Changes of the main isoform of human apolipoprotein A-I following incubation of plasma.
This study was aimed to ascertain whether the more acidic isoforms of plasma apo A-I (A-I-1 and A-I-2) could originate in vitro from the main plasma isoform (A-I0). Apo A-I isoforms were separated by two-dimensional gel electrophoresis before and after a prolonged incubation of serum or EDTA-plasma at 37 degrees C. Incubated plasma there was a marked decrease of apo A-I0 and a concomitant linear increase of apo A-I-1 + and A-I-2. The relative content of the latter raised from 22 +/- 7% before the incubation to 60 +/- 7% after 48 h of incubation. This conversion of A-I0 was not inhibited by either pre-heating of plasma at 60 degrees C for 1 h or the addition of protease inhibitors, EDTA and p-chloromercuriphenylsulfonic acid. The conversion of apo A-I0 was not observed in isolated HDL, incubated either in the absence or in the presence of d less than 1.063 g/ml lipoproteins and lipoprotein deficient plasma, nor in plasma which had been dialyzed before being incubated at 37 degrees C. This suggests that plasma contains a low molecular weight factor capable of promoting the conversion of A-I0. The increase of the relative content of apo A-I-1 and apo A-I-2 in incubated plasma was not due to glucosylation or carbamylation of A-I0 as no radioactive glucose and urea were found to be bound to A-I. Since the conversion of apo A-I0 was prevented by the addition of an antioxidant (butylated hydroxytoluene, BHT) to the incubated plasma it is conceivable that some product of lipid peroxidation renders apo A-I0 more electronegative by reacting with some free amino groups of this peptide.
Ghisellini
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M
Pecorari
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M
Calandra
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S
D000328:Adult; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000097:blood*; D001786:Blood Glucose / Q000378:metabolism; D002084:Butylated Hydroxytoluene / Q000494:pharmacology; D004492:Edetic Acid; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood; D053439:Lipoproteins, HDL2; D053440:Lipoproteins, HDL3; D008297:Male; D014508:Urea / Q000097:blood
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D001786:Blood Glucose; D008075:Lipoproteins, HDL; D053439:Lipoproteins, HDL2; D053440:Lipoproteins, HDL3; D002084:Butylated Hydroxytoluene; D014508:Urea; D004492:Edetic Acid