Rabbit Albumin Research Articles

The pharmacokinetics of an albumin-binding Fab (AB.Fab) can be modulated as a function of affinity for albumin

An AB.Fab (albumin-binding Fab) consists of a Fab and a phage-derived albumin-binding peptide. This molecule is capable of binding both antigen and albumin simultaneously. Using a Fab derived from Herceptin we generated a panel of AB.Fab variants with wide-ranging affinities for albumin. An assay that measured AB.Fab binding to albumin in solution was developed to most accurately reflect the binding affinity for albumin in vivo. Affinity varied depending upon the species of albumin tested. For rat and rabbit albumin, affinities ranged from 0.04 to 2.5 microM. Reduced affinity for albumin correlated with a reduced half-life and higher clearance rates in both species; the beta half-life ranged 6-fold while clearance ranged over 50-fold in rats and 20-fold in rabbits. To estimate the pharmacokinetic properties of an AB.Fab in humans, AB.Fab variants with similar affinities for rat and rabbit albumin were selected. Using their pharmacokinetic parameters and the principles of allometric scaling for albumin, we estimate an approximate beta half-life for an AB.Fab with 0.5 microM affinity for albumin of up to 4 days in humans with a clearance of 76 ml/h. These variants demonstrate the ability to modulate the clearance of a Fab fragment in vivo and help to establish guidelines for pharmacokinetic engineering of molecules through albumin binding.

Role of methionine residues of albumin in T-R conversion of hemoglobin

Hemoglobin (Hb) has peroxidase (POD)-like activity. We found that the addition of albumin to human Hb purified from venous erythrocytes increased its POD-like activity. We treated human Hb with a Blue-Toyopearl column of immobilized albumin, compared the treated Hb and native Hb for POD-like activity, the level of Hb-bound 2,3-diphosphoglycerate (2,3-DPG), and the absorption spectrum, and found that treatment with albumin released 2,3-DPG from Hb, resulting in a tense-relaxed (T-R) conversion and increased POD-like activity. The addition of human, mouse, rat, or bovine albumin to human Hb increased its POD-like activity. Addition of human albumin caused the highest increase, followed by that of mouse, rat, and bovine albumin in order. Addition of rabbit or guinea pig albumin caused little or no increase in the POD-like activity of Hb. Analysis of the distribution of methionine residues in the albumins of these animals showed that human, mouse, and rat albumins have a methionine residue at position 8 in loop 3 of domain I, and human and mouse albumins have an additional methionine residue in domain I. Bovine albumin has no methionine residue at position 8 in loop 3 of domain I, but has two methionine residues at other positions in domain I. Mouse and rat albumins have no methionine residues in domain I. These results suggest that the methionine residue at position 8 in loop 3 of domain I is most closely involved in the T-R conversion of human Hb. The addition of 2,3-DPG to albumin or selective oxidation of the methionine residues of albumin lessened the increase in POD-like activity when albumin was added to Hb, providing supporting evidence that the methionine residue of albumin is involved in the T-R conversion. The methionine residue of albumin may have a very important role in the degradation of Hb released from erythrocytes in blood vessels.

Raising Antibodies in Chickens Against Primaquine, Pyrimethamine, Dapsone, Tetracycline, and Doxycycline

Antibodies against primaquine, pyrimethamine, dapsone, tetracycline, and doxycycline were raised in chickens inoculated with each drug conjugated to a rabbit albumin carrier. Antibody titres against drug and carrier were highest during week 6 postinoculation. Affinity purified anti-primaquine antibodies did not recognise other drugs, but affinity purified anti-doxycycline and anti-tetracycline antibodies recognised both tetracycline and doxycycline in addition to primaquine. Primaquine was detected in urine from 6 to 12 hours after ingestion of therapeutic doses of the drug by anti-primaquine antibodies in a competitive ELISA. Affinity purified anti-primaquine antibodies detected primaquine in the cytoplasm and localised in organelles in monocytes that had been incubated with therapeutic concentrations of the drug.

Chemotaxis of oral treponemes toward sera and albumin of rabbit.

