Overlease Ruth L, Bauer Roslyn A, Angleson Joseph K
Department of Biological Sciences, University of Denver, Denver, CO 80208, USA.
Pflugers Arch. 2005 Feb;449(5):458-62. doi: 10.1007/s00424-004-1352-8. Epub 2004 Oct 12.
The secretion of peptide hormones during exocytosis of an individual vesicle can result in either complete discharge of vesicle content or can occur in a partial manner in which some hormone is retained during transient fusion. In anterior pituitary lactotrophs, the retained hormone prolactin was internalized and recycled into a pool of vesicles that underwent preferential use during subsequent exocytic stimulations [Bauer et al., (2004) J Cell Sci. 117:2193-2202]. The aim of the present study was to determine whether retention and preferential recycling of retained hormones occurred in other anterior pituitary cells. Stimulation of somatotrophs with high K+ resulted in 50 discrete puncta per cell that were positive for growth hormone immunoreactivity. Identical stimulation of corticotrophs resulted in 150 puncta per cell that were anti-adrenocorticotrophic hormone (ACTH) positive. However, unlike what was observed for lactotrophs, the number of structures containing retained growth hormone and ACTH decreased to less than 10% of the initial value in 80 min in somatotrophs and in less than 10 min in corticotrophs. Our results indicate that functional recycling of retained hormones is not shared by all anterior pituitary cell types.
单个囊泡胞吐过程中肽类激素的分泌可能导致囊泡内容物完全释放，也可能以部分释放的方式进行，即一些激素在短暂融合过程中被保留。在垂体前叶催乳素细胞中，被保留的激素催乳素被内化并循环到一个囊泡池中，在随后的胞吐刺激过程中这些囊泡被优先利用[鲍尔等人，（2004年）《细胞科学杂志》。117:2193 - 2202]。本研究的目的是确定保留激素的保留和优先循环是否发生在其他垂体前叶细胞中。用高钾刺激生长激素细胞导致每个细胞出现50个离散的点，这些点对生长激素免疫反应呈阳性。对促肾上腺皮质激素细胞进行相同刺激导致每个细胞出现150个点，这些点对促肾上腺皮质激素（ACTH）呈阳性。然而，与催乳素细胞的情况不同，在生长激素细胞中，含有保留的生长激素和促肾上腺皮质激素的结构数量在80分钟内降至初始值的不到10%，而在促肾上腺皮质激素细胞中则在不到10分钟内降至初始值的不到10%。我们的结果表明，并非所有垂体前叶细胞类型都存在保留激素的功能性循环。
