Dopamine actions on calcium currents, potassium currents and hormone release in rat melanotrophs.
Dopamine actions on calcium currents, potassium currents and hormone release in rat melanotrophs.
复制标题
多巴胺对大鼠黑素细胞中钙电流、钾电流和激素释放的作用。
DOI：
10.1113/jphysiol.1991.sp018655
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Surprenant,A
中科院分区：
文献类型：
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作者：
Stack,J;Surprenant,A
1.用原代培养的大鼠中间叶垂体细胞进行细胞内和全细胞记录，并用放射免疫法测定β-内啡肽的分泌。比较多巴胺受体激活对激素分泌、钙电流和静息钾电导的影响。2.用细胞内微电极和全细胞膜片电极分别记录到82%和%的细胞出现自发的钠依赖性动作电位，在河豚毒素存在下，同样比例的细胞出现自发的钙依赖性去极化。3.保持电位为-90 mV和-70 mV时，记录到的钙电流有瞬变和持续两种成分，均在-40 mV时激活，具有相似的电流-电压关系。Bay K 8644(1微米)使这两种成分增加约130%，而硝苯地平(1-10微米)最多使它们减少30%。镍(500微米)对瞬变和持续成分的抑制作用分别为68%和50%；镉(100微米)则使电流消失。欧米茄-芋毒素(1微米)对瞬变成分的可逆抑制作用为26%。4.多巴胺D2受体激动剂奎比罗(0.1-10微米)对所有细胞的暂时性成分和持续性成分的抑制率分别高达40%和25%。昆比罗尔没有改变洋流的时间进程。5.昆匹罗(1-100 nM)超极化90%的细胞进行细胞内记录，55%的细胞使用全细胞膜片移液管记录。100 nM喹比罗可使静息电位从-44+/-5 mV最大超极化为16+/-4 mV，产生半最大效应的浓度为3 nM。超极化是由于钾电导增加所致。6.喹比罗(1-100 nM)可使基础β-内啡肽分泌减少55%，并可阻断Bay K 8644或异丙肾上腺素刺激的分泌，半数抑制浓度为5-10 nM。河豚毒素(1微米)、硝苯地平(1微米)、镍(500微米)和镉(100微米)不改变基础分泌或刺激分泌，尽管较高浓度的镉会抑制刺激的激素释放。7.百日咳毒素预处理可阻断喹比罗的所有作用。8.因此，取消刺激激素分泌的喹比罗浓度不改变钙电流；相反，部分或完全抑制钙电流的钙通道阻滞剂浓度不改变基础或刺激分泌。这些结果可能表明，通过这些实验中测量的电压依赖性钙通道的钙内流对黑素营养素的激素释放没有显著的贡献。
1. Intracellular and whole‐cell recordings were made from primary cultures of rat intermediate pituitary cells; beta‐endorphin secretion was also measured by radioimmunoassay. The effects of dopamine receptor activation on hormone secretion, calcium currents and resting potassium conductance were compared. 2. Spontaneous sodium‐dependent action potentials occurred in 82% of cells recorded with intracellular microelectrodes and 64% of cells recorded with whole‐cell patch electrodes; the same proportion of cells showed spontaneous calcium‐dependent depolarizations in the presence of tetrodotoxin. 3. Calcium currents recorded from holding potentials of ‐90 or ‐70 mV showed transient and sustained components, both of which activated at ‐40 mV and had similar current‐voltage relations. Bay K 8644 (1 microM) increased both components by about 130% while nifedipine (1‐10 microM) decreased them by a maximum of 30%. Nickel (500 microM) inhibited transient and sustained components by 68 and 50%; cadmium (100 microM) abolished the current. omega‐Conotoxin (1 microM) reversibly inhibited the transient component by 26%. 4. The dopamine D2 receptor agonist, quinpirole (0.1‐10 microM) inhibited transient and sustained components in all cells by a maximum of 40 and 25% respectively. Quinpirole did not alter the time course of the current. 5. Quinpirole (1‐100 nM) hyperpolarized 90% of cells from which intracellular recordings were made and 55% of cells recorded from with whole‐cell patch pipettes. Maximum hyperpolarization of 16 +/‐ 4 mV from a resting potential of ‐44 +/‐ 5 mV was observed with 100 nM‐quinpirole; concentration producing half‐maximal effect was 3 nM. The hyperpolarization resulted from an increase in potassium conductance. 6. Quinpirole (1‐100 nM) decreased basal beta‐endorphin secretion by 55% and abolished secretion stimulated by Bay K 8644 or isoprenaline; concentrations producing half‐maximal inhibitions were 5‐10 nM. Tetrodotoxin (1 microM), nifedipine (1 microM), nickel (500 microM) and cadmium (100 microM) did not alter basal or stimulated secretion although higher concentrations of cadmium did inhibit stimulated hormone release. 7. Pertussis toxin pre‐treatment prevented all actions of quinpirole. 8. Thus, concentrations of quinpirole that abolished stimulated hormone secretion did not alter calcium currents; conversely, concentrations of calcium channel blockers that partially or completely inhibited calcium currents did not alter basal or stimulated secretion. These results may indicate that calcium influx through the voltage‐dependent calcium channels measured in these experiments does not contribute significantly to hormone release from melanotrophs.(ABSTRACT TRUNCATED AT 400 WORDS)