The motility and chemotaxis of human oral spirochetes Treponema denticola ATCC 35404, T. medium ATCC 700293, and T. vincentii ATCC 35580 were examined by a capillary assay method. Of five sera three human oral treponemes were dominantly chemoattractant to the rabbit serum. The checkerboard analysis of chemotaxis toward rabbit serum clearly showed that the motile T. denticola cells swam toward the culture media containing higher concentrations of the rabbit serum. T. denticola chemotaxis to the rabbit serum was clearly reduced by heating serum, and rabbit albumin contributed by 60 to 70% to its chemotaxis to the rabbit serum. Western blotting analysis demonstrated that these treponemes possessed rabbit albumin-binding polypeptides with approximate molecular sizes of 65 kDa and 70 kDa. Immunoelectron microscopy demonstrated that a 65 kDa rabbit albumin-binding polypeptide was located on the outer envelopes, suggesting that the rabbit albumin-binding polypeptide is responsible for chemotaxis toward rabbit serum.

Evaluation of [ 99mTc] liposomes as lymphoscintigraphic agents: comparison with [ 99mTc] sulfur colloid and [ 99mTc] human serum albumin

This study investigates the use of [ 99mTc] liposomes for the detection of sentinel lymph nodes. A variety of [ 99mTc] liposome formulations were compared with common lymphoscintigraphic agents including [ 99mTc] regular-sulfur colloid (SC), [ 99mTc] 0.22 μ-filtered-SC, [ 99mTc] reduced heating time 0.22 μ-filtered-SC, and [ 99mTc] human serum albumin (HSA) in rabbits. Images were acquired for the first 60 minutes and at 24 hours, followed by tissue biodistribution study. All agents except [ 99mTc] regular SC demonstrated good migration from the injection site. Agents were retained in the popliteal node at 24 hours to varying degrees as follows: both [ 99mTc] filtered SC preparations > [ 99mTc] regular SC > [ 99mTc] liposomes > [ 99mTc] HSA. [ 99mTc] liposome imaging can be used to develop novel liposome compositions with improved lymph node diagnostic and drug delivery characteristics.

Extra-hepatic expression of serum albumin mRNA in mouse retina

Purpose. In some mammals, serum albumin protein exists in the interphotoreceptor space (IPS), the space between photoreceptor cells and the retinal pigment epithelium. Serum albumin is synthesized largely in the liver, though low levels of extra-hepatic expression have been documented in several other tissues, including fetal rat kidney, pancreas, lung, and heart. The purpose of this study was to investigate whether serum albumin protein and mRNA are found in mouse retina. Methods. Using albumin rabbit antibodies and HRP goat anti-(rabbit IgG), we performed immunoassays on mouse IPS washes to detect the presence of serum albumin protein. Protein extracts from IPS washes were subjected to Affigel Blue chromatography. This resin has an affinity for serum albumin. Reverse transcription-polymerase chain reaction (RT-PCR) of retina total RNA was performed to search for albumin mRNA. Also, real-time reverse transcription polymerase chain reaction (RT-RT-PCR) was employed to look at the levels of expression in different age groups. Results. A constituent of the IPS washes specifically bound and eluted from Affigel Blue column, suggesting that the washes contained serum albumin. SDS PAGE revealed that the size of the constituent was 67 kDa, the size of serum albumin. This 67 kDa band reacted with mouse serum antibody. An RT-PCR amplified fragment of serum albumin mRNA from retina displayed the expected size. The sequence of this fragment is identical to authentic serum albumin cDNA sequence. RPE and choroid were negative for serum albumin mRNA. However, rd1 - /rd1 - retina was positive, suggesting that at least some serum albumin is synthesized in the inner layers of the retina. RT-RT-PCR showed that serum albumin mRNA levels in whole retina reached a maximum at about postnatal day 15 and gradually decreased to about one-sixth of maximum at 12 months age. Conclusions. Serum albumin protein and mRNA were found in mouse IPS and retina, suggesting that the protein is synthesized in the retina. The previously demonstrated ability of serum albumin to bind fatty acids and retinoids and its presence in the mouse IPS suggest a role for serum albumin in transporting retinoids in the retina or IPS, especially at young ages when concentrations appear greatest.

