Triggered exocytosis and endocytosis have different requirements for calcium and nucleotides in permeabilized bovine chromaffin cells. 1993

H von Grafenstein, and D E Knight
Biomedical Sciences Division, Kings College London.

The intracellular requirements for membrane recapture in permeabilized chromaffin cells were compared to the requirements for exocytosis from the same cells. In permeabilized bovine chromaffin cells, calcium-driven exocytosis also triggers, with a short delay, uptake of extracellular horseradish peroxidase (HRP). This internalized HRP remains compartmentalized within the cell and migrates to a low density band on a Percoll gradient which is distinct from the heavier chromaffin granules. The amount of horseradish peroxidase internalized is similar in intact and leaky cells and is approximately equivalent to the volumes secreted. Endocytosis in both preparations is blocked by botulinum toxin, operates in a collapsed membrane potential, and is inhibited by low temperature. In permeabilized cells, exocytosis and coupled endocytosis are activated by the same concentrations of Ca2+ and MgATP. Although secretion requires Ca2+ and MgATP, once exocytosis has occurred the subsequent endocytosis can proceed in the virtual absence of Ca2+ or MgATP, and is largely unaffected by a variety of nucleotide triphosphates (including nonhydrolyzable analogues), and cyclic nucleotides. These data suggest that endocytosis can proceed, once exocytosis has been triggered, under conditions that are quite different from those necessary to support exocytosis, and that the specific requirements for Ca2+ and MgATP in secretion are for the exocytotic limb of the secretory cycle rather than for the associated endocytotic pathway.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002417 Cattle Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor. Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D002463 Cell Membrane Permeability A quality of cell membranes which permits the passage of solvents and solutes into and out of cells. Permeability, Cell Membrane
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D002838 Chromaffin System The cells of the body which stain with chromium salts. They occur along the sympathetic nerves, in the adrenal gland, and in various other organs. Argentaffin System,Argentaffin Systems,Chromaffin Systems,System, Argentaffin,System, Chromaffin,Systems, Argentaffin,Systems, Chromaffin
D003594 Cytoplasmic Granules Condensed areas of cellular material that may be bounded by a membrane. Cytoplasmic Granule,Granule, Cytoplasmic,Granules, Cytoplasmic
D004299 Dopamine beta-Hydroxylase Dopamine beta-Monooxygenase,Dopamine beta Hydroxylase,Dopamine beta Monooxygenase,beta-Hydroxylase, Dopamine,beta-Monooxygenase, Dopamine
D004705 Endocytosis Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis. Endocytoses
D005089 Exocytosis Cellular release of material within membrane-limited vesicles by fusion of the vesicles with the CELL MEMBRANE.

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