsions may depress Kupffer cell phagocytosis, general reticuloendothelial system function is not significantly compromised.

Perfluorochemical erythrocyte substitutes: disposition and effects on drug distribution and elimination

As a result of their ability to transport oxygen, PFC emulsions are being investigated for possible use in a wide variety of conditions. The recent FDA approval of F-DA to diminish myocardial ischemia during angioplasty is the first marketing approval for such a product in the world. The many potential uses of such products may result in their common application in the future, especially as new and better products are developed. The elimination, distribution, and tissue retention of PFC emulsions as well as the physiological changes that occur upon their administration have been the subject of many investigations. The results indicate that these agents may influence the pharmacokinetic properties of other drugs by a wide variety of mechanisms. Several studies have shown significant, but not necessarily consistent, changes in drug elimination and distribution following PFC emulsion infusion. Changes appear dependent on the drug examined, emulsion utilized, degree of blood exchange, species utilized, and the controls chosen for comparison. Often, the changes are time dependent indicating the importance of conducting long-term studies. While PFC emulsions do not appear to alter renal elimination of drugs, several studies have demonstrated that these agents have the potential to induce drug metabolism from several days to possibly months after exposure. Observed changes in drug volumes of distribution, which are often time dependent, may be due to changes in normal drug transport throughout the circulation and/or changes in membrane permeability and cell transport mechanisms. Changes in drug transport may result from depletion of plasma proteins or increases in alpha 1-acid glycoprotein levels due to trauma or PFC emulsion effects. The binding of drugs by PFC emulsion droplets varies greatly and PFC emulsion components displace some plasma protein bound drugs. The wide variability in the results and conclusions of the pharmacokinetic studies conducted to date emphasize the importance of utilizing adequate controls to identify which alterations are PFC emulsion specific.

Dose-dependent reduction of myocardial infarct size with the perfluorochemical Fluosol-DA

The perfluorochemical Fluosol-DA has been shown to reduce infarct size. However, the dose-response relationship of the agent is unknown. Because perfluorochemicals (PFC) can potentially saturate the reticuloendothelial system and decrease carbon clearance as well as cause a transient elevation in liver enzymes, the present study was conducted to determine the lowest effective dose. New Zealand White rabbits (n = 73) were randomly selected prior to infarction to receive 10, 15, 20, 25, or 30 ml/kg PFC or an equivalent volume of 5% dextran (control) intravenously. Animals underwent 30 minutes of coronary artery occlusion with PFC or dextran infused over a 30-minute period starting at 20 minutes into the occlusion. Animals were put to death at 24 hours and infarct size was determined histologically and quantitated by computerized planimetry. Neutrophil infiltration into the ischemic myocardium was evaluated semiquantitatively. No hemodynamic differences were noted within groups. Infarct size was similar to that of controls in animals treated with 10 or 15 ml/kg PFC. Significant infarct size reduction, however, was noted in animals treated with 20, 25, and 30 ml/kg PFC versus controls; (p = 0.05, 0.04, and 0.02, respectively). Maximal infarct size reduction was seen with 30 ml/kg PFC (35%). Neutrophil infiltration was significantly decreased in all groups treated with PFC. These results show that intravenous Fluosol-DA significantly reduces infarct size at a minimal dose of 20 ml/kg.

The effect of varying extents of Fluosol-DA or normal saline haemodilution on the dose dependent kinetics of phenytoin in the rat

Phenytoin kinetics were determined in rats in which the blood was moderately haemodiluted with 20 or 40 mL kg-1 of Fluosol-DA or normal saline. Rats received one of three intravenous phenytoin doses (10, 40, 50 mg kg-1) 0.5, 24, 48, or 72 h after haemodilution and were compared with non-exchanged controls. Haemodilution with either 20 or 40 mL kg-1 of Fluosol or saline had no influence on the dose-dependent kinetics of phenytoin. Haemodilution with 40 mL kg-1 of Fluosol decreased the half-life of phenytoin's major metabolite, HPPH, after a 50 mg kg-1 dose. Neither Fluosol nor saline haemodilution affected the normal delay in biliary cycling of HPPH.

