Quantitation of Ca2+ uptake by Arsenazo III-loaded liposomes.
Arsenazo III-loaded liposomes are in wide use as model systems in the study of Ca2+ transport. The most sophisticated method for quantitation of Ca2+ uptake [E. B. Smaal et al. (1985) Biochim. Biophys. Acta 816, 418] utilizes the absorbance changes (650-700 nm) elicited by sequential additions of EDTA and A23187 to distinguish Ca2+-Arsenazo complexes which are outside and inside the liposomes. In this paper, the analytical approach of Smaal and co-workers is reevaluated and a straightforward treatment that allows calculation both of the concentration of Ca2+ inside liposomes and of total Ca2+ uptake (in moles/mole phospholipid) is developed.
Sokolove
P M
PM
Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore 21201.
Kester
M B
MB
D001150:Arsenazo III; D001391:Azo Compounds; D002118:Calcium; D002308:Cardiolipins; D007700:Kinetics; D008081:Liposomes; D008962:Models, Theoretical; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D013053:Spectrophotometry / Q000379:methods
D001391:Azo Compounds; D002308:Cardiolipins; D008081:Liposomes; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D001150:Arsenazo III; D002118:Calcium