Sensitivity of Synthetic Surfactants to Albumin Inhibition in Preterm Rabbits

Surfactant can be inhibitedin vivoby plasma proteins invading the alveolar space during acute lung injury. The resistance to protein inhibition of surfactant preparations with various synthetic surfactant proteins B and C (B and C) was tested in preterm rabbits. Surfactants consisted of a palmitic acid containing phospholipid mixture (PL) with full-length SP-B peptide (B1-78), one of two SP-B mutants (Bserine and BR236C), the synthetic SP-B mimic KL4 (UCLA-KL4), a natural SP-B (Bbovine), synthetic palmitoylated SP-C peptide (C1-35), a combination of B1-78 + C1-35, a combination of BR236C + C1-35, and the clinical surfactant Survanta. Preterm rabbits born at 28 days of gestation were ventilated and received 100 mg/kg of albumin intratracheally at 30 min and 100 mg/kg of surfactant at 45 min after birth. Dynamic lung compliance (tidal volume/mean airway pressure) decreased from 0.82 to 0.57 mL/kg/cm H2O after albumin instillation and to 0.43 mL/kg/cm H2O over a 60-min period after saline placebo. Treatment with B1-78 + C1-35 and BR236C + C1-35 surfactant and Survanta returned dynamic compliance to prealbumin values, B1-78, BR236C, Bbovine, and C1-35 surfactant stabilized dynamic compliance, but PL, Bserine, and UCLA-KL4 surfactant were unable to prevent a further deterioration in dynamic compliance. These data suggest that a combination of synthetic surfactant peptides B1-78 and C1-35 and the clinical surfactant Survanta confer a high degree of resistance to surfactant inhibition by human albumin in ventilated preterm rabbits.

Streptococcal and staphylococcal superantigen-induced lymphocytic arteritis in a local type experimental model: Comparison with acute vasculitis in the arthus reaction

Many pathogenic bacteria produce superantigenic exotoxins. To study their pathogenetic role, in particular to test whether these toxins are able to induce vasculitis, we developed a local-type experimental model in rabbits. Toxins were injected along the intermediate auricular artery of the ear. The histology of ear skin, including the artery, was examined after single or repeated injections. Repeated injections of streptococcal erythrogenic toxins produced chronic-type arteritis characteristic of lymphocytic infiltration, whereas single injection induced no acute-type vasculitis. Staphylococcal enterotoxin B and toxic shock syndrome toxin-1 also induced the same type of arteritis, although weaker in degree. In human patients these lesions are similar to those of Kawasaki disease, a systemic vasculitis with unknown etiology. The Arthus reaction to human serum albumin in immunized rabbits included acute-type vasculitis similar to polyarteritis nodosa when examined in this model. Microvasculitis lesions similar to leukoclastic vasculitis were combined in the Arthus reaction but not in the superantigen-induced lesions. Our experimental model described here is widely applicable to the study of the etiology and pathogenesis of human diseases involving vasculitis lesions.

In vitro production of viable bovine blastocysts in media supplemented with rabbit-originated products

