Validation of in vivo receptor measurements via in vitro radioassay: technetium-99m-galactosyl-neoglycoalbumin as prototype model.
Hepatic binding protein (HBP) is a hepatocyte-specific receptor for serum asialoglycoproteins. The receptor also recognizes a synthetic glycoprotein that has been developed as a radiopharmaceutical, technetium-99m-galactosyl-neoglycoalbumin (99mTc-NGA). This report describes the correlation between receptor parameters measured in vivo via kinetic modeling of 99mTc-NGA and those measured by in vitro radioassay of biopsied liver tissue. Eleven patients with diffuse hepatic disease underwent percutaneous liver biopsy followed by a 99mTc-NGA functional imaging study. In vivo measurements of HBP quantity Ro and forward binding rate constant kb obtained from the kinetic analysis of 99mTc-NGA liver and blood time-activity data were compared to total receptor quantity and the HBP-99mTc-NGA association constant KA as measured by Scatchard binding assay of the biopsied tissue. The correlation coefficients between in vivo and in vitro measurements were 0.73 (df = 8, p = 0.015) and 0.98 (df = 8, p less than 0.01) for Ro and kb, respectively. The in vivo measurements of HBP biochemistry via kinetic analysis of the radiopharmaceutical time-activity data reflect the average concentration and affinity of the receptor. This study further substantiates the validity of 99mTc-NGA as a quantitative probe for the HBP receptor.
Kudo
M
M
Department of Radiology, University of California, Davis, Sacramento 95817.
Vera
D R
DR
Trudeau
W L
WL
Stadalnik
R C
RC
D000328:Adult; D000368:Aged; D000418:Albumins; D037263:Asialoglycoprotein Receptor; D001706:Biopsy; D002352:Carrier Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology*; D008107:Liver Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D011877:Radionuclide Imaging; D011971:Receptors, Immunologic / Q000378:metabolism*
D000418:Albumins; D037263:Asialoglycoprotein Receptor; D002352:Carrier Proteins; D015609:Organotechnetium Compounds; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D011971:Receptors, Immunologic; C032193:glycoprotein receptor GPIb-IX; C027122:hepatic sialoglycoprotein receptor; C036586:technetium Tc 99m neogalactoalbumin