Influence of membrane physical state on lysosomal potassium ion permeability.
Lysosomal permeability to potassium ions is an important property of the organelle. Influence of the membrane physical state on the potassium ion permeability of isolated lysosomes was assessed by measuring the membrane potential with bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol and monitoring the lysosomal proton leakage with p-nitrophenol. The membrane fluidity of lysosomes was modulated by treatment with membrane fluidizer benzyl alcohol and rigidifier cholesteryl hemisuccinate. Changes in the membrane order were examined by steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene. The measurements of membrane potential and proton leakage demonstrated that the permeability of lysosomes to potassium ions increased with rigidification of their membranes by cholesteryl hemisuccinate treatment at 37 degrees C, and decreased with fluidization of their membranes by benzyl alcohol treatment at 2 degrees C. The changes in ion permeability could be recovered by fluidizing the rigidified membranes and rigidifying the fluidized membranes. The results suggest that the physical states of lysosomal membranes play an important role in the regulation of their K(+) permeability.
Wang
Jun
J
Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, PR China.
Zhang
Guo-Jiang
GJ
D000818:Animals; D019905:Benzyl Alcohol / Q000494:pharmacology; D002788:Cholesterol Esters / Q000494:pharmacology; D005454:Fluorescence Polarization; D007425:Intracellular Membranes / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials; D010539:Permeability; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014634:Valinomycin / Q000494:pharmacology
D002788:Cholesterol Esters; D014634:Valinomycin; D019905:Benzyl Alcohol; D011188:Potassium; C013440:cholesteryl succinate