School of Biological Sciences, The University of Hong Kong, Hong Kong, China.
Mol Cell Endocrinol. 2013 Jul 15;374(1-2):22-34. doi: 10.1016/j.mce.2013.04.003. Epub 2013 Apr 16.
In grass carp, luteinizing hormone (LH) can act locally within the pituitary to regulate growth hormone expression. To test if LH receptor (LHR) expression in the carp pituitary can also serve as a target of modulation for LH actions, grass carp LHR was cloned and characterized by functional expression. In carp pituitary cells, LHR mRNA (lhr) level could be reduced by LH or human chorionic gonadotropin (hCG) but up-regulated by dopamine treatment. Dopamine-induced lhr expression occurred mainly in carp somatotrophs via the cAMP/PKA pathway coupled to pituitary D1 receptors. This stimulatory effect could be blocked by LHR activation by hCG, presumably through phosphodiesterase III activation. These findings provide evidence that lhr expression in the carp pituitary is under the differential control of LH and dopamine via modification of cAMP-dependent signaling mechanisms, which may play a role in regulating somatotroph responsiveness to the paracrine action of LH in carp species.
在草鱼中，促黄体激素 (LH) 可以在垂体中发挥局部作用，调节生长激素的表达。为了测试草鱼垂体中的 LH 受体 (LHR) 表达是否也可以作为 LH 作用的调节靶点，我们通过功能表达克隆并表征了草鱼 LHR。在草鱼垂体细胞中，LH 或人绒毛膜促性腺激素 (hCG) 可降低 LHR mRNA (lhr) 水平，但多巴胺处理可上调 lhr 表达。多巴胺诱导的 lhr 表达主要发生在草鱼生长激素细胞中，通过与垂体 D1 受体偶联的 cAMP/PKA 途径。hCG 通过激活 LHR 可阻断这种刺激作用，可能通过磷酸二酯酶 III 激活。这些发现提供了证据表明，草鱼垂体中的 lhr 表达受 LH 和多巴胺的差异调控，通过改变 cAMP 依赖性信号机制，这可能在调节生长激素细胞对 LH 旁分泌作用的反应性方面发挥作用。
