The chromaffin granule proton pump and calcium-dependent exocytosis in bovine adrenal medullary cells
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Calcium-dependent exocytosis in ‘leaky’ bovine adrenal medullary cells has a requirement for Mg-ATP. One possibility is that exocytosis depends in some way on the operation of the ATP-dependent proton pump that serves to maintain the core of the secretory vesicles both acid and at a positive potential with respect to the cytosol. This possibility has been tested in ‘leaky’ cells by monitoring exocytosis under conditions where the secretory vesicle pH and potential gradients are measuredin situ. The results show rather clearly that exocytosis can persist, with unchanged Ca-activation kinetics, in the virtual absence both of a difference in pH between the cytosol and secretory vesicle core and also of a difference in potential across the vesicle membrane. The results do not, however, exclude a small modulating effect of vesicle pH or potential on exocytosis and shed no light on whether or not the plasma membrane potential, which is maintained close to zero in these experiments, influences exocytosis.
Key WordsExocytosis proton pump calcium secretion adrenal medulla
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- Baker, P.F., Knight, D.E. 1978a. A high voltage technique for gaining rapid access to the interior of secretory cells.J. Physiol. (London) 284:30P Google Scholar
- Baker, P.F., Knight, D.E. 1978b. Calcium-dependent exocytosis in bovine adrenal medullary cells with leaky plasma membranes.Nature (London) 276:620–622Google Scholar
- Baker, P.F., Knight, D.E. 1981. Calcium control of exocytosis and endocytosis in bovine adrenal medullary cells.Phil. Trans. R. Soc. London B 296:83–103Google Scholar
- Baker, P.F., Knight, D.E. 1982. Is the chromaffin granule membrane potential essential for Ca-dependent exocytosis?J. Physiol. (London) 326:10P Google Scholar
- Knight, D.E., Baker, P.F. 1982. Calcium-dependence of catecholamine release from bovine adrenal medullary cells after exposure to intense electric fields.J. Membrane Biol. 68:107–140Google Scholar
- Mahler, H.R., Cordes, E.H. 1971. Biological Chemistry. (2nd ed.) p. 13. Harper & Row, LondonGoogle Scholar
- Rubin, R.P. 1970. The role of energy metabolism in calcium evoked secretion from the adrenal medulla.J. Physiol. (London) 206:181–192Google Scholar
- Winkler, H., Carmichael, S.W. 1982. The chromaffin granule.In: The Secretory Granule. A.M. Poisner and J.M. Trifaro, editors. pp. 3–79. Elsevier, AmsterdamGoogle Scholar