THYROTROPIN-RELEASING-HORMONE STIMULATION OF PROLACTIN-RELEASE FROM CLONAL RAT PITUITARY-CELLS - EVIDENCE FOR ACTION INDEPENDENT OF EXTRACELLULAR CALCIUM
THYROTROPIN-RELEASING-HORMONE STIMULATION OF PROLACTIN-RELEASE FROM CLONAL RAT PITUITARY-CELLS - EVIDENCE FOR ACTION INDEPENDENT OF EXTRACELLULAR CALCIUM
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DOI：
10.1172/jci110216
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发表时间：
1981-01-01
影响因子：
15.9
通讯作者：
RUBIN, BG
中科院分区：
文献类型：
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作者：
GERSHENGORN, MC;HOFFSTEIN, ST;RUBIN, BG
促甲状腺激素释放激素（TRH）刺激大鼠垂体细胞克隆株GH 3细胞的催乳素[PRL]释放和45 Ca 2+外流。细胞外K+升高也诱导PRL释放，并增加45 Ca 2+流出这些细胞。本文区分了TRH和高K ~+作为促性腺激素的作用，并指出TRH诱导的PRL释放和~（45）Ca ~（2+）外流与细胞外Ca ~（2+）浓度无关，而高K ~+对PRL释放和~（45）Ca ~（2+）外流的影响则依赖于培养液中Ca ~（2+）浓度。通过将细胞外Ca 2+从1500 μ M降低至0.02 μ M（通过加入乙二醇-双（β-葡萄糖）），以浓度依赖性方式降低了在灌注期间由50 mM K+诱导的45 Ca 2+流出的增量。氨基乙基醚）N，N，N“，N”-四乙酸; 1 μ M TRH在整个细胞外Ca 2+浓度范围内类似地增强45 Ca 2+流出。尽管50 mM K+引起40 × 10 - 6细胞释放150 ng PRL，106 GH 3细胞暴露于1500 μ M Ca 2+（对照），细胞外Ca 2+降低至2.8 μ M使由高K+引起的PRL释放降低至对照的< 3%，并且在具有0.02 μ M游离Ca 2+的培养基中暴露于50 mM K+后未检测到PRL释放。相比之下，TRH引起从40 x中释放64 ng的PRL。将106个GH 3细胞暴露于具有1500 μ M Ca 2+的培养基，并且TRH引起的释放仍然分别是具有2.8和0.02 μ M Ca 2+的培养基中对照的50%和35%。在与1500或3.5 μ M Ca 2+的静态孵育中，TRH使来自GH 3细胞的45 Ca 2+流出分数瞬时增加10倍，证实在低和高Ca 2+培养基中由TRH引起的增强的45 Ca 2+流出不是灌流系统的人为产物。金霉素（CTC），膜结合的Ca 2+的探针，获得的数据与通过测量45 Ca 2+流出得到的一致。CTC的荧光强度随细胞外Ca ~（2+）浓度和孵育时间的变化而变化。TRH降低了细胞相关的CTC的荧光的方式强烈建议刺激诱导的动员的Ca 2+，这种效果仍然是证明在GH 3细胞孵育在50 mM K+。显然，TRH的作用是动员被隔离的细胞相关的Ca 2+，反映为45 Ca 2+流出，这是独立于细胞外Ca 2+浓度。游离Ca ~（2+）向胞浆内的移动可提高胞内游离Ca ~（2+），并使TRH刺激与PRL分泌偶联。
Thyrotropin-releasing hormone (TRH) stimulates prolactin [PRL] release and 45Ca2+ efflux from GH3 cells, a clonal strain of rat pituitary cells. Elevation of extracellular K+ also induces PRL release and increases 45Ca2+ efflux from these cells. This report distinguishes between TRH and high K+ as esecretagogues and shows that TRH-induced release of PRL and 45Ca2+ efflux is independent of the extracellular Ca2+ concentration, but the effect of high K+ on PRL release and 45Ca2+ efflux is dependent on the concentration of Ca2+ in the medium. The increment in 45Ca2+ efflux induced by 50 mM K+ during perifusion was reduced in a concentration-dependent manner by lowering extracellular Ca2+ from 1500 to 0.02 .mu.M (by adding ethylene glycol-bis(.beta.-amino ethyl ether)N,N,N'',N''-tetraacetic acid; 1 .mu.M TRH enhanced 45Ca2+ efflux similarly over the entire range of extracellular Ca2+ concentrations. Although 50 mM K+ caused release of 150 ng PRL from 40 .times. 106 GH3 cells exposed to 1500 .mu.M Ca2+ (control), reduction of extracellular Ca2+ to 2.8 .mu.M decreased PRL release caused by high K+ to < 3% of controls and no PRL release was detected after exposure to 50 mM K+ in medium with 0.02 .mu.M free Ca2+. In contrast, TRH caused release of 64 ng of PRL from 40 .times. 106 GH3 cells exposed to medium with 1500 .mu.M Ca2+, and release caused by TRH was still 50 and 35% of control in medium with 2.8 and 0.02 .mu.M Ca2+, respectively. TRH transiently increased by 10-fold the fractional efflux of 45Ca2+ from GH3 cells in static incubations with 1500 or 3.5 .mu.M Ca2+, confirming that the enhanced 45Ca2+ efflux caused by TRH in both low and high Ca2+ medium was not an artifact of the perifusion system. Data obtained with chlortetracycline (CTC), a probe of membrane-bound Ca2+, were concordant with those obtained by measuring 45Ca2+ efflux. Cellular fluorescence of CTC varied with the extracellular Ca2+ concentration and the duration of incubation. TRH decreased the fluoresence of cell-associated CTC in a manner strongly suggesting stimulus-induced mobilization of Ca2+, and this effect was still demonstrable in GH3 cells incubated in 50 mM K+. Apparently, TRH acts to mobilize sequestered cell-associated Ca2+ reflected as a 45Ca2+ efflux which is independent of the extracellular Ca2+ concentration. Mobilization of sequestered Ca2+ into the cytoplasm may elevate free intracellular Ca2+ and serve to couple stimulation by TRH to secretion of PRL.