FREE INTRACELLULAR CA2+ CONCENTRATION ([CA2+]I) AND GROWTH-HORMONE RELEASE FROM PURIFIED RAT SOMATOTROPHS .1. GH-RELEASING FACTOR-INDUCED CA2+ INFLUX RAISES [CA2+]I

被引:86
作者
LUSSIER, BT [1 ]
FRENCH, MB [1 ]
MOOR, BC [1 ]
KRAICER, J [1 ]
机构
[1] UNIV WESTERN ONTARIO,HLTH SCI CTR,DEPT PHYSIOL,LONDON N6A 5C1,ONTARIO,CANADA
关键词
D O I
10.1210/endo-128-1-570
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
This study was carried out to investigate the role of free intracellular Ca2+ ([Ca2+]i) in the action of GH-releasing factor (GRF) by determining whether GRF causes an increase in [Ca2+]i and whether this increase results from changes in Ca2+ influx/efflux and/or mobilization of intracellular Ca2+ stores. We used a purified preparation of normal rat somatotrophs and examined the changes in Ca-45 uptake, [Ca2+]i measured with indo-1, tracellular cAMP, and GH release induced by GRF. GRF stimulated a concentration-related biphasic increase in [Ca2+]i. Both the GRF-dependent increase in [Ca2+]i and GH release were blocked by incubation in low Ca2+ medium and by the organic Ca2+ antagonists nifedipine and diltiazem. The measurement of Ca-45 uptake, in both steady state and nonsteady state conditions, demonstrated directly that GRF stimulates Ca2+ influx into somatotrophs. These data demonstrate that the GRF-stimulated increase in [Ca2+]i, is dependent on Ca2+ influx. Redistribution of intracellularly stored Ca2+ could not be detected, even though intracellular Ca2+ stores were present. Therefore, the increase is due to Ca2+ influx, and the biphasic nature of the increase in [Ca2+]i induced by GRF is due to a difference in the rate of activation of Ca2+ influx and Ca2+ removal from the cytosol.
引用
收藏
页码:570 / 582
页数:13
相关论文
共 59 条