Biomaterial Database

Studies on the turnover of exogenous mannose-terminal glucocerebrosidase in rat liver lysosomes. 1995

G J Murray, and K L Oliver, and F S Jin, and R O Brady

Developmental and Metabolic Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.

Mannose-terminal glucocerebrosidase prepared by exoglycosidase digestion of human placental glucocerebrosidase is reported effective in the treatment of patients with type 1 Gaucher's disease [Barton et al. (1991); N Engl J Med 324:1464-1470]. However, the amount of enzyme that is necessary for therapeutic effect is much higher than would be predicted from in vitro activity measurements. We have investigated the fate of infused enzyme following intravenous administration in Sprague-Dawley rats. In this model system, the enzyme is rapidly cleared from the plasma compartment by receptor-mediated endocytosis via the mannose-specific receptor present on reticuloendothelial cells. Enzyme activity measured in rat liver biopsy specimens at various times post-infusion revealed a rapid initial loss of approximately one-half of the maximum delivered enzyme in the first hour followed by a slower decay with a half-life of approximately 6-8 h. The loss in enzyme activity is paralleled by a loss in enzyme protein when analyzed by Western blots. There is no evidence for return of enzyme activity or inactive enzyme protein to the plasma. Incomplete integration into the lysosomal membrane was demonstrated by the use of differential extraction of purified rat liver lysosomes to distinguish between lumenal and membrane bound enzyme. Immunoelectron microscopy of rat liver following infusion of mannose-terminal glucocerebrosidase confirmed localization of the delivered enzyme primarily within the lumen of the lysosomes of Kupffer cells and to a lesser extent associated with the lysosomal membrane. Enzyme activity was stable in isolated rat liver lysosomes preloaded with mannose-terminal glucocerebrosidase and incubated in the absence or presence of ATP. Acidification of the lysosomes to pH 3 results in a rapid loss of enzyme activity and protein; however, the relationship between the in vitro loss and the loss in enzyme activity in intact liver is not clear. We conclude from these studies that rapid intracellular degradation of administered glucocerebrosidase is the prime factor responsible for the high dose required for effective treatment of Gaucher's disease.

UI	MeSH Term	Description	Entries
D007262	Infusions, Intravenous	The long-term (minutes to hours) administration of a fluid into the vein through venipuncture, either by letting the fluid flow by gravity or by pumping it.	Drip Infusions,Intravenous Drip,Intravenous Infusions,Drip Infusion,Drip, Intravenous,Infusion, Drip,Infusion, Intravenous,Infusions, Drip,Intravenous Infusion
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D008247	Lysosomes	A class of morphologically heterogeneous cytoplasmic particles in animal and plant tissues characterized by their content of hydrolytic enzymes and the structure-linked latency of these enzymes. The intracellular functions of lysosomes depend on their lytic potential. The single unit membrane of the lysosome acts as a barrier between the enzymes enclosed in the lysosome and the external substrate. The activity of the enzymes contained in lysosomes is limited or nil unless the vesicle in which they are enclosed is ruptured or undergoes MEMBRANE FUSION. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed).	Autolysosome,Autolysosomes,Lysosome
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D010920	Placenta	A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (CHORIONIC VILLI) derived from TROPHOBLASTS and a maternal portion (DECIDUA) derived from the uterine ENDOMETRIUM. The placenta produces an array of steroid, protein and peptide hormones (PLACENTAL HORMONES).	Placentoma, Normal,Placentome,Placentas,Placentomes
D011247	Pregnancy	The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.	Gestation,Pregnancies
D002458	Cell Fractionation	Techniques to partition various components of the cell into SUBCELLULAR FRACTIONS.	Cell Fractionations,Fractionation, Cell,Fractionations, Cell
D002501	Centrifugation, Zonal	Centrifugation using a rotating chamber of large capacity in which to separate cell organelles by density-gradient centrifugation. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Centrifugations, Zonal,Zonal Centrifugation,Zonal Centrifugations
D005260	Female		Females