ENDOCYTOSIS, CA2 AND MEMBRANE DEFECTS IN SICKLE CELLS

镰状细胞含有小的内吞囊泡，其中含有钙离子

Sickle cells contain small endocytic vesicles within which Ca++ is concentrated. Fluorescence assays which detect either the presence or the formation of these vesicles will be used to screen patient populations to determine whether vesicles are germane to the clinical course of the disease. Fick cytometry and fluorescence microscopy will be used to determine the characteristics and mechanism of vesicle formation, with particular attention to the question of the relationship between the endocytosis which produces these vesicles in sickle cells and classical receptor mediated endocytosis as it occurs in normal reticulocytes. Fluorescence assays will also be used to determine the conditions under which vesicle lysis and Ca++ release occurs. The characteristics of the Ca++ pulse which occurs when vesicles lyse will be measured. Using a variety of assays, several Ca++ sensitive red cell membrane characteristics, such as lipid asymmetry, adhesion, and ability to activate the coagulation mechanism, will be restudied to determine whether they are preferentially altered in cells in which vesicles occur, whether their sensitivity to Ca++ is such that they could be effected by a Ca++ pulse, and whether their sensitivity to Ca++ is enhanced in sickle cells.