Metabolism of glycosylated human salivary amylase: in vivo plasma clearance by rat hepatic endothelial cells and in vitro receptor mediated pinocytosis by rat macrophages

Journal Article · Sat Sep 01 04:00:00 EDT 1984 · J. Leukocyte Biol.; (United States)

OSTI ID:5808813

Niesen, T E; Alpers, D H; Stahl, P D; Rosenblum, J L

Salivary-type amylase normally comprises about 60% of the amylase activity in human serum, but only a small fraction is a glycosylated isoenzyme (amylase A). In contrast, 1/3 of amylase in human saliva is glycosylated. Since glycosylation can affect circulatory clearance, we studied the clearance of amylase A in rats and its uptake by rat alveolar macrophages. Following intravenous injection, /sup 125/I-labeled amylase A disappeared rapidly from plasma (t 1/2 . 9 min) and accumulated in the liver. Simultaneous injection of mannose-albumin slowed its clearance to a rate comparable to that of /sup 125/I-labeled nonglycosylated salivary amylase (t 1/2 . 45 min). In contrast, galactose-albumin had no effect. Electron microscope autoradiography of the liver following injection of /sup 125/I-labeled amylase A revealed a localization of grains over the hepatic endothelial cells. In vitro studies indicated that amylase A is taken up by alveolar macrophages via receptor-mediated pinocytosis. Uptake was linear over time, saturable, and inhibited by mannan and mannose-albumin, but not by galactose-albumin. We conclude that amylase A, which is a naturally occurring human glycoprotein with at most three terminal L-fucose residues per molecule, is recognized in rats by a mannose receptor located on hepatic endothelial cells. We speculate that this receptor, by rapidly clearing circulating amylase A, may be responsible for the low level of amylase A in human serum.

• Research Organization: Washington Univ. School of Medicine, St. Louis, MO
• OSTI ID: 5808813
• Journal Information: J. Leukocyte Biol.; (United States), Journal Name: J. Leukocyte Biol.; (United States) Vol. 36:3
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
AMYLASE
ANIMAL CELLS
ANIMALS
AUTORADIOGRAPHY
BETA DECAY RADIOISOTOPES
BIOLOGICAL ACCUMULATION
BIOLOGICAL LOCALIZATION
BIOLOGICAL MATERIALS
BLOOD-PLASMA CLEARANCE
BODY
BODY FLUIDS
CARBOHYDRATES
CLEARANCE
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ENZYME ACTIVITY
ENZYMES
GLANDS
GLYCOSYL HYDROLASES
HEXOSES
HYDROLASES
IN VITRO
IN VIVO
INJECTION
INTAKE
INTERMEDIATE MASS NUCLEI
INTRAVENOUS INJECTION
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIVER
MACROPHAGES
MAMMALS
MAN
MANNOSE
MATERIALS
METABOLISM
MONOSACCHARIDES
NUCLEI
O-GLYCOSYL HYDROLASES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PHAGOCYTES
PRIMATES
RADIOISOTOPES
RATS
RECEPTORS
RODENTS
SACCHARIDES
SALIVA
SOMATIC CELLS
TRACER TECHNIQUES
UPTAKE
VERTEBRATES