The permeability of the lysosomal membrane to small ions.
The permeability of the lysosomal membrane to small anions and cations was studied at 37 degrees C and pH 7.0 in a lysosomal-mitochondrial fraction isolated from the liver of untreated rats. The extent of osmotic lysis following ion influx was used as a measure of ion permeancy. In order to preserve electroneutrality, anion influx was coupled to an influx of K+ in the presence of valinomycin, and cation influx was coupled to an efflux of H+ using the protonophore 3-tert-butyl-5,2'-dichloro-4'-nitrosalicilylanilide. Lysosomal lysis was monitored by observing the loss of latency of two lysosomal hydrolases. The order of permeability of the lysosomal membrane to anions was found to be SCN- greater than I- greater than CH3COO- greater than Cl- approximately Pi greater than SO24- and that to cations Cs+ greater than K+ greater than Na+ greater than H+. These orders are largely in agreement with the lyotropic series of anions and cations. The implications of these findings for the mechanism by means of which a low intralysosomal pH is produced and maintained are discussed.
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D000838:Anions; D001692:Biological Transport; D002414:Cations, Monovalent; D006596:Hexosaminidases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008566:Membranes / Q000378:metabolism*; D051381:Rats; D013329:Structure-Activity Relationship; D014634:Valinomycin / Q000494:pharmacology
D000838:Anions; D002414:Cations, Monovalent; D014634:Valinomycin; D000135:Acid Phosphatase; D006596:Hexosaminidases