A MODIFIED SODIUM DODECYL SULFATE-AGAROSE GEL IMMUNOBLOTTING METHOD FOR APOLIPOPROTEIN(A) PHENOTYPING USING ALKALINE PHOSPHATASE-LINKED CHEMILUMINESCENT DETECTION

Apolipoprotein(a) [apo(a)] is a highly polymorphic plasminogen-like gl ycoprotein and is the distinctive constituent of lipoprotein(a) [Lp(a) ]. The size heterogeneity of apo(a) is due to differences in the numbe r of kringle IV (K-IV) encoding repeats in the apo(a) gene and this is responsible for the size polymorphism in the expressed proteins (phen otypes).(1) Apo(a) genomic DNA size polymorphism has been demonstrated by using pulsed field gel electrophoresis (PFGE) followed by Southern blot hybridized with specific probes and this has shown that the numb er of K-IV repeats ranges between 12 and 51. We describe a simplified sodium dodecyl sulphate (SDS)-agarose gel electrophoresis (AGE) method for apo(a) phenotyping using alkaline phosphatase-linked chemilumines cent detection. Apo(a) isoforms were designated according to the numbe r of K-IV repeats.