ARTERIAL FATTY LESIONS HAVE INCREASED UPTAKE OF CHYLOMICRON REMNANTS BUT NOT LOW-DENSITY LIPOPROTEINS

Background This study compares the accumulation of pre-formed chylomic ron-remnants, chylomicrons and low-density lipoproteins (LDL) in rabbi t thoracic aorta, To determine whether lipoproteins are delivered via the vasa vasorum, the aortic uptake of lipoproteins was compared to th at of the common carotid artery, The uptake of chylomicron remnants an d LDL were compared in lesioned and non-lesioned aortic tissue from Wa tanabe heritable hyperlipidaemic (WHHL) rabbits.Methods Chylomicrons, chylomicron-remnants and LDL were radio-labelled with tyramine-cellobi ose and injected into rabbits, Arterial uptake was determined after 2 h as the percentage of injected lipoproteins associated with arterial tissue and also expressed as a fraction of mean arterial exposure. Res ults Aortic accumulation of radio-labelled chylomicron-remnants was su bstantially greater than for chylomicrons, and both were significantly greater than LDL, The data suggests that chylomicrons must first be h ydrolysed to smaller particles before uptake, In normal rabbits, there was no difference in uptake of the lipoproteins between the aorta and carotid vessels, suggesting that the vasa vasorum is not significantl y involved in lipoprotein delivery, However, in WHHL rabbits there was significantly greater aortic uptake of chylomicrons and LDL compared to the carotid vessel and, in cholesterol-fed rabbits, significantly g reater aortic uptake of chylomicrons, suggesting that in hypercholeste rolaemia the lipoprotein retention properties of some arterial beds ch ange, In arterial fatty lesions from WHHL and cholesterol-fed rabbits there was an exclusive increase in chylomicron remnant uptake, whereas LDL uptake was similar to non-lesioned tissue. Conclusions Chylomicro n remnants and not their precursors might be primary atherogenic lipop rotein because they penetrate arterial tissue efficiently and are sele ctively retained in sites of lesion formation.