Influence of 26-hydroxycholesterol on the composition and function of gel-filtered platelets.
The influence of 26-hydroxycholesterol (26-OH-CHOL) on the structure and function of gel-filtered rat platelets, as a model membrane, was studied in vitro. Its influence on structure was determined by a fatty acid and a phospholipid analysis of the platelet lipids and on function by the cytoplasmic calcium concentration of the platelets exposed to increasing concentrations of 26-OH-CHOL for various periods of time. The intracellular free calcium (Ca2+)i of the gel-filtered rat platelets was monitored by a fluorescent probe (quin 2) after incubation in a 37 degrees C water bath with 1 mM Ca2+ and 20 microM quin 2/AM. The presence of 26-OH-CHOL in the incubation media changed both the phospholipid composition and the mixed fatty acid composition in the membrane and increased the intracellular free Ca2+ level of the platelets. As the incubation of platelets with cholesterol (CHOL) or esterified 26-OH-CHOL did not increase intracellular Ca2+ levels, these results indicate that the hydrophilic free 26-hydroxy group in 26-OH-CHOL may have influenced the enzymes catalyzing the synthesis of the phospholipid in the platelet membrane so as to allow it to become more and more "leaky" to Ca2+. Such a fundamental change in membrane structure and function may be responsible for the development of atherosclerosis in the intimal layer of the coronary arteries.
Kou
I L
IL
School of Pharmacy, University of Southern California, Los Angeles.
Pikul
J
J
Kummerow
F A
FA
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D002850:Chromatography, Gel; D004952:Esters / Q000097:blood; D005227:Fatty Acids / Q000097:blood; D006888:Hydroxycholesterols / Q000097:blood*; D066298:In Vitro Techniques; D008297:Male; D008563:Membrane Lipids / Q000097:blood; D010743:Phospholipids / Q000097:blood; D010974:Platelet Aggregation; D051381:Rats; D013050:Spectrometry, Fluorescence; D014316:Tritium
D004952:Esters; D005227:Fatty Acids; D006888:Hydroxycholesterols; D008563:Membrane Lipids; D010743:Phospholipids; D014316:Tritium; C007042:cholest-5-ene-3 beta,26-diol; D002118:Calcium