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Metal Selectivity of Exocytosis in α-Toxin-Permeabilized Bovine Chromaffin Cells (1996)

Tomsig, J. L. ; Suszkiw, J. B.

Oxford, UK : Blackwell Science Ltd

Journal of neurochemistry 66 (1996), S. 0

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ISSN: 1471-4159

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Medicine

Notes: Abstract: Metal selectivity of exocytosis was analyzed by comparing the effects of polyvalent metal cations Ca2+, Ba2+, Sr2+, Pb2+, La3+, Cd2+, Co2+, Tb3+, Mn2+, and Zn2+ on the release of norepinephrine (NE) from staphylococcal α-toxin-permeabilized bovine chromaffin cells. Pb2+, La3+, Cd2+, Sr2+, and Ba2+ activated NE secretion accompanied by the release of intragranular dopamine β-hydroxylase but not cytosolic lactate dehydrogenase, indicating the activation of the mechanism of exocytosis. The release triggered by saturating concentrations of Pb2+, La3+, Cd2+, and Sr2+ was nonadditive with Ca2+, indicating a common site of action. In contrast, the Ba2+-evoked NE release was additive with Ca2+ and the Ca2+ agonists Pb2+, La3+, Cd2+, and Sr2+, suggesting that Ba2+ activates secretion at a site distinct from the Ca2+ receptor. In distinction to the NE release evoked by Pb2+, La3+, Cd2+, and Ba2+, the Sr2+-evoked NE release was associated with a significant elevation of Ca2+ concentration in the medium and abolished by Ca2+ chelation. This indicates that the secretagogue effect of Sr2+ was indirect and secondary to the displacement of bound Ca2+. Co2+ and Mn2+ inhibited the NE release evoked by Ca2+, Sr2+, Pb2+, La3+, and Cd2+ but had no effect on the Ba2+-dependent secretion. Tb3+ and Zn2+ were without effect on exocytosis.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1471-4159.1996.66020644.x

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Effect of collidine (2,4,6-trimethylpyridine) on the osmiophilia and chromaffin reaction in the synaptic vesicles of rat pineal nerves (1987)

Tomsig, J. L. ; Pellegrino de Iraldi, A.

Springer

Histochemistry and cell biology 87 (1987), S. 21-25

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ISSN: 1432-119X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary Rat pineal nerve endings contain a population of small and of large synaptic vesicles that are either electron lucent or have electron-dense cores. It has been reported that their osmiophilia is elminated when collidine buffer is used in the fixation procedure. We investigated this effect and found that osmium tetroxide and potassium dichromate reactivity were abolished when excised pineal glands were briefly incubated with collidine buffer before glutaraldehyde-cacodylate fixation. Such an effect was not observed when collidine was applied after fixation. Glands that had been fixed in glutaraldehyde or osmium tetroxide buffered with collidine exhibited a peripheral zone containing reactive synaptic vesicles and a deeper, central zone where such reactivity was absent. These results indicate that the effect of collidine is due to depletion of monoamines rather than to chemical blockage of their reactivity, and further suggest that collidine has a higher rate of penetration into tissues than the tested fixatives.