Studies on the Fate of Normal and Variant Prealbumin in the Circulation
Owing to the recent studies on protein chemistry and genetic engineering, replacement of the val-30 residue of prealbumin by methionine, is believed to play a critical role in the formation of amyloid deposition and in the pathogenesis of familial amyloidotic polyneuropathy (FAP). However, only a limited information is available concerning the behavior of prealbumin in the circulation and the mechanism by which only the variant form protein results in amyloid deposition in certain tissues. Physiological importance and the fate of prealbumin synthesized by choroid plexus also remained obscure. To get the molecular insight into the mechanism of amyloid deposition, the fate of prealbumin from normal and FAP patient’s serum was studied in normal rats as well as in animals that were challenged with oxidative stress by acute inflammation. The in vivo fate of human prealbumin samples were also studied after injection into subarachnoid space in the rat. Kinetic analysis revealed that the plasma clearance of these prealbumin samples from normal rat and human subjects as well as from FAP patients were quite similar both in normal rats and in animals that were challenged with oxidative stress. The effect of photooxidation of prealbumin on its behavior was also examined in vivo. However, no appreciable difference was found between the two human prealbumin samples. These results suggest that other factor(s) than the conversion of the val-30 to methionine and the rate of transfer of prealbumin molecule from plasma to extravascular compartments may play a critical role in the pathogenesis of amyloid deposition in FAP patients.
KeywordsVariant Form Subarachnoid Space Amyloid Deposition Choroid Plexus Plasma Half Life
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