This study aimed at producing viable bovine blastocysts by IVM, IVF and IVC, in media without addition of bovine-originated products. Bovine serum albumin (BSA) was replaced by polyvinyl alcohol in washing media, fetal calf serum (FCS) by rabbit serum during maturation and culture, BSA by rabbit serum albumin in fertilization and culture media. The effect of substituting rabbit protein sources for bovine ones was tested on nuclear maturation, fertilization and developmental rates, and on the quality of the blastocysts obtained. The proportion of oocytes reaching metaphase II (MII) after maturation in TCM 199 containing epidermal growth factor was similar when supplemented with FCS (90/96) or with rabbit serum (92/99). The rate of 2 pronuclei formation was similar after sperm preparation and fertilization in Tyrode's medium supplemented with BSA (70/97) or rabbit albumin (70/94). In a third set of experiments, a total of 792 oocytes was matured, fertilized and cultured in media supplemented with bovine (standard) or rabbit products. Embryos were co-cultured with their own cumulus cells in synthetic oviduct fluid medium supplemented with serum at Day 3 post insemination. The proportion of cleaved and 5 to 8-cell stage embryos at Day 3 and the blastocyst yield on Day 8 were similar under standard and bovine additive-free conditions (cleavage: 81 vs 80 %, 5 to 8-cell stage: 49 vs 44%, blastocysts: 37 versus 30%). Blastocysts produced under bovine additive-free conditions were viable since a calf was born after the transfer of a frozen embryo. Replacement of bovine products by rabbit originating ones resulted in a 0.5-d delay in blastocyst detection. Day 8 blastocysts produced in media containing rabbit products had a significantly lower number of cells (101 ± 7) than those produced under standard conditions (120 ± 6), possibly because of the difference in blastocyst age. In conclusion, the protocol presented here allows for the efficient production of viable bovine blastocysts under conditions that reduce the risk of disease transmission.

Rescue of Preterm Rabbits from Surfactant Inhibition with Synthetic Surfactant. † 1545

Surfactant can be inhibited in vivo by plasma proteins invading the alveolar space during acute lung injury. We tested the resistence of surfactant preparations with synthetic peptides against inhibition by human albumin in preterm rabbits. Surfactant preparations studied included a standard phospholipid mixture (PL), PL with 3% surfactant peptide B1-78(B), PL with 3% surfactnat peptide B1-78 and 1% palmitoylated surfactant peptide C1-35 (BC), PL with 3% KL4 peptide(KL4), and Survanta®. Preterm rabbits born at 28 d gestation were intubated and placed in a temperature-controlled ventilator-plethysmography system with 100% oxygen and a positive end-expiratory pressure of 3 cm H2O. Peak inspiratory pressure was adjusted individually to achieve tidal volumes of 6-7 ml/kg as measured with a pneumotachometer. Rabbits received 100 mg of human albumin intratracheally at 30 min, followed by 100 mg/kg of surfactant at 45 min, and were killed and lavaged at 105 min. Groups consisted of 5-8 animals. Mean dynamic compliance decreased from 0.56 to 0.40 ml/kg/cm H2O after albumin instillation. Sixty min after surfactant treatment, dynamic compliance was 82% of the post-albumin values in rabbits treated with BC, 63% with Survanta, 59% with KL4, 53% with B, and 48% with PL. Protein content of the lung lavages was lowest after BC, intermediate after KL4, B, and PL, and highest after Survanta treatment. These data suggest that a combination of synthetic surfactant peptides B and C confers a high degree of resistence against surfactant inhibition by human albumin in ventilated preterm rabbits.

Inhibition of Glutamate Uptake Causes an Acute Increase in Aqueous Humor Protein

Inhibition of glutamate transport has been shown to increase paracellular permeability of epithelial cell monolayersin vitro. To determine if blocking glutamate transport would affect tissue permeabilityin vivo,D-aspartate (D-Asp; 300 nmol 30 μl−1) (a non-toxic competitive inhibitor of glutamate transport) or a placebo was injected into the anterior chambers of the fellow eyes of 15 adult rabbits. [14C]-L-glucose and/or [125I]-rabbit albumin were included in the injection vehicle as aqueous humor (AH) outflow markers. The specific inhibition of glutamate uptake byD-Asp was indicated by a 15% increase in AH glutamate (174±9 nmol ml−1to 205±13 nmol ml−1;P=0.03) at 1–1.5 hr post injection. Also, the efflux of [14C]-L-glucose and [125I]-rabbit albumin from the AH of D-Asp injected eyes was increased 22% over the placebo-injected control eyes (P≤0.02). Concomitantly, the total protein concentration in the AH fromD-Asp injected eyes (517±35 μg ml−1) was 19% greater (P<0.02) than the protein concentration in AH from placebo-injected control eyes (420±36 μg ml−1). In additional studies, an irreversible inhibitor of glutamate transport, threo-β-hydroxyaspartate (THA; 30 nmol 30 μl−1), was shown to increase the efflux of [14C]-L-glucose (22%;P<0.05) from the anterior chamber and increase AH protein concentrations by 29% (484±112 μg ml−1in control AH versus 686±117 μg ml−1in THA AH,P=0.08) at 1 hr post intracameral injection. SDS-PAGE analysis of the AH associated the protein increase in theD-Asp and THA injected eyes but not placebo-injected control eyes with a detectable increase in a 66 kDa protein (aligns with serum albumin) and several lower molecular weight (23–35 kDa) AH proteins. The results found suggest that inhibition of glutamate transport from the AH acutely increases intraocular epithelial/endothelial paracellular permeability.

