Bastien D. Gomperts

Quercetin: A novel inhibitors of Ca2+ influx and exocytosis in rat peritoneal mast cells

Abstract The effect of the transport ATPase inhibitor, quercetin on histamine secretion from antigen sensitized mast cells was examined. At micromolar concentrations, quercetin had an immediate inhibitory effect on histamine secretion mediated by antigen, concanavalin A and ATP but it had little effect on release induced by the ionophores A23187 and X537A. Quercetin exerts its effect after the binding of the releasing ligands and the distinction between its effect on ligand induced and A23187 induced secretion suggests that it affects the normal path of Ca2+ entry into the cell. The inhibitory effects of quercetin were compared with those of the structurally related anti-allergic drugs cromoglycate and AH7725.

Mobile carrier ionophores for Fe(II)

A23187 and certain other carboxylate ionophores are capable of transferring Fe(II) but not Fe(III) across phospholipid bilayers (liposomes) and red cell membranes. A23187 is able to transfer Fe(II) from ferritin loaded liposomes when allied with a suitable redox couple and sink. The affinity of A23187 for Fe(II) is approximately five orders of magnitude greater than for Ca2+, as judged by two phase extraction techniques.

The time cours of phosphorus incorporation in human red cells

Abstract 1. 1. The time course of phosphorus incorporation in red cell Pi, ADP, ATP and 2,3-diphosphoglycerate has been studied over the period from 10 to 20 min. 2. 2. It is shown that the terminal phosphorus atoms of ADP and ATP become labeled at a faster rate than intracellular Pi. 3. 3. The experiments suggest that the initial rate of 32Pi incorporation into the terminal phosphorus atom of ATP is the same as the initial rate of transfer of 32Pi from plasma to cells. 4. 4. It is shown that 2,3-diphosphoglycerate is synthesized at about one-ninth of the rate of ATP from their common precursor.

Molecular Events in Membrane Fusion Occurring During Mast Cell Degranulation

Mast cells provide an unusually attractive system for considering the molecular events involved in membrane fusion. When either antigen, (1) anti-immunoglobulin (Ig) antibody (2) or concanavalin A (con A) (3,11) bind to and cross link cytophilic IgE (9,11,13) on the surface of sensitized mast cells in the presence of extracellular Ca2+ (7), they induce exocytotic histamine release (degranulation) within seconds (l6). Degranulation involves the fusion of granule membranes with plasma membrane (and subsequently with other granules) followed by the opening of the granule contents to the extracellular space (3,12). Histamine contained in the granules is released by a process of cation exchange; histamine bound to granule matrix exchanges mainly with extra-cellular Na+ (16). Histamine release leads to easily recognisable ultra-structural changes in the granules, including loss of electron density and homogeneity, and an increase in size (3,4,12). Since the cells degranulate all over their surface there is always an extensive amount of membrane interaction and fusion taking place. They are, therefore, an excellent system in which to study the molecular events that occur during membrane fusion.