Hydrocarbon transport in chylomicrons and high‐density lipoproteins in rat

Abstract

A lipoprotein system is described that transports gut hydrocarbons of low polarity in chylomicrons of intestinal lymph and plasma to plasma high density lipoproteins (HDL) in rat. Four highly lipophilic aryl and alkyl hydrocarbons [benzo(alpha)pyrene; 1,1,1-trichloro-2,2-bis(p-chlorophenol)ethane (DDT), hexadecane and octadecane] were selected to give a graded range of polarity. Chylomicrons were labeled doubly with radioisotopes in triacylglycerol and a single hydrocarbon by feeding [3H]-glycerol and [14C]hydrocarbon. All hydrocarbons were transported in the triacylglycerol oil phase of chylomicrons. Injected chylomicron triacylglycerol and 3 of 4 hydrocarbons were cleared simultaneously from plasma consistent with lipoprotein-lipase dependent hydrocarbon clearance but DDT was cleared more rapidly. HDL was the major plasma acceptor of all labelled hydrocarbons. Plasma chemical fluxes were measured for octadecane and DDT and both showed net fluxes from chylomicrons to HDL. HDL selectively concentrated chylomicron hydrocarbons from chylomicron triacylglycerol. Lipoprotein lipase stimulation by intravenous heparin significantly increased transfer of alkanes from chylomicrons to HDL. These results indicate that (a) chylomicrons transport gut-derived hydrocarbons with a wide range of structure and polarity as triacylglycerol solutes; (b) HDL are a major plasma acceptor of all these hydrocarbons, demonstrating both selective solute uptake from triacylglycerol and net chemical uptake for the 2 hydrocarbons studied and (c) efflux of these chylomicron hydrocarbons from plasma and into HDL is regulated partly by hydrolysis of chylomicron triacylglycerol.

Distribution of toxaphene, DDT, and PCB among lipoprotein fractions in rat and human plasma

“…A similar overall distribution pattern was seen with 14C-PCB and 14C-DDT. The values obtained for the distribution of DDT in the fractions of rat plasma in vitro correspond to those found in earlier studies (Pocock and Vost 1974;Skalsky and Guthire 1975;Vost and Maclean 1984). On the other hand, 2,2', 4,4', 5,5'-hexachlorobiphenyl (6-[14C]CB), one of the PCB isomers, showed a relatively homogenous distribution among the various lipoprotein fractions in the plasma of rat (Vomachka et al 1983).…”

“…This is in contrast to the results of Vomachka et al (1984), who observed a major part of the intravenously injected 6-[ 14C]CB in association with the LDL fraction in rats in vivo. On the other hand, Pocock and Vost (1974) and Vost and Maclean (1984) reported that after peroral application of 14C-DDT to rats, the substance was transported via lymphatic chylomicrons to the plasma, and then transferred selectively from chylomicrons to HDL as well as to protein fractions in plasma. This indicates that the binding of persistent environmental pollutants to plasma fractions may differ significantly depending on the type of substance, dose, way of administration and the animal species used (see e.g.…”

“…Pocock and Vost 1974;Vomachka et at. 1984;Vost and Maclean 1984;Busbee et al 1985;Poland and Counsell 1985).…”

Vaccination-Induced Systemic Autoimmunity in Farmed Atlantic Salmon

“…Massive cytokine production induced by vaccination can also damage endothelial cells. Because adjuvant hydrocarbon oils are known to be incorporated into lipoproteins (40), these abnormal lipoproteins may play a direct or indirect role in endothelial cell damage, leading to thrombosis. The mechanism of autoimmunity in salmon may be consistent with the concept of innate autoimmunity (41).…”

Adipose tissue accumulation of endocrine disrupting compounds: Variant of a common theme in exposome research

“…As an example, PCB and organochlorine pesticides in blood are associated with the protein fraction, but also with lipoproteins (20). Although their binding with lipoproteins is considered as the major mechanism responsible for their accumulation, it may also be partially responsible for their lipotoxicity (21).…”