title: Studies on the source of urinary cholesterol in the normal human male.
abstract: The aim of the present study was to obtain information on the source of urinary cholesterol in normal men of various age groups (22-25, 37-42, greater than 63 yrs). Aliquots of 24-hr urine samples were fractionated by ultracentrifugation. Between 10-20% of the total cholesterol in urine (measured by gas-liquid chromatography) separately sedimented after 2 x 10(4) g-min and after 4 x 10(5) g-min of centrifugation. However, an average of more than 50% of the total sedimented after 6 x 10(6) g-min and only 10-20% of total cholesterol remained in this supernatant. These results indicate that most of the cholesterol in urine of normal males is a component of a light particulate fraction. Little difference was seen in the distribution of urinary cholesterol among the various age groups examined The 4 x 10(5) g-min supernatant from 24-hour total urine samples was recentrifuged at 10(5) g for 60 min. The resulting pellet (100 P) was assayed for protein, total cholesterol and phospholipid. The cholesterol was 12-14% esterified. A molar ratio of total cholesterol to phospholipid of 1 to 0.8 was calculated. Assay of the 100 P fraction for marker enzymes showed an activity pattern characteristic for plasma membranes. Fractionation of the 100 P proteins by electrophoresis and separation of the 100 P phospholipids by thin-layer chromatography revealed patterns clearly different from those of human red cell plasma membrane. Electron micrographs of the 100 P fraction revealed an appearance similar to that of deteriorated membranes. The results suggest that most of the cholesterol in urine of the adult human male is present as a component of membranes derived from endogenous cells of the urogenital system.
mesh_terms: D000328:Adult; D000368:Aged; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000032:analysis / Q000652:urine*; D002788:Cholesterol Esters / Q000652:urine; D006801:Humans; D008297:Male; D008875:Middle Aged; D010743:Phospholipids / Q000032:analysis; D011506:Proteins / Q000032:analysis; D012016:Reference Values; D014461:Ultracentrifugation
chemical_list: D002788:Cholesterol Esters; D010743:Phospholipids; D011506:Proteins; D002784:Cholesterol