Monensin and hypo-osmolar medium cause calcium-independent β-endorphin secretion from melanotropes

被引:7
作者
Bäck, N
Soinila, S
Törnquist, K
机构
[1] Univ Helsinki, Dept Anat, Inst Biomed, FIN-00014 Helsinki, Finland
[2] Univ Helsinki, Dept Neurol, FIN-00014 Helsinki, Finland
[3] Univ Helsinki, Minerva Fdn Inst, FIN-00014 Helsinki, Finland
[4] Abo Akad Univ, Dept Biol, SF-20500 Turku, Finland
关键词
exocytosis; monensin; beta-endorphin; calcium; melanotropes; osmolarity;
D O I
10.1159/000054526
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
Monensin has been shown to cause nonexocytotic release of catecholamines from adrenal medullary and PC12 cells. We examined the effect of monensin on peptide secretion with cultured melanotropes from the rat pituitary as a model. 1 mu M monensin caused an immediate, transient increase in beta-endorphin secretion. The effect was still seen in a calcium-free medium, but was totally abolished in a sodium-free medium. Intracellular calcium concentration was measured with Fura 2: no increase was observed during monensin stimulation. Hypo-osmolar medium mimicked the effect of monensin, causing a 12-fold transient increase in beta-endorphin secretion. This effect was not abolished in either calcium-free or sodium-free medium. No increase in the number of exocytotic figures captured by tannic acid incubation was observed during 5 min of incubation with 1 mu M monensin or hypo-somolar medium. We thus show that monensin causes beta-endorphin secretion from the melanotrope and that this effect is due to sodium influx and resultant cell swelling. The calcium independency and lack of increase of exocytotic figures suggest that swelling-induced secretion is nonexocytotic, possibly via transient exocytotic pore opening. Copyright (C) 2000 S. Karger AG, Basel.
引用
收藏
页码:99 / 106
页数:8
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