Lysosomal bis (monoacylglycero)phosphate of rat liver, its induction by chloroquine and its structure

Since chloroquine is able to induce phospholipidosis, and in particular formation of bis(monoacylglycero)phosphate [(MAG)2P] in rat liver lysosomes, we tested the influence of the drug on this acidic phospholipid 1) after application of the drug for different periods, 3, 7, 14, 21 and 28 days, and 2) after application of different doses of the drug for 7 days. In both cases, the amounts of the total phospholipids and of (MAG)2P within the lysosomal lipids showed a direct relationship to the quantity of the drug. Lysosomal fractions were identified by acid phosphatase activity and by electron microscopy. After 14 days of treatment, the lysosomal fractions showed an increase in the marker enzyme to more than 30 times the level in the homogenate, and consisted of almost pure "lamellar bodies". (MAG)2P was isolated from those lysosomal lipid fractions by column chromatography. We also isolated this phospholipid from "tritosomal" lipids and tested the two preparations in different ways. They both showed glycerophosphoglycerol as the only P-containing product after mild alkaline hydrolysis, and molar ratios for phosphorus: fatty acid: glycerol close to 1:2:2; and yielded diacetylacyl glycerol after acetolysis. Thus, there is no doubt that (MAG)2P occurs in these secondary lysosomes--as we described in others--and that its production is a consequence of accumulation of lysosomes. There is some indication for the occurrence of an acylated (MAG)2P (which is the same as acylphosphatidylglycerol) within the same cell organelles.