Lipoprotein incorporation enhances radioiodinated cholesteryl ester uptake into steroid hormone-secreting tissues

This study was undertaken to determine whether incorporation of radioiodinated cholesterol derivatives into plasma lipoproteins prior to administration to animals could lead to improvements in adrenal localization of radioactivity. Rat high density lipoproteins (HDL) were labeled with [125I]cholesteryl iopanoate, a nonhydrolyzable ester of cholesterol. No enhancement in adrenal uptake of radioactivity was noted at 30 min following administration of the HDL preparation to control rats when compared with [125I]NP-59. However, when animals were made hypolipidemic by treatment with either 4-APP or ethinyl estradiol, the adrenal radioactivity after i.v. administration of the HDL preparation was found to be over 15 times greater than that achieved with [125I]NP-59. Scans of hypolipidemic rats taken at 30 min correlated well with the tissue distribution results.