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Biomedical subjects

Y Muto

Publications and source records attributed to Y Muto.

At least 523 records · Page 29Linked to original sources
PubMed1975

Vitamin A transport in chicken plasma: isolation and characterization of retinol-binding protein (RBP), prealbumin (PA), and RBP--PA complex.

Vitamin A-transporting protein in chicken plasma was purified by column chromatography on DEAE-Sephadex and Sephadex G-100; the protein formed a complex of retinol-binding protein (RBP) with prealbumin (PA). The molecular weight of the 1:1 molar complex was estimated to be 76,000 by gel filtration, and the sedimentation coefficient (S20,W) was found to be 5.2 S. RBP and PA were dissociated from the purified complex by means of CM-Sephadex column chromatography. Purified RBP contained 1 mole of vitamin A bound per mole of RBP. The molecular weight of RBP was determined to be 20,000 by gel filtration on Sephadex G-75, 19,000 by SDS-disc gel electrophoresis, and 20,500 by sedimentation equilibrium analysis. The S20,W was calculated to be 2.0 S. The molecular weight of PA was determined to be 56,000 by gel filtration, 52,000 by sedimentation equilibrium analysis, and 13,000 by SDS-disc gel electrophoresis. The S20,W was calculated to be 3.9 S. From these findings it was concluded that PA consists of four subunits, each with a molecular weight of approximately 13,000. Peptide mapping experiments suggested that the subunits were identical. No carbohydrates were detected in either RBP or PA. Chicken RBP and PA were immunologically distinct from those of human and rat. It is well established that vitamin A is transported bound to a specific plasma protein, retinol-binding protein (RBP), in both man (1,2) and rat (3). Purified human and rat plasma RBP have a single binding site for one molecule of retinol, alpha mobility on disc gel electrophoresis, and a molecular weight of approximately 20,000. In both species, RBP forms a tight complex with plasma prealbumin (PA) and normally circulates as a 1:1 molar protein-protein complex with PA (1-5). Despite these similarities, no immunological cross-reactivity between human and rat RBP has been observed (3,6). The present study was undertaken to explore whether or not a similar transport system for vitamin A exists in the chicken, a nonmammalian vertebrate. During the course of this study, Mokady and Tal (7) reported the isolation of RBP from chicken plasma and some physicochemical properties, e.g., a molecular weight of about 19,000. On the other hand, Muto, Smith, and Goodman (6) had already observed that the molecular weight of vitamin A-containing protein in fresh chicken plasma is approximately 60,000-80,000, as determined by gel filtration. However, no convincing information is available regarding an entire system of vitamin A transport in chicken plasma. We now describe procedures for the isolation of the RBA-PA complex of chicken plasma and the dissociation into the component proteins, RBP and PA. We also describe in detail the physicochemical properties of the individual proteins. It is also clearly demonstrated that chicken RBP and PA are immunologically distinct and different from the respective proteins in man and rat. Moreover, purified chicken PA appears to be a tetramer of four identical subunits and is thus similar to human and rat PA.

Amino Acid Sequence↗
PubMed1973

The plasma transport and metabolism of retinoic acid in the rat.

The transport of retinoic acid in plasma was examined in vitamin A-deficient rats maintained on small doses of radioactively labelled retinoic acid. After ultracentrifugation of serum adjusted to density 1.21, most of the radioactivity (83%) was associated with the proteins of density greater than 1.21, and not with the serum lipoproteins. Gel filtration of the labelled serum on Sephadex G-200 showed that the radioactive label was associated with protein in the molecular-weight range of serum albumin. On polyacrylamide-gel electrophoresis almost all of the recovered radioactivity migrated with serum albumin. Similar esults were obtained with serum from a normal control rat given a single oral dose of [(14)C]retinoic acid. These findings indicate that retinoic acid is transported in rat serum bound to serum albumin, and not by retinol-binding protein (the specific transport protein for plasma retinol). Several tissues and the entire remaining carcase of each rat were extracted with ethanol-acetone to determine the tissue distribution of retinoic acid and some of its metabolites. The total recover of radioactive compounds in in the entire body of the rat was about 7-9mug, representing less than 5% or 10% respectively of the total administered label in the two dosage groups studied. The results confirm that retinoic acid is not stored in any tissue. Most of the radioactive material was found in the carcase, rather than in the specific tissues analysed. Two-thirds of the radioactivity in the carcase appeared to represent unchanged retinoic acid. Of the tissues examined, the liver, kidneys and intestine had relatively high concentrations of radioactive compounds, whereas the testes and fat-pads had the lowest concentrations.

Adipose Tissue↗
PubMed1973

Comparative studies of retinol transport in plasma.

The comparative immunology and biochemistry of plasma retinol transport were studied using radioimmunoassays previously developed for human and for rat retinol-binding protein (RBP). Serum or plasma from 25 species of verebrates, from the mammalian orders Primates, Artiodactyla, Perissodactyla, Carnivora, and Rodentia and from the classes Aves, Amphibia, and Pisces, were assayed. There was a high degree of immunological specificity within a given mammalian order. Sera from seven subhuman primate species tested reacted in the human RBP immunoassay, and sera from four of five rodents reacted in the rat RBP immunoassay. Primate sera failed to react in the rat RBP immunoassay, and rodent sera failed to react in the human RBP immunoassay. Except for a slight reactivity of canine serum in the human RBP immunoassay, other sera showed no immunoreactivity. Using gel filtration, apparent molecular weights were estimated at 60,000-80,000 for the retinol transport systems in whole serum from cow, swine, chicken, and dog. Canine RBP was isolated and partially characterized. Purified canine RBP was generally similar to human and rat RBP with regard to molecular weight (approximately 20,000) and other properties. In plasma, canine RBP circulates as a protein-protein complex of higher apparent molecular weight. The complex remains to be characterized. These data suggest that mammals in general have a retinol transport system similar to the human and rat transport systems but that immunologically important differences in RBP occur among mammalian orders.

Amphibians↗