Catabolism of circulating enzymes: plasma clearance, endocytosis, and breakdown of lactate dehydrogenase-1 in rabbits
Lactate dehydrogenase-1, intravenously injected into rabbits, was cleared with first-order kinetics (half-life 27 min), until at least 80% of the injected activity had disappeared from plasma. Radioactivity from injected SVI-labeled enzyme disappeared at this same rate. Trichloroacetic-acid-soluble breakdown products started to appear in the circulation shortly after injection of the labeled enzyme. Body scans of the rabbits for 80 min after injection of T I-labeled enzyme revealed rapid accumulation of label in the liver, peaking 10-20 min after injection. Subsequently, activity in the liver declined and radioactivity (probably labeled breakdown products of low molecular mass) steadily accumulated in the bladder. Tissue fractionation of liver, 19 min after injection of labeled enzyme, indicated that the radioactivity was present both in endosomes and in lysosomes, suggesting uptake by endocytosis, followed by breakdown in the lysosomes. Measurements of radioactivity in liver and plasma suggest that the liver is responsible for the breakdown of at least 75% of the injected enzyme. Radioautography of tissue sections of liver and spleen showed accumulated radioactivity in sinusoidal liver cells and red pulpa, respectively. These results are very similar to those for lactate dehydrogenase-5, creatine kinase MM, and several other enzymes that we have previously studied in rats.
- Research Organization:
- Groningen Univ. (Netherlands)
- OSTI ID:
- 6611318
- Journal Information:
- Clin. Chem. (Winston-Salem, N.C.); (United States), Vol. 34:12
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LACTATE DEHYDROGENASE
CATABOLISM
AUTORADIOGRAPHY
BIOLOGICAL ACCUMULATION
BIOLOGICAL HALF-LIFE
BLOOD-PLASMA CLEARANCE
INTRAVENOUS INJECTION
IODINE 125
IODINE 131
LIVER
LYSOSOMES
PHAGOCYTOSIS
RABBITS
SWINE
TISSUE DISTRIBUTION
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CELL CONSTITUENTS
CLEARANCE
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
DISTRIBUTION
DOMESTIC ANIMALS
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
GLANDS
HEMIACETAL DEHYDROGENASES
INJECTION
INTAKE
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
MAMMALS
METABOLISM
NUCLEI
ODD-EVEN NUCLEI
ORGANOIDS
ORGANS
OXIDOREDUCTASES
RADIOISOTOPES
VERTEBRATES
550501* - Metabolism- Tracer Techniques