Studies on the mechanism of cholesterol uptake by the rat tapeworm Hymenolepis diminuta (Cestoda).
1. With increasing cholesterol content in mixed micelles, the rate of cholesterol uptake by the tapeworm approaches a limiting, maximal value. 2. This uptake is inhibited only 32-40% by other sterols, but is not markedly dependent on medium pH or tapeworm energy metabolism. 3. The competitive exchange diffusion of absorbed [14C]cholesterol could not be demonstrated. 4. The above results partially support the hypothesis that the tapeworm absorbs cholesterol by a specific carrier-mediated process. 5. Cholesterol uptake is reduced when the capacity of the micellar phase of the medium is increased, suggesting that uptake involves the intermediate partitioning of sterol from micelles into the aqueous phase of the medium.
Johnson
W J
WJ
Department of Biology, University of Iowa, Iowa City 52242.
Cain
G D
GD
D000042:Absorption; D000818:Animals; D001693:Biological Transport, Active; D002784:Cholesterol / Q000493:pharmacokinetics*; D004734:Energy Metabolism; D006863:Hydrogen-Ion Concentration; D006926:Hymenolepis / Q000378:metabolism*; D008823:Micelles; D008871:Microvilli / Q000378:metabolism; D013261:Sterols / Q000493:pharmacokinetics
D008823:Micelles; D013261:Sterols; D002784:Cholesterol