Thin-layer chromatography of polyphosphoinositides from platelet extracts: interference by an unknown phospholipid.
Different ratios of radioactive polyphosphoinositides in platelets pulse-labelled with 32p-orthophosphate have been reported by various laboratories. We studied whether these differences originate from differences in methodology. Extracts of 32p-Pi labelled human platelets were prepared at various times after gel-filtration and phosphatidylinositol (PI)-, mono (PIP)- and bisphosphate (PIP2) were separated by thin-layer chromatography using four different solvent systems. The 32p-levels in PIP and PIP2 remained constant during one hour after gel-filtration, whereas 32p-PI increased continuously and more than doubled within the first h. In two of the systems PIP co-chromatographed with a radioactive compound which separated well from PIP in the two other systems. This unknown compound was also labelled with 3H-glycerol, 3H-inositol and 3H-arachidonic acid, but it was metabolically and functionally different from the polyphosphoinositides. Both the co-chromatography of this unknown phospholipid and the increase in 32p-PI in gel-filtered platelets can explain the difference in 32p-labelling in phosphoinositides reported in the literature.
D001792:Blood Platelets / Q000032:analysis*; D002855:Chromatography, Thin Layer / Q000379:methods; D006801:Humans; D007700:Kinetics; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000097:blood* / Q000302:isolation & purification; D010743:Phospholipids / Q000097:blood*; D010761:Phosphorus Radioisotopes; D011865:Radioisotope Dilution Technique; D012016:Reference Values; D012997:Solvents
D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010743:Phospholipids; D010761:Phosphorus Radioisotopes; D012997:Solvents