Formation of high density lipoproteins containing both apolipoprotein A-I and A-II in the rabbit.
Human plasma HDLs are classified on the basis of apolipoprotein composition into those that contain apolipoprotein A-I (apoA-I) without apoA-II [(A-I)HDL] and those containing apoA-I and apoA-II [(A-I/A-II)HDL]. ApoA-I enters the plasma as a component of discoidal particles, which are remodeled into spherical (A-I)HDL by LCAT. ApoA-II is secreted into the plasma either in the lipid-free form or as a component of discoidal high density lipoproteins containing apoA-II without apoA-I [(A-II)HDL]. As discoidal (A-II)HDL are poor substrates for LCAT, they are not converted into spherical (A-II)HDL. This study investigates the fate of apoA-II when it enters the plasma. Lipid-free apoA-II and apoA-II-containing discoidal reconstituted HDL [(A-II)rHDL] were injected intravenously into New Zealand White rabbits, a species that is deficient in apoA-II. In both cases, the apoA-II was rapidly and quantitatively incorporated into spherical (A-I)HDL to form spherical (A-I/A-II)HDL. These particles were comparable in size and composition to the (A-I/A-II)HDL in human plasma. Injection of lipid-free apoA-II and discoidal (A-II)rHDL was also accompanied by triglyceride enrichment of the endogenous (A-I)HDL and VLDL as well as the newly formed (A-I/A-II)HDL. We conclude that, irrespective of the form in which apoA-II enters the plasma, it is rapidly incorporated into spherical HDLs that also contain apoA-I to form (A-I/A-II)HDL.
Hime
Neil J
NJ
Lipid Research Group, The Heart Research Institute, Camperdown, Sydney, New South Wales 2050, Australia.
Drew
Kate J
KJ
Wee
Kevin
K
Barter
Philip J
PJ
Rye
Kerry-Anne
KA
D000818:Animals; D016632:Apolipoprotein A-I / Q000097:blood*; D016633:Apolipoprotein A-II / Q000008:administration & dosage / Q000097:blood*; D006801:Humans; D007275:Injections, Intravenous; D008055:Lipids / Q000097:blood; D008075:Lipoproteins, HDL / Q000008:administration & dosage / Q000097:blood* / Q000737:chemistry*; D008297:Male; D011817:Rabbits; D014280:Triglycerides / Q000097:blood
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D008055:Lipids; D008075:Lipoproteins, HDL; D014280:Triglycerides