Fate of intravenously administered high-density lipoprotein labeled with radioiodinated cholesteryl oleate in normal and hypolipidemic rats.

Radioiodinated cholesteryl oleate (125I-CO) was found to associate rapidly with plasma lipoproteins following intravenous administration to rats. The high-density lipoprotein (HDL) fraction was observed to contain the highest amount of radioiodinated ester. Isolation and purification of this HDL fraction (125I-CO-HDL) and subsequent administration to rats demonstrated a plasma clearance similar to that previously observed for HDL labeled by direct iodination. Moreover, the concentration of radioactivity appearing in the adrenal cortex and ovary 0.5 h after intravenous administration of 125I-CO-HDL was greater than that observed after administration of 125I-CO, and the uptake of radioactivity by these tissues was considerably greater in hypolipidemic rats. These findings are consistent with existing knowledge relating to the metabolic fate of HDL and radioiodinated cholesterol derivatives in the rat, and suggest that radioiodinated cholesteryl esters may become useful probes for labeling lipoproteins.