A comparison of the low-density-lipoprotein receptor from bovine adrenal cortex, rabbit and rat liver and adrenal glands by lipoprotein blotting

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Abstract
This paper describes the use of lipoprotein blotting to detect low-density-lipoprotein (LDL) receptors in rat and rabbit liver and adrenal glands and in bovine adrenal glands. Using this technique we show that the rabbit and rat liver LDL receptors have Mr values of 128000 and 145000 respectively. Mr values for the rabbit, rat and bovine adrenal receptors are 131000, 142000 and 132000 respectively. Differences between the bovine adrenal and rat liver receptors are not due to differences in the degree of sialylation. Lipoprotein blotting can be used to detect dietary- and drug-induced changes in the concentrations of LDL receptors. When rabbits are fed on a cholesterol-rich diet, liver LDL receptors cannot be detected, consistent with the suppression of hepatic LDL receptors by cholesterol feeding. Pharmacological doses of 17 alpha-ethinyloestradiol cause a marked increase in hepatic LDL-receptor activity in the rat. This is accompanied by a corresponding increase in the number of LDL receptors detected by lipoprotein blotting. The Mr of the induced receptor is identical with that of the receptor from control rats, which suggests that the induced receptors are produced by the same gene as LDL receptors normally present in the liver.