An l-amino acid electrode for monitoring beer fermentation

A membrane covered amperometric l-amino acid electrode is described, employing l-amino acid oxidase immobilized on a Pt disc electrode with rabbit albumin and glutaraldehyde. The electrode response to a range of l-amino acids and a theoretical treatment for the rate determining step are presented. Results are also given for the application of the electrode in monitoring beer fermentations. Appropriate amino acid utilisation is vital for both yeast cell growth and beer flavour development.

Effect of endocytosis inhibitors on alveolar clearance of albumin, immunoglobulin G, and SP-A in rabbits

Protein in the alveolar space may be cleared by endocytosis and degradation inside alveolar epithelial cells, by transcytosis across the alveolar epithelium, or by restricted diffusion through the epithelium. The relative contributions of these three pathways to clearance of large quantities of protein from the air spaces is not known. This study investigated the effects of monensin and nocodazole, agents which inhibit endocytosis in cell culture, on alveolar epithelial protein transport in anesthetized rabbits. There was evidence that monensin and nocodazole inhibited endocytosis by the alveolar epithelium in vivo. Nocodazole increased the number of vesicles in the alveolar epithelium and capillary endothelium. Monensin increased vesicle density in the endothelium. These results suggested that the inhibitors disrupted microtubules or interrupted cellular membrane traffic in the lung. Both inhibitors decreased lung parenchymal uptake of immunoreactive human albumin from the air spaces. Monensin and nocodazole inhibited albumin uptake in cultured alveolar type II cells. Monensin increased the amount of 125I-labeled surfactant protein A associated with the lungs, compared with the quantity remaining in the air space 2 h after instillation. Although the drugs decreased alveolar epithelial protein uptake, they did not decrease alveolar clearance of 125I-labeled immunoglobulin G or 131I-labeled albumin in anesthetized rabbits. Thus monensin- and nocodazole-sensitive protein-uptake pathways do not account for most alveolar protein clearance when the distal air spaces are filled with a protein solution.

Transvascular albumin flux in rabbit hindlimb after tourniquet ischemia.

Transvascular clearance of labeled rabbit albumin was measured in gastrocnemius muscle and heel skin from anesthetized rabbits after 1 or 2 h of tourniquet ischemia. Albumin clearance, calculated as a 1-h extravascular uptake, was 4.7 +/- 0.4 and 29 +/- 1 microliter.h-1 x g dry wt-1 for control gastrocnemius muscle and heel skin, respectively. During the first hour of reperfusion, the clearance was 101 +/- 23 and 56 +/- 6 microliters.h-1 x g dry wt-1 in the muscle and skin, respectively. The clearance in skin during the second and third hour of reperfusion was not different from control. The increased clearance in muscle persisted during 2 h of reperfusion but returned to control levels during the third hour of reperfusion. The solvent drag reflection coefficient was measured by increasing venous pressure during reperfusion in one leg after bilateral ischemia. In skin, the reflection coefficient, calculated as 1 minus the change in clearance divided by the change in water weight, was 0.94 +/- 0.05 and did not change with tourniquet ischemia. The reflection coefficient in muscle was 0.98 +/- 0.01 for control animals and decreased to 0.66 +/- 0.11 during the first hour of reperfusion. The reflection coefficient was not different from control during the third hour of reperfusion. The transitory increase in microvascular permeability to albumin in skeletal muscle is more indicative of an acute inflammatory response than of endothelial injury.

