Login I S, Judd A M, Macleod R M
Department of Neurology, University of Virginia School of Medicine, Charlottesville.
Cell Calcium. 1988 Feb;9(1):27-31. doi: 10.1016/0143-4160(88)90035-8.
Cells of the 7315a prolactin-secreting tumour express biochemically normal cell-surface receptors for dopamine. However, dopamine inhibits prolactin release from these cells only when the basal rate of prolactin release is augmented by increasing the intracellular and/or extracellular calcium concentration of the tumour cells. This suggests that dopaminergic modulation of calcium ion flux could have a central physiological role in these neoplastic cells. In 7315a cells we examined the ability of dopamine to regulate 45Ca2+ influx and fractional 45Ca2+ efflux under conditions of enhanced calcium flux using the calcium channel activator, maitotoxin. It was observed that unidirectional calcium influx stimulated by maitotoxin was significantly inhibited by dopamine. Maitotoxin stimulated fractional efflux and prolactin release from the tumour cells and dopamine simultaneously inhibited both processes by a haloperidol-reversible mechanism. Therefore, in 7315a cells dopamine receptor activation is coupled to inhibition of calcium flux as at least one component in the regulation of prolactin release. These cells may provide further opportunity to study intracellular signalling mechanisms that are modulated by dopamine receptor activity.
7315a催乳素分泌肿瘤细胞表达生化性质正常的多巴胺细胞表面受体。然而，多巴胺仅在通过增加肿瘤细胞的细胞内和/或细胞外钙浓度来提高催乳素释放的基础速率时，才会抑制这些细胞释放催乳素。这表明多巴胺能对钙离子通量的调节可能在这些肿瘤细胞中具有核心生理作用。在7315a细胞中，我们使用钙通道激活剂 maitotoxin，在增强钙通量的条件下研究了多巴胺调节45Ca2+内流和45Ca2+分数外流的能力。观察到，maitotoxin刺激的单向钙内流被多巴胺显著抑制。Maitotoxin刺激肿瘤细胞的分数外流和催乳素释放，而多巴胺通过氟哌啶醇可逆机制同时抑制这两个过程。因此，在7315a细胞中，多巴胺受体激活与钙通量的抑制相关联，这是催乳素释放调节中的至少一个组成部分。这些细胞可能为研究受多巴胺受体活性调节的细胞内信号传导机制提供更多机会。
