Israel J M, Jaquet P, Vincent J D
Endocrinology. 1985 Oct;117(4):1448-55. doi: 10.1210/endo-117-4-1448.
Human prolactinoma cells were maintained in culture for a period of at least 8 days and were able to secrete PRL in large amounts. This secretion was inhibited by bromocriptine, an agonist of dopaminergic receptors, in a dose-dependent manner. The cells showed electrical activity (action potentials) which was blocked by inhibitors of calcium current (cobalt, manganese), whereas it was insensitive to blockers of sodium current (tetrodotoxin). At the resting potential of the cell, dopamine induced a hyperpolarizing response such that action potentials no longer occurred. This effect was due to increase of the membrane conductance and depended on the cell potential. The reversal potential of this response was at -100 mV, which suggests the involvement of potassium ions. Bromocriptine and RU 24213, which are strong dopaminergic receptor agonists, both induced responses identical to the dopamine-induced response. The D2 receptor antagonists (haloperidol, domperidone, and spiperone) blocked the dopamine-induced response in a reversible manner. The D1 antagonist of dopaminergic receptors flupentixol had no effect on the dopamine response. It is concluded that the dopamine modulation of electrical activity involving calcium current may be an early important step in the mechanism by which dopamine inhibits PRL release.
人催乳素瘤细胞在培养中维持至少8天，并能够大量分泌催乳素（PRL）。这种分泌受到多巴胺能受体激动剂溴隐亭的剂量依赖性抑制。这些细胞表现出电活动（动作电位），该电活动被钙电流抑制剂（钴、锰）阻断，而对钠电流阻断剂（河豚毒素）不敏感。在细胞的静息电位下，多巴胺诱导超极化反应，使得动作电位不再出现。这种效应是由于膜电导增加，并且取决于细胞电位。该反应的反转电位为 -100 mV，这表明钾离子参与其中。溴隐亭和RU 24213，这两种强效多巴胺能受体激动剂，均诱导出与多巴胺诱导的反应相同的反应。D2受体拮抗剂（氟哌啶醇、多潘立酮和螺哌隆）以可逆方式阻断多巴胺诱导的反应。多巴胺能受体的D1拮抗剂氟哌噻吨对多巴胺反应没有影响。结论是，多巴胺对涉及钙电流的电活动的调节可能是多巴胺抑制PRL释放机制中的一个早期重要步骤。