Factors affecting inorganic mercury transport and toxicity in the isolated perfused proximal tubule.

The effects of cysteine (80 microM), glutathione (80 microM), rabbit albumin (100 microM), and an ultrafiltrate of rabbit plasma on the toxicity and transport of inorganic mercury (Hg2+; 18.4 microM) in isolated perfused S1, S2, and S3 segments of the renal proximal tubule from the rabbit were studied. Cellular and tubular injuries were assessed qualitatively by light microscopy observations and quantitatively by the tubular leak of the volume marker 3H-glucose. The lumen-to-bath transport of inorganic mercury was assessed by measuring both the rate of disappearance of inorganic mercury from the luminal fluid and the rate of appearance of inorganic mercury in the bath. When glutathione was added to the perfusate containing the inorganic mercury, no signs of epithelial cell necrosis or injury were detected in any of the three segments of the proximal tubule. There was also an absence of or a decrease in cellular injury in the epithelium of the same tubular segments when either cysteine or the ultrafiltrate was present in the perfusate. However, when rabbit albumin and inorganic mercury were present in the perfusate, severe degenerative and necrotic changes occurred very rapidly in the epithelium of all three segments of the proximal tubule. In almost every instance where glutathione, cysteine, or the plasma ultrafiltrate were present in the perfusate, the disappearance flux of inorganic mercury from the tubular lumen into the tubular epithelium was lowered. It was concluded that glutathione, cysteine, and the ultrafiltrate of rabbit plasma provide isolated perfused S1, S2, and S3 segments of the proximal tubule varying degrees of protection from the toxic effects of inorganic mercury. This protection appears to be related to a decrease in the movement of inorganic mercury across the luminal membrane of the tubular epithelial cells.

The effect of intravascular complement activation and brief episodes of hypoxia on protein in bronchoalveolar lavage fluid in C5 sufficient and deficient mice

Our earlier investigations indicated that systemic complement activation with iv cobra venom factor (CVF) or infused zymosan-activated rabbit plasma or rabbit C5a does not significantly increase bronchoalveolar lavage albumin in rabbits (Am Rev Respir Dis 1982; 125:335-340); but that complement activation due to CVF combined with a brief episode of hypoxia increases lavage albumin and is associated with the presence of neutrophils for its expression (J Clin Invest 1985; 75:902-910). In order to determine if intravenous CVF and hypoxia cause similar alterations in mice, and to investigate the time course of the response as well as the importance of C5 fragments to the process, we challenged the B10.D2/nSn strain of C5 sufficient mice (C5+) and the congenic B10.D2/oSn strain of C5 deficient mice (C5-) with intravenous CVF, 15 min of 12% oxygen, or CVF followed by hypoxia. Neither C5+ nor C5- mice had significant increases in lavage protein after either CVF or hypoxia. However, the combined insults significantly increased lavage protein in C5+ but not C5- mice; polyacrylamide gel electrophoresis showed increased amounts of proteins of low and high molecular weights in lavage fluid from the C5+ strain. While the time course of abnormalities in mice was different from that in rabbits, both meclofenamate pretreatment and neutrophil depletion attenuated the increases in lavage protein after the combined insults in both animal species. Infusion of prostaglandin E2 (PGE2) with CVF in the C5+ mice also led to significant increases in lavage protein. We conclude that in mice, intravenous complement activation, as an isolated event, does not cause a significant increase in lavage protein.(ABSTRACT TRUNCATED AT 250 WORDS)

The interaction of cefotaxime with the serum albumin of several mammalian species

1. The interaction of cefotaxime with the serum albumin of several mammalian species; horses, swine, sheep, dogs and rabbits, was studied comparatively. The technique of ultrafiltration and spectrophotometric determination of the free antibiotic in the filtrate was used. 2. Binding percentages, which vary according to the species studied, were found to be higher in swine and rabbit albumins (between 92 and 81%) and lower for sheep, dog and horse albumins (between 67 and 52%). 3. The number of binding sites is usually close to 2; in the case of the horse it is 2.43. The apparent binding constants are: swine, 1.61 × 10 4 M −1; rabbit, 1.19 × 10 4 M −1; sheep, 2.33 × 10 3 M −1; dog, 2.00 × 10 3 M −1; horse, 1.42 × 10 3 M −1. The Scatchard model was used for data analysis. 4. Possible consequences of this interaction regarding clinical use of cefotaxime on different species are discussed.

