Determination of fractional disappearance rate of kidney cholesterol

¹ Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky

Mevalonic acid-2-C¹⁴ was injected intraperitoneally into rats, and the incorporation of the C¹⁴ into cholesterol of various tissues determined. A disproportionate incorporation into kidney cholesterol was observed, resulting in a specific activity 55 times that of serum cholesterol with which it can exchange. This selective labeling of kidney cholesterol and the essentially identical cholesterol-C¹⁴ content found in the two kidneys permitted the determination of the disappearance rate constant of kidney cholesterol without the necessity of considering back exchange of the label. One week after the intraperitoneal injection of mevalonic acid-2-C¹⁴ into an additional group of rats the left kidney was removed from each animal and its cholesterol-C¹⁴ content determined; from 2 to 6 weeks later the remaining kidney was removed and its cholesterol-C¹⁴ content also determined. A disappearance rate constant of the labeled kidney cholesterol of 0.030 day^–1 was found.