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Molecular level investigation of exocytosis in cultured human pheochromocytoma cells: insights from high resolution scanning electron microscopy combined with autoradiogram and cytochemistry.

Abstract：

OBJECTIVE:To investigate molecular events of exocytosis in cultured human pheochromocytoma cells with stimulation. METHODS:The cultured pheochromocytoma cells prepared from human adrenal pheochromocytoma tumor were stimulated for the release of catecholamines by depolarization with the administration of 50 mmol/L KCl. Transmission electron microscopy (TEM) and high resolution scanning electron microscopy (HR-SEM) combined with autoradiography and cytochemistry were used to observe molecular mechanisms of exocytotic release of catecholamines from the stimulated cells labelled with 3H-noradrenaline and the filipin-treated cells. RESULTS:TEM and HR-SEM observations of the stimulated cells labelled with 3H-noradrenaline revealed that the initial exocytotic fusion pores even less than 10 nm in diameter in human pheochromocytoma cells can be clearly observed in a single lipid bilayer. Furthermore, HR-SEM examinations of the filipin-treated cells showed that the derangement of the particles of the filipin-sterol complexes (FSCs) in the fused membranes of granule and plasma membranes occurred as the exocytotic fusion pores opened. In addition, the aggreates of the FSCs particles were consistently demonstrated around the openings of the differently sized closing exocytotic pores. CONCLUSIONS:Based on our results, it is suggested that the rearrangement of the sterol molecules in the fused membranes of granule and plasma membranes plays an important role in the opening and closing mechanisms of exocytotic fusion pores. We hope that morphological data obtained in this study can provide some new insights into the understanding of molecular mechanisms of exocytosis, particularly the opening and closing of exocytotic fusion pores in relation to the distribution of the membrane sterols.

journal_name

Chin Med J (Engl)

journal_title

Chinese medical journal

authors

Lee YS,Chou YY

keywords:

subject

Has Abstract

pub_date

1998-04-01 00:00:00

pages

295-301

issue

eissn

0366-6999

issn

2542-5641

journal_volume

111

pub_type

杂志文章

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Molecular level investigation of exocytosis in cultured human pheochromocytoma cells: insights from high resolution scanning electron microscopy combined with autoradiogram and cytochemistry.