Initial equilibration of albumin and IgG in rabbit hind paw skin and lymph

To determine if the interstitial distribution of plasma proteins influences transport from plasma to lymph, the initial plasma-to-extravascular and plasma-to-lymph equilibrations for 131I-labeled rabbit albumin and 125I-labeled rabbit IgG were compared in hind paw heel skin of anesthetized New Zealand White rabbits. Plasma specific activities were maintained constant with time using continuous infusions. The plasma space in skin samples taken at the end of the experiment was estimated by a 3-min accumulation of 59Fe-labeled bovine transferrin. Albumin and IgG concentrations in plasma, lymph, and skin were determined by rocket electroimmunoassay. The lymph specific activity relative to that of plasma for the larger sized IgG was significantly greater ( P < 0.01) than that for albumin during the initial 8 hr of equilibration. The tissue specific activity relative to that of plasma for IgG was significantly less ( P < 0.01) than that for albumin. The distribution space at lymph concentration for both proteins was 1 ml/g dry skin wt, indicating similar excluded volumes. These data are consistent with the hypothesis that convective movement of plasma proteins through the interstitium affects lymph equilibration while diffusion affects tissue equilibration.

Intraocular Irrigating Solutions and Permeability of the Blood-Aqueous Barrier

The effects of intraocular irrigating solutions on the blood-aqueous barrier were studied using rabbits injected with fluorescein isothiocyanate-labeled rabbit albumin. Two days after the injection, the anterior chamber was perfused for 121 minutes with one of the following solutions: normal saline, a commercially available citrate-acetate bicarbonate solution, or a glucose glutathione bicarbonate solution; the amount of fluorescein isothiocyanate-labeled rabbit albumin collected in the outflowing perfusate standardized to its plasma concentration was adopted as a blood-aqueous barrier permeability index. Of the three solutions, normal saline showed the highest permeability index and glucose glutathione bicarbonate solution showed the lowest. The effects of oxidized glutathione on the blood-aqueous barrier were also studied, using solutions containing various concentrations of oxidized glutathione. The permeability index for the solution containing 0.3 mmol/L of oxidized glutathione was significantly smaller than that for the solution without oxidized glutathione, suggesting that oxidized glutathione has a beneficial effect on the integrity of the blood-aqueous barrier.

Cornea fluid dynamics II. Evidence for transport of radiolabelled albumin in rabbits by bulk flow

Transport of radiolabelled albumin in vivo has been measured in cornea. In anaesthetized rabbits, a 1–10 nl mixture of either 125I- or 131I-labelled human serum albumin and fluorescinthiocarbamoyldextran was injected with micropipettes under guidance of a fluorescent microscope. The injection sites were a spot 3 mm from limbus and the cornea centre, and the sites were localized by a template fitting the cornea exactly. Four, 12, 20 and 30 hr after the injection, the rabbits were reanaesthetized, and enucleated after being killed with an overdose of anaesthetic. The bulbi were frozen, and dissection of cornea performed in the cold room using the template described above and a stereomicroscope. Numbered samples were obtained, and isotope distribution measured. In the experiments lasting for 20 hr, about 55% of the isotope was recovered, giving a transfer coefficient of 0·4-0·5 per day. A common pattern of isotope distribution was observed independant of duration of isotope equilibration; peripherally injected isotope moved preferentially in central direction, indicating that fluid is transported by bulk flow and diffusion from peripheral to central cornea. Centrally injected isotope moved symmetrically from the injection point, as expected from transport by diffusion alone. Data from experiments with isotope injection in the cornea centre allowed the calculation of a diffusion coefficient for albumin along cornea of 2·19 × 10 −7 cm 2 sec −1.