Study of the excretion mechanism of a perfluorochemical emulsion

The excretion mechanism of perfluorochemicals (PFC) via the lung has been studied by physicochemical and histochemical methods. Monocytes that had phagocytized PFC particles were found in the lung capillaries, and alveolar macrophages that had phagocytized PFC particles were found in the alveoli. Vacuolated macrophages were observed microscopically in the alveolar space of rats injected with PFC emulsions. The PFC content in alveolar macrophages reached a maximum level of 1.44 mg/l x 10(8) cells 72 h after injection. It was confirmed by means of a wavelength dispersive x-ray analyzer that fluorine atoms were present in the vacuolated alveolar macrophages. The peroxidase activity of the PFC-phagocytizing macrophages suggest that monocytes phagocytize PFC particles in the circulation and migrate to the alveolar space. This study shows that the monocyte/macrophage system is related to one mechanism for excretion of PFC after intravenous injection of PFC emulsions.

Enhancement of the Arthus reaction and suppression of delayed type hypersensitivity (DTH) by pluronic F-68, a detergent frequently used to prepare perfluorocarbon emulsions

The effect of a 20% w/v RM101 (perfluorobutyltetrahydrofuran) emulsion containing 5% w/v of the detergent Pluronic F-68 or 5% w/v Pluronic F-68 given alone on the Arthus reaction and on delayed type hypersensitivity (DTH) were evaluated in female A/J mice. The test substances were administered i.v. at 1% body weight at 0,4,7,14 and 28 days prior to the i.p. immunization with 10(7) sheep red blood cells (SRBC). The increase in footpad swelling at 4 h (Arthus reaction) and at 24 h (DTH) after elicitation with the s.c. administration of 10(8) SRBC into the left footpad was used to assess immune competence. Pluronic F-68 given alone enhanced the Arthus reaction only when administered on day 0 of immunization. Pluronic F-68 given alone, as well as the perfluorocarbon emulsion containing Pluronic F-68, suppressed the 24 h DTH for as long as 4 days prior to immunization. Nonemulsified perfluorocarbon, on the other hand, had no effect on either the Arthus reaction or on DTH. The immunostimulatory agent, levamisole, administered (10 mg/kg i.p.) 1.5-2 h prior to immunization with SRBC counteracted both the Arthus reaction and the DTH response produced by Pluronic F-68. The present data clearly demonstrate that the changes in Arthus reaction and the DTH response are due to the Pluronic F-68 used to emulsify the RM101 perfluorocarbon; the changes induced by the detergent in these two immune parameters probably involve separate mechanisms.

The effect of moderately severe hemodilution with Fluosol-DA on cytochrome P-450 mediated antipyrine metabolism

Antipyrine metabolism was determined in conscious, unrestrained rats after isovolemic hemodilution with FluosolR-DA. Rats received an intravenous antipyrine dose (20 mg/kg) 0.5, 24, 48, or 72 hours after hemodilution and the pharmacokinetic parameters were compared to non-exchanged control (CONT) animals. Antipyrine clearance (Cl) was significantly decreased at 0.5 and 72 hours after hemodilution. Hemodilution did not significantly alter the antipyrine apparent volume of distribution (Vd) for 48 hours; however, Vd was significantly decreased by 60% at 72 hours. The cytochrome P-450 mediated formation of 3OHME and 4OH was significantly increased at 48 and 72 hours due to an increased metabolite formation rate constant (kf) and not an enhanced metabolic clearance (Clm).

The effect of varying percentages of haemodilution with fluosol-DA or normal saline on antipyrine metabolism in the rat

Antipyrine disposition and metabolism in conscious, unrestrained rats after 25 or 50% haemodilution with Fluosol or normal (0.9% NaCl) saline is reported. Rats received an intravenous antipyrine dose (20 mg kg-1) 0.5, 24, 48, or 72 h after haemodilution and its pharmacokinetic parameters have been compared with non-exchanged control animals. Haemodilution 25% with Fluosol initially depressed antipyrine metabolism for 24 h by decreasing the antipyrine urinary excretion rate constant and the formation rate constants of 4-hydroxyantipyrine (4-OH) and 3-hydroxymethylantipyrine (3-OHME). Metabolism was then increased for 48 and 72 h with a slight increase in all rate constants. Haemodilution 50% with Fluosol produced a similar pattern but with significant increases in the 3-OHME formation rate constant found at 48 and 72 h. Haemodilution 25% with saline reduced 4-OH formation for 48 h. Haemodilution 50% with saline significantly reduced antipyrine urinary excretion at all times. After a significant increase in the 4-OH and 3-OHME formation rate constants at 24 h following 50% haemodilution with saline, the rate constants were significantly decreased at 48 and 72 h. Haemodilution 25% with Flusol significantly reduced the antipyrine Vd at 0.5 and 72 h. After haemodilution 50% with Fluosol, the Vd alternated between values greater and less than control throughout the 72 h. Haemodilution 25 or 50% with saline had little influence on Vd.

