Parenchymal and nonparenchymal uptake of technetium-99m, indium-111, and iodine-125 low-density lipoprotein in the normal and estradiol-stimulated rat liver: Tracer validation for quantitative low-density lipoprotein scintigraphy
✍ Scribed by Thomas Leitha; Anton Staudenherz; Marcela Hermann; Manfred Hüttinger; Bernhard Gmeiner
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 875 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0270-9139
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✦ Synopsis
This study quantifies the parenchymal and nonparenchymal uptake of technetium-99m (-Tc)-and indium-111 (lllIn)-low-density lipoprotein (LDL) in different states of hepatic LDL-receptor activity to validate quantitative LDL scintigraphy. Iodine-125 ('=I)-LDL was used as reference tracer. Four Sprague-Dawley rats with 17alpha-ethinyl estradiol (EE)-stimulated LDL-receptor activity and five controls received all three tracers simultaneously 90 minutes before collagenase liver perfusion and metrizamide gradient cell separation. Total liver uptake of Y c -, l1'1n-, and 12'I-LDL was 1.8 f 1.0, 1.6 f 0.8, and 0.2 f 0.2% injected doselg organ weight, respectively. The contribution of nonparenchymal cells to total hepatic tracer uptake was 5.4 f 4.7%, 11.6 f 10.3%, and 9.6 2 7.6% in controls. Estradiol treatment increased total liver uptake to 2.4 -+ 0.5,2.0 f 0.2, and 0.5 f 0.3% injected dosdg and reduced nonparenchymal cell contribution to 2.3 f 2.6%, 4.2 f 4.8%, and 2.6 f 2.90/0, respectively. Dual-isotope scintigraphy in EE-treated and control rats confirmed these data, with a lower total hepatic uptake of 'llIn-LDL in comparison with Y c -LDL but a comparative degree of increase by EE treatment. Both behave quantitatively comparable as residualizing tracers, yet T c -L D L shows a higher affinity to the LDL receptor pathway of parenchymal cells. However, the nonspecific uptake of both tracers can be neglected for quantitative LDL scintigraphy, and external imaging of hepatic tracer uptake primarily reflects LDLreceptor activity of parenchymal cells. (HEPATOLOGY The integrity of the apoprotein BE-receptor pathway is a crucial factor for human low-density lipoprotein (LDL) metabolism. Quantitatively the liver is the major site of production and degradation of LDL.l Radioiodin-