Synthesis, transport, and secretion of plasma proteins by the livers of control and Streptococcus pneumoniae-infected rats

Abstract

The synthesis, intracellular transport, and secretion of plasma proteins by the liver was studied in both control and Streptococcus pneumoniae-infected rats. Rats were injected with [3H]leucine; at various time intervals, the components of the intracellular secretory system were isolated. The isolation and partial characterization of rough microsomes, smooth microsomes, and Golgi from both control and infected animals are described. After infection, the specific activity of the label in the homogenate and in all isolated cell fractions was significantly increased. In both control and infected animals, the kinetics of labeling suggested that the secretory pathway of the newly synthesized protein was from the rough endoplasmic reticulum to the smooth endoplasmic reticulum to the Golgi and finally to the circulation. Even though infected animals synthesized, transported, and secreted significantly more plasma protein, infection did not significantly alter the secretion time (time between injection of isotope and appearance of labeled protein in the circulation). It is concluded that, after S. pneumoniae infection, the liver still maintains its capability to perform the basic functions of protein synthesis, intracellular transport, and seretion and that newly synthesized plasma protein follows the same intracellular pathway in both control and S. pneumoniae-infected rats.

Elevated glycosyltransferase activities in infected or traumatized hosts: nonspecific response to inflammation

“…2). DISCUSSION The elevated glycosyltransferase values in livers of septic rats were not unexpected, considering the markedly increased rates of hepatic synthesis and secretion of serum glycoproteins which characterize an infectious process (6,17,24,33). Clinical states associated with tissue trauma, including neoplasia, myocardial infarction, burns, and sterile inflammatory lesions, also engender a nonspecific anabolic response on the part of the liver, resulting in the synthesis of a class of glycoproteins collectively termed acute-phase globulins (17,24,28,33).…”

“…Rats inoculated with 105 S. pneumoniae uniformly succumb to the infection with a mean time to death of about 66 h (17). Rats became febrile within 12 to 16 h and at 24 h showed characteristic signs of acute infection, including fever, bacteremia, modulation of the concentration of serum metals, and an increase in the acute-phase protein, a2-macrofetoprotein (Table 1).…”

“…A blank was run simultaneously in which enzyme was replaced by water. After an appropriate period of incubation, reactions were terminated by pipetting 40 pJ of the mixture onto strips of trichloroacetic acid-treated Whatman 3MM chromatography paper, washed, and counted by scintillation spectroscopy (17).…”

Depression of Intestinal Lysosomal β‐Glucuronidase and Acid Phosphatase Activities by Gastrointestinal Microorganisms

“…This will be investigated in additional experiments. S. pneumoniae infection alters not only the enzyme complement of hepatic organelles, but also their number and density (7). ALP, which is a marker enzyme of the hepatic plasma membrane, was detected in rough and smooth microsomes of the liver in rats infected with S. pneumoniae (7).…”