Lymphoid tissue responses to emulsified perfluorochemicals: comparative aspects

The effects of a single, low dose (10 ml/kg) injection of the perfluorochemical (PFC) emulsion, Fluosol-DA 20%, on lymphoid tissues and antibody production against sheep red blood cells (SRBC) have been studied relative to the timing of immunization in rats and mice. Intravenous (i.v.) or intraperitoneal (i.p.) injection of emulsion in both species produced alterations in lymphoid tissue weights and the magnitude of these responses was highly tissue- and species-specific. Injection of Fluosol-DA tended to potentiate the humoral immune response to SRBC but this depended on timing and route of emulsion administration relative to immunization. We conclude that lymphoid tissue responses to emulsified PFCs are highly variable and depend upon a number of factors including: emulsion composition and dose; route and timing of administration relative to immunological "challenge"; tissue and species examined.

Lymphoid tissue responses to perfluorocarbon emulsion in rats: time course effects relative to immune challenge

1. The effects of either intraperitoneal (i.p.) or intravenous (i.v.) injection of low doses (10 ml/kg) of the commercial emulsion, Fluosol-DA 20% (F-DA), on lymphoid tissues and antibody production against sheep red blood cells (SRBC) have been studied relative to the timing of immunization in rats. 2. Spleen and liver weights were significantly increased in response to injection of F-DA although no consistent pattern was observed. 3. Thymus weight was decreased following F-DA injection in some experimental groups whereas mesenteric lymph node (MLN) weights were unchanged throughout. 4. The mean plasma antibody titre to SRBC was significantly increased in some groups of animals injected with F-DA both before or after immunization; maximum titres were observed following injection of emulsion simultaneously with SRBC. 5. These results show that lymphoid tissue weights and plasma antibody titres in rats immunized with SRBC vary according to the timing and route of a previous or subsequent injection of F-DA.

Emulsified perfluorochemicals for oxygen-transport to tissues: effects on lymphoid system and immunological competence

Data from both in vivo and in vitro studies to assess lymphoid tissue and immune system responses to emulsified PFCs and their components have been discussed. It may be concluded that the extent to which PFC emulsions are retained in lymphoid tissues and their effects on the manifestation of humoral immune responses to immunological "challenges" is variable and depends upon: (1) Emulsion composition; (2) Dose administered; (3) Route of administration; (4) Tissue examined; (5) Timing of emulsion administration relative to immune challenge; and (6) Species studied. Such variability in the responses to emulsified PFCs has inevitably introduced difficulties in assessing their effects upon immunological competence. Further work is needed determine the extent to which lymphoid tissue functions may be altered by PFC emulsions and identify the active component(s) and mechanism(s) involved.

Lymphoid tissue responses to a novel perfluorochemical emulsion in rats

The effects of a novel perfluorochemical emulsion on rat lymphoid tissues and antibody production against sheep red blood cells (SRBC) have been studied. The responses were compared with those following injection of identical doses of the proprietary emulsion, Fluosol-DA 20% (F-DA). Liver weight was increased up to 15% at 8 days following intravenous (i.v.) or intraperitoneal (i.p.) injection of the novel emulsion but was unaffected by F-DA injection. Spleen weight also increased by a maximum of 20% in response to i.p. injection of the novel emulsion but this was less than increases of up to 44% which occurred in F-DA-injected rats. Thymus weight decreased (P less than 0.05) following i.p. injection of the novel emulsion whereas mesenteric lymph node (MLN) weight remained unchanged. However, MLN weight was increased in response to i.v. injected F-DA, while thymus weight showed a small increase following i.p. F-DA injection. Mean plasma antibody titres to SRBC were significantly (P less than 0.01) increased at 7 days after immunization in rats pretreated with i.p. injections of either the novel emulsion or F-DA; titres in animals pretreated with i.v. injections of either emulsion were similar to control.

