Impairment of albumin synthesis in cell‐free systems from rat liver

Albumin and transferrin synthesis during development in the rat

“…The results obtained by Schreiber and co-workers (Schreiber et al, 1969;Maeno et al, 1970) may be due to non-specific adsorption oflabelled compounds to chromatography paper discs and to the fact that albumin is probably synthesized as a precursor, proalbumin, which differs chemically from albumin but is precipitated by antiserum against albumin, and which is subsequently converted into albumin within the liver cell (Judah et al, 1973;Russell & Geller, 1973). The shoulder in the albumin radioactivity peak which was found in two of the sodium dodecyl sulphate-polyacrylamide-gel-electrophoresis runs performed in the present work may represent this proalbumin.…”

“…Validation of the immunoprecipitation technique This study was undertaken to obtain information on the synthesis of the serum proteins, transferrin and albumin, in the embryo and during the neonatal period. The method used to isolate the proteins, immunoprecipitation of a mixture of intracellular and extracellular proteins, may be questioned on the basis of the results of Schreiber and his co-workers (Schreiber et al, 1969;Maeno et al, 1970). They found that immunoprecipitation of liver proteins on chromatography paper discs did not yield radiochemically pure albumin, and suggested that this may be due to the co-precipitation of radioactive compounds which were not covalently bound to albumin.…”

“…The following investigation of the immunoprecipitation procedure was undertaken because of evidence that immunological precipitation ofalbumin from the liver on to chromatography paper discs does not yield radiochemically pure albumin (Schreiber et al, 1969;Maeno et al, 1970). Albumin immunoprecipitates from livers of foetal (21 day) and adult rats were prepared as described above, air-dried and then dissolved by incubation at 45°C for 1 h in 0.1 ml of a solution of 6M-urea, 1 % (w/v) sodium dodecyl sulphate, 1 % 2-mercaptoethanol, 0.1 M-sodium phosphate (pH 7.2).…”

The synthesis and secretion of albumin

“…Albumin is usually believed to be a protein which can be easily purified; however, in studies on albumin synthesis in liver, hepatomas, and cell-free systems, radiochemically pure albumin was very difficult to obtain Rotermund et al, 1970;Maeno et al, 1970;Judah and Nicholls, 1971a;Schreiber, 1972).…”

“…It was converted into albumin in vitro by trypsin treatment, with the concomitant release of a small arginine-containing peptide (Judah et al, 1973). Thus, whereas the early studies seemed to suggest.that serum albumin and its intraceUular precursor(s) were chemically identical (Peters, 1959), the separation of albumin-like protein(s) and albumin by electrophoresis, ion-exchange chromatography (Decken, 1963b;Schreiber et al, 1969;Rotermund et al, 1970;Maeno et al, 1970;Judah and Nicholls, 1971a;Urban et al, 1974b), or isoelectric focusing (Geller et al, 1972;Quinn et al, 1975), as well as the tryptic conversion of albumin-like protein into albumin (Judah et al, 1973), were better explained by assuming a difference in the chemical structure of albumin and its precursor(s). This difference did not seem to be in the N-terminal amino acid of the molecule as Russell and Geller (1973) reported the N-terminal amino acid of both the albumin-like protein and albumin to be glutamate (or glutamine).…”