Visualization of the hepatic low-density lipoprotein receptor in rats by sequential scintiscans

The usefulness of a gamma camera system for external imaging of the degradation sites of low-density lipoprotein (LDL) is demonstrated in rats. [131I]LDL was injected intravenously in normal rats and rats pretreated with 17 alpha-ethinyl estradiol for LDL receptor induction. Distribution of the radioligand was followed for 20 min, for perfusion control [131I]albumin was administered. Rats pretreated with 17 alpha-ethinyl estradiol showed a marked increase in the LDL uptake by the liver, which was not competed by the preinjection of physiological amounts of unlabelled LDL. It is concluded that the injection of small amounts of [131I]LDL is sufficient to image the hepatic LDL receptor and that the endogenous LDL does not compete effectively at physiological LDL levels.