Role of fluid replacement, increased oxygen availability by perfluorochemicals and enhanced RES function in the treatment of mesenteric occlusion shock

Experiments were carried out on 183 rats to study the effect of a complex therapy for treatment of mesenteric shock. The superior mesenteric artery (SMA) was temporarily ligated for 90 min under ether anesthesia; this was followed by an analgesic treatment. After release of the ligated artery, fluid therapy was instituted by administering the equivalent of 7.5% of body weight of one of three different solutions: ringer lactate (RL), hydroxyethyl starch (HES) in RL, and perfluorochemicals (PFC, 4 g/kg b.wt. in RL with HES), the latter with the aim to improve the oxygen transport to the tissue. The same fluid therapy was carried out on rats pretreated with E. coli endotoxin. Endotoxin pretreatment was chosen to compensate the negative effect of PFC on the reticuloendothelial system (RES) as shown in previous studies. Survival time and survival rate were recorded as well as hematocrit values at different times before and after treatment. Experimental groups were:

CONTROLS

(1) SMA occlusion without release; (2) 90-min occlusion without therapy. Treated animals: (3) RL therapy; (4) therapy with HES in RL; (5) therapy with PFC in RL and HES; (6), (7), and (8) identical therapies as Groups 3, 4, and 5, respectively, but with endotoxin pretreatment. Survival time increased to the same extent if HES or PFC were added to RL. There was a further increase both in survival times and rates with endotoxin pretreatment (Groups 6, 7, and 8 vs. Groups 3, 4, and 5). The highest survival time and rate were obtained in Group 8, which received PFC therapy with endotoxin pretreatment. There was a slight negative correlation between survival time and hematocrit values if all groups were considered together.(ABSTRACT TRUNCATED AT 250 WORDS)

Half life and changes in the composition of a perfluorochemical emulsion within the vascular system of rats

The decline of the concentration of perfluorochemicals (PFC) after a single injection of three different doses was studied in the circulation of rats. The doses used amounted to 4.4, 10 and 14 g/kg body weight of Fluosol-DA, an emulsion of 7 parts of perfluorodecalin (FDC) and 3 parts of perfluorotripropylamine (FTPA). This also allowed testing of the composition of the emulsion remaining in the circulation and of that found in the liver. After two days a decrease of the half life from 34.0 +/- 0.7 to 17.1 +/- 4.3 h was found within the circulation at the highest dose. At the same time a change in the composition of the emulsion in the blood stream occurred, favouring the fraction of FTPA. FTPA increased from 28.3 +/- 1.4 to 54.4 +/- 8.1% on the fourth day. Whereas in the cells of the liver PFC droplets may be broken up, freed from their surfactant layer and handled according to their individual components, for PFC in the blood stream an unchanged composition should be assumed. Both results, the decreasing half life and the change in composition of the circulating emulsion may best be explained by a shrinking and instability of the emulgator film, showing the necessity for development of a superior surfactant.

Effect of moderate haemodilution with Fluosol-DA or normal saline on indocyanine green and (+)-propranolol kinetics

Indocyanine green (ICG) and (+)-propranolol kinetics were determined in the rat following moderate (50%) blood exchange with either Fluosol-DA or 0.9% NaCl (saline). Rats received an intravenous ICG dose (5 mg kg-1) before an intravenous dose of (+)-propranolol (2.5 mg kg-1) 0.5, 24, 48 or 72 h after haemodilution and were compared with non-exchanged controls. Haemodilution with Fluosol-DA reduced the ICG elimination rate constant during the first 24 h while a significant reduction was seen 48 h after normal saline exchange. ICG clearances tended to be less than the control value, and were significantly reduced only at 24 h after Fluosol-DA exchange due to a reduced Varea. (+)-Propranolol half-life was significantly increased 48 and 72 h after saline exchange; (+)-propranolol clearance was also significantly reduced 72 h after Fluosol-DA exchange. ICG clearance may be reflecting a hypovolaemic change which occurs after haemodilution, which would reduce the hepatic blood flow. However, (+)-propranolol clearance was not altered, suggesting that the hepatic blood flow is not changed. It is possible that ICG clearance is changed due to alterations in its extraction ratio instead of hepatic blood flow changes.

