Uptake of cholesterol esters being a part of the different fractions of blood plasma lipoproteins by rats organs and tissues

The paper deals with the functions of the main classes of blood plasma lipoproteins (LP) that are associated with the transport of cholesterol esters included in their composition. The aim of the study was to investigate the features of the uptake of cholesterol esters associated with plasma LP fractions (very low (VLDL), low (LDL), and high density LPs (HDL)) by rat organs and tissues, and to show the participation of various subfractions of HDL (HDL₂ and HDL₃) as specific cholesterol carriers in the main steroid-producing organs of rats.

Material and methods. The in vivo studies with intravenous LP injection of ¹⁴C labeled cholesterol oleate (¹⁴C-OCh) associated with plasma LP fractions have been carried out.

Results. Intravenous injection of a ¹⁴C-OCh) in the composition with VLDL led to the maximal mark uptake by the liver. Three times less uptake of labeled cholesterol was observed in the adrenal glands, testes and heart muscle. In other tissues radioactivity gradually decreased in the raw: spleen > lungs > kidneys > thyroid gland and adipose tissue. After the injection of ¹⁴C-OCh in the composition of LDL marked predominant uptake of the label by the adrenal glands, testes, and liver. A feature of the use of HDL as a carrier platform for ¹⁴C-OCh is the high accumulation of label in steroid-producing organs: the adrenal glands and testis. The dynamics of uptake of ¹⁴C-OCh in the composition of HDL by the adrenal glands and testes of rats in different time intervals after injection (30 min, 3, 6 and 12 h) was studied. Adrenal cells actively uptake ¹⁴C-OCh from HDL, as a result of which the radioactivity of the tissue increased rapidly and after 30 minutes almost reached its maximum. In contrast to the adrenal glands uptake of the testis was characterized by a gradual increase in radioactivity with a maximum of 6 hours and a rather sharp decrease to 12 hours from the beginning of the experiment. In vitro experiments showed the differences in the effect of HDL₂ and HDL₃ on the corticosterone production by the adrenal glands of rats.

Conclusions. The paper presents the features of uptake of cholesterol esters by organs and tissues of rats depending on the used LP-transporter (VLDL, LDL, HDL). In addition, the results suggest that HDL₃ subfraction may be the more preferred source of cholesterol for steroid synthesis in the adrenal cortex of rats compared to HDL₂ subfraction.

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