Inhibition of cation cotransport by cholesterol enrichment of human red cell membranes.
1. Human red cells were enriched with cholesterol by incubation with lipid dispersions having a high cholesterol: phospholipid mol ratio and the kinetics of the furosemide-sensitive cotransport for Na+ and K+ were measured. 2. Influxes of both K+ and Na+ through this system were inhibited by 70 and 76% in cholesterol-rich cells (cholesterol: phospholipid mol ratio 1.80) and the Km of the furosemide-sensitive flux components for both K+ and Na+ decreased. 3. Effluxes of both K+ and Na+ are inhibited by furosemide and the magnitudes of these furosemide-sensitive components are markedly decreased in cholesterol-rich cells. 4. The inhibitory effect of cholesterol enrichment on this carrier-mediated transport of cations suggests that cholesterol may either alter the position of the carrier or retard its movement within a more viscous membrane micro-environment.
D001693:Biological Transport, Active; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002784:Cholesterol / Q000494:pharmacology*; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D010743:Phospholipids / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D012964:Sodium / Q000097:blood*
D010743:Phospholipids; D010042:Ouabain; D005665:Furosemide; D002784:Cholesterol; D012964:Sodium; D011188:Potassium