Effect of moderate haemodilution with Fluosol-DA or normal saline on low-dose phenytoin and (+/-)-5-(4-hydroxyphenyl)-5-phenylhydantoin kinetics

Phenytoin kinetics were determined in the rat following moderate (50%) blood exchange with either Fluosol-DA or normal saline. Rats received an intravenous phenytoin dose (10 mg kg-1) 0.5, 24, 48, or 72 h after exchange and were compared with non-exchanged controls. Phenytoin t 1/2 was not altered by exchange with either fluid. Its Cl and Vd were decreased and AUC increased 24, 48, and 72 h after saline exchange and 24 h after Fluosol-DA exchange. (+/-)-5-(4-Hydroxyphenyl)-5-phenylhydantoin (HPPH), a major metabolite of phenytoin, showed a decreased t1/2 and VHPPH 24, 48, and 72 h after exchange with either fluid; t1/2 was also reduced 0.5 h after Fluosol-DA exchange. The decreased Vd and VHPPH may result from changes in cardiac output secondary to haemodilution, or may represent a redistribution in the microcirculation. Fluosol-DA appears to enhance phenytoin and HPPH metabolism 48 and 72 h after exchange.

The effect of Fluosol-DA on the reticuloendothelial system in surgical patients

The effect of Fluosol-DA (Perfluorochemicals), an oxygen carrying blood substitute, on the function of the reticuloendothelial system (RES) was investigated by means of Ferrichondroitin sulfate in a series of patients undergoing gastrectomy for cancer of the stomach. In 20 patients, 500 ml of blood were replaced with the same amount of either Fluosol-DA or hydroxyethylstarch (HES) prior to surgery. Changes of perioperative cellular immunity were studied by PHA-stimulated T-lymphocyte transformation. It was found that the RES functions were significantly depressed postoperatively and fairly recovered by the sixth postoperative day in the Fluosol-DA group. A prolongation of the suppression of cellular immunity with sustained fever was noted in this gastrectomized series. In analyzing the decay of infused Perfluolochemicals in blood, the half life of Fluorodecalin (FDC) was 4.9 +/- 0.1 hr, for Perfluorotripropylamine (FTPA) it was 5.1 +/- 0.1 hr. The prolonged depression of the RES function might be caused by saturation of RES with particles of Perfluorochemicals.

Lymphoid tissue responses to perfluorocarbon emulsion in mice

The effects of either intraperitoneal or intravenous injection of low doses (5 or 10 ml/kg) of the proprietary emulsified perfluorocarbon-based blood substitute, Fluosol-DA 20%, on mouse lymphoid tissue and antibody production against sheep erythrocytes (SRBC) have been investigated. Mean liver weight was significantly increased and gut mesenteric lymph node (MLN) weights decreased in all animals injected with Fluosol-DA, irrespective of route of administration. In contrast, spleen weight decreased following intravenous injection of emulsion at 5 ml/kg. The mean plasma haemagglutination response to SRBC was significantly (P less than 0.01) increased in animals injected intraperitoneally with Fluosol at both doses but was similar to control in all other cases. These results show that lymphoid tissue responses to Fluosol-DA in mice are variable and that antibody production against intraperitoneally-injected SRBC is enhanced by prior injection of emulsion into the peritoneal cavity.

Perfluorocarbons as oxygen-transport fluids

1. An overview of the proposed biological applications of perfluorocarbons and their emulsions as oxygen-transport fluids is presented. 2. Aspects of the properties, preparation, composition and physiological assessment of perfluorocarbon emulsions are discussed. 3. The experimental basis for some of the potential therapeutic uses of PFCs in liquid ventilation, treatment of decompression sickness, organ perfusion, oxygenation of ischaemic and malignant tissues, and as contrast media for NMR imaging is described. 4. The extent to which emulsified perfluorocarbons may have value as substitutes for red blood cells is discussed in detail. Data from both animal and human studies with such emulsions is reviewed. Brief consideration is also given to the possible use of native and modified haemoglobin in blood replacement together with recent work on the preparation of so-called "synthetic red cells".

