Human β-GIucuronidase. II. Fate of Infused Human Placental β-Glucuronidase in the Rat

A B S T R A C T The cellular location and carbohydrate specificities of a glycoprotein recognition system on rat hepatic sinusoidal cells have been determined. Purified preparations of endothelial, Kupffer, and parenchymal cells were prepared by collagenase liver perfusion, centrifugation on Percoll gradients, and centrifugal elutriation. '251-labeled agalactoorosomucoid, an N-acetylglucosamine-terminated glycoprotein, was selectively taken up in vitro by endothelial cells. Uptake was shown to be protein dependent, calcium ion dependent, and saturable, and could be described by Michaelis-Menten kinetics (apparent Km 0.29 ,M; apparent maximum velocity 4.8 pmol/h per 5 X 106 cells). Uptake was inhibited not only by Nacetylglucosamine, mannose, and mannan but also by glucose, fructose, and a glucose-albumin conjugate. Inhibition by glucose was competitive over a wide range of concentrations and was almost 100% at a glucose concentration of 56 mM. Fasting and the induction of diabetes mellitus prior to isolation of cells was associated with 60% reductions in the recovery of endothelial cells. Uptake by cells isolated from fasted rats was enhanced (apparent maximum velocity 14.3 pmol/ h per 5 X 10 cells without change in the apparent K.).These observations suggest that fasting is associated with a marked increase in the mean number of glycoprotein receptors per endothelial cell isolated from normal rats. This effect of fasting could be due to upregulation of glycoprotein receptors on endothelial cells or to the selective isolation of a subpopulation of endothelial cells from fasted animals that bears more glycoprotein receptors per cell than does another sub-

Section: Uptake Of Glycoproteins By Hepatic Cellssupporting

confidence: 80%

mentioning

confidence: 99%

Modulation of a Glycoprotein Recognition System on Rat Hepatic Endothelial Cells by Glucose and Diabetes Mellitus

Summerfield¹,

Vergalla²,

Jones³

1982

“…This may relate to differences in developmental regulation of various cell surface receptors in liver (e.g., the asialoglycoprotein receptor on hepatocytes (33), the mannose receptor on Kupffer cells (24,25), and the Man 6-P receptor (34, 35) on both cell types), and might also be influenced by the changing weight-dependent dosage received over the course ofthe injections. It will be interesting to determine the distribution of the enzyme when a weight adjusted dose comparable to that given in the newborn is administered to the 5-wk-old adult animal.…”

Section: Discussionmentioning

confidence: 99%

Enzyme replacement therapy for murine mucopolysaccharidosis type VII.

Sands

Vogler²,

Kyle³

et al. 1994

196

137

Recombinant mouse el-glucuronidase administered intravenously to newborn mice with mucopolysaccharidosis type VII (MPS VII) is rapidly cleared from the circulation and localized in many tissues. Here we determine the tissue distribution of injected enzyme and describe its effects on the histopathology in 6-wk-old MPS VII mice that received either one injection of 28,000 U recombinant 5-glucuronidase at 5 wk of age or received six injections of 28,000 U given at weekly intervals beginning at birth. These mice were compared with untreated 6-wk-old MPS VII mice. The single injection decreased lysosomal distention in the fixed tissue macrophage system. MPS VII mice that received multiple injections had 27.8, 3.5, and 3.3% of normal levels of f-glucuronidase in liver, spleen, and kidney, respectively. Brain had detectable f-glucuronidase, ranging from 2.0-12.1% of normal. Secondary elevations of agalactosidase and fl-hexosaminidase in brain, spleen, liver, and kidney were decreased compared with untreated MPS VII mice. Although no improvement was observed in chondrocytes, glia, and some neurons, the skeleton had less clinical and pathological evidence of disease and the brain had reduced lysosomal storage in meninges and selected neuronal groups. These data show that recombinant f-glucuronidase treatment begun in newborn MPS VII mice provides enzyme to most tissues and significantly reduces or prevents the accumulation of lysosomal storage during the first 6 wk of life. Whether therapy begun later in life can achieve this level of correction remains to be established.

“…The changes in urinary glycosaminoglycans noted in these patients were transient, presumably because most lysosomal enzymes have relatively short halflives intracellularly (10)(11)(12). Studies on enzymes present in aimniotic fluid (13), leukocyte homogenates (14), anid serum (15), however, generally indicate a higher degree of stability.…”

Section: Introductionmentioning

confidence: 95%

Enzyme replacement therapy by fibroblast transplantation: long-term biochemical study in three cases of Hunter's syndrome.

Dean¹,

Stevens²,

Muir³

et al. 1979

A B S T R A C T We have assessed the effectiveness of transplanted histocompatible fibroblasts as a long-lived source of lysosomal enzymes for replacement therapy in three patients with Hunter's syndrome, over periods ranging from 2.5 to 3.75 yr. The level of Hunter corrective factor excreted by all three patients increased after transplantation, as did the activity of a-L-idurono-2-sulfate sulfatase in serum, when measured directly with a radioactive disulfated disaccharide substrate. Sulfatase activity was also raised in leukocyte homogenates from the two patients that we were able to assess. These increases in enzyme activity were accompanied by corresponding increases in catabolism of heparan and dermatan sulfates, as shown by (a) a decrease in sulfate:uronic ratios of urinary oligosaccharides, (b) an increase in iduronic acid monosaccharide, and (c) a normalization of Bio-Gel P-2 gel filtration profiles. Both the increase in enzyme activity and increased catabolism were maintained during the period of study and were not affected by either a gradual decrease or total withdrawal of immunosuppressive therapy.