MODELING OF FLUID-PHASE ENDOCYTOSIS KINETICS IN THE AMEBAS OF THE CELLULAR SLIME-MOLD DICTYOSTELIUM-DISCOIDEUM - A MULTICOMPARTMENTAL APPROACH

Fluid-phase endocytosis (pinocytosis) kinetics were studied in Dictyos telium discoideum amoebae from the axenic strain Ax-2 that exhibits hi gh rates of fluid-phase endocytosis when cultured in liquid nutrient m edia. Fluorescein-labelled dextran (FITC-dextran) was used as a marker in continuous uptake- and in pulse-chase exocytosis experiments. In t he latter case, efflux of the marker was monitored on cells loaded for short periods of time and resuspended in marker-free medium. A multic ompartmental model was developed which describes satisfactorily fluid- phase endocytosis kinetics. In particular, it accounts correctly for t he extended latency period before exocytosis in pulse-chase experiment s and it suggests the existence of some sorts of maturation stages in the pathway.