Changes in plasma enzyme concentrations in response to blood substitution with perfluorocarbon emulsion in the conscious rat

The effects of near total blood replacement with the proprietary perfluorocarbon (PFC)-based emulsion, Fluosol-DA 20%, on plasma concentrations of 2 enzymes, lactate dehydrogeanse (LDH) and alkaline phosphatase (ALP), have been examined in conscious, chronically catheterized rats. A pronounced fall in both plasma LDH (p less than 0.05) an ALP (p less than 0.01) occurred in response to exchange-transfusion. However, at 6 h following blood replacement, plasma concentrations of both enzymes had risen to values significantly greater than those measured immediately before perfusion. The observed changes in plasma LDH and ALP after blood replacement with Fluosol-DA indicated alterations in normal functioning of tissues from which these enzymes originate.

Antipyrine kinetics following partial blood exchange with Fluosol-DA in the rat

The effects of partial blood exchange with Fluosol-DA on hepatic microsomal oxidative metabolism have been studied in the rat. Antipyrine clearance (Cl) was used as an in-vivo measure of the activity of the mixed function oxidase system. Rats were partially exchanged with Fluosol-DA and dosed with antipyrine at selected time intervals following exchange. No change in antipyrine Cl was observed at 0.5 h, but there was a statistically significant decrease at 24 h and then an increase by more than 50% relative to control at 48 and 72 h. These data indicate that the effects of Fluosol-DA on hepatic function are time-dependent and that Fluosol-DA has the potential both to inhibit and to enhance hepatic metabolism. The possibility of altered hepatic metabolism should be considered when patients transfused with Fluosol-DA are given drugs primarily metabolized by the mixed function oxidase system.

Effects of a perfluorocarbon emulsion, Fluosol-DA, on rat lymphoid tissue and immunological competence

The effects of administration of low doses (5 or 10 ml/kg body wt) of the proprietary perfluorocarbon emulsion blood substitute, Fluosol-DA 20%, on rat lymphoid tissue and antibody production against sheep red blood cells (SRBC) have been studied. Spleen and mesenteric lymph nodes (MLN) were significantly heavier at eight days after injection of Fluosol, whereas liver and thymus weights were unchanged. The mean plasma antibody titre to sheep red blood cells was significantly (P less than 0.05) increased in animals injected intraperitoneally with both doses of Fluosol-DA before immunization. These results show that there are differences in the uptake of perfluorochemicals by certain rat lymphoid tissues and that immunological competence can be altered following administration of such materials.

Changes in intravascular fluid composition following blood replacement with perfluorocarbon emulsion in the rat

The effects of near total blood replacement with the proprietary perfluorocarbon emulsion, Fluosol-DA, have been examined in conscious, chronically catheterized rats. Animals survived for up to 48 h with a haematocrit of less than 2%. No overt changes in cardiovascular or respiratory functions occurred during blood replacement but thereafter, animals showed a progressive deterioration of haemodynamic control. Changes in intravascular fluid composition during and following exchange-transfusion have been monitored and the extent to which these changes could have contributed to the eventual disruption of homeostasis is discussed.

Perfluorochemicals as a treatment of decompression sickness in rats

Perfluorodecalin and perfluorotripropylamine which have N2 solubility coefficients of 28.4 and 35.7 ml/dl, respectively, were used for treatment of decompression sickness in this study. Rats with chronically implanted venous catheters were held for 30 min at 800 kPa (7 bar, 8 ATA) by introducing compressed air into a chamber in which they were kept; a relatively short period of decompression followed (200 kPa/min). Immediately thereafter injections of the perfluorochemicals (PFCs) in a dose of 10 g/kg were given, controls received saline in the same volume or remained without treatment. An observation period of 2 h followed; after this time the incidence of death amongst the experimental animals (as compared with controls tested by the chi 2-test) showed that PFC treatment increased the likelihood of survival. Probit-log time relationship for the incidence of death also revealed a significant decrease in lethality in treated rats 30 min after the end of decompression. The mean lethal times Lt50 differed significantly, too. A still greater effect might be expected if the PFC emulsion were deprived of its normal nitrogen content by oxygenation before administration. Under the conditions of the present experiments PFCs produced an improvement in N2 exhalation at least in terms of the survival rate after compression followed by a very short decompression time.