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 00:00:00 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), Vol. 36:3
• Country of Publication: United States
• Language: English

Related Subjects

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