Pozzoli G, Bilezikjian L M, Perrin M H, Blount A L, Vale W W
Clayton Foundation Laboratories for Peptide Biology, Salk Institute, La Jolla, California 92037-1099, USA.
Endocrinology. 1996 Jan;137(1):65-71. doi: 10.1210/endo.137.1.8536643.
Previous studies involving radioreceptor and functional assays have shown that CRF and glucocorticoids are able to modulate CRF receptors of the brain and anterior pituitary. In this study, we analyzed the effects of CRF, vasopressin (AVP), dexamethasone (DEX), and corticosterone on the regulation of CRF receptor (CRF-R1) messenger RNA (mRNA) levels in cultured rat anterior pituitary cells. CRF decreased CRF-R1 mRNA levels in a time- and concentration-dependent manner. In the presence of 10 nM CRF, CRF-R1 mRNA levels decreased within 1 h (to 65 +/- 3% of the control value; P < 0.01) with a maximal effect after 3 h (to 28 +/- 1% of the control value; P < 0.001). The concentration dependence of the inhibitory effect of CRF at 3 h correlated with that required for ACTH secretion (half-maximal at approximately 0.03 nM). Treatment with a maximal (100 nM) dose of AVP or a submaximal (0.1 nM) dose of CRF for 3 h reduced CRF-R1 mRNA levels to 66 +/- 3% and 53 +/- 6% of the control value, respectively. In the presence of both AVP and CRF, CRF-R1 mRNA levels were 32 +/- 3% of the control value. The incubation of cells for 3 h with 10 microM forskolin to activate adenylate cyclase or with 20 nM 12-0-tetradecanoylphorbol-13-acetate to activate protein kinase C resulted in a decrease in receptor mRNA levels to 40 +/- 9% (P < 0.01) and 28 +/- 8% (P < 0.001) of the control value, respectively, suggesting that the effects of CRF and AVP may be mediated by these pathways. DEX (20 nM) also caused a dose- and time-dependent decrease in mRNA levels. Maximal inhibition was observed after 3 h (to 31 +/- 6% of the control value; P < 0.001), with a partial recovery of mRNA levels at 24 or 48 h. Corticosterone similarly inhibited the accumulation of CRF-R1 mRNA in a dose- and time-dependent manner, but, in contrast to DEX, CRF-R1 mRNA levels returned almost to control levels after 24 h. These results indicate that the ability of CRF, AVP, and glucocorticoids to modulate the responses of corticotropes to CRF may be due in part to the actions of these agents on CRF-R1 mRNA accumulation.
先前涉及放射受体和功能测定的研究表明，促肾上腺皮质激素释放因子（CRF）和糖皮质激素能够调节大脑和垂体前叶的CRF受体。在本研究中，我们分析了CRF、血管加压素（AVP）、地塞米松（DEX）和皮质酮对培养的大鼠垂体前叶细胞中CRF受体（CRF-R1）信使核糖核酸（mRNA）水平调节的影响。CRF以时间和浓度依赖性方式降低CRF-R1 mRNA水平。在存在10 nM CRF的情况下，CRF-R1 mRNA水平在1小时内下降（降至对照值的65±3%；P<0.01），3小时后达到最大效应（降至对照值的28±1%；P<0.001）。CRF在3小时时抑制作用的浓度依赖性与促肾上腺皮质激素（ACTH）分泌所需的浓度依赖性相关（约0.03 nM时达到半数最大效应）。用最大剂量（100 nM）的AVP或次最大剂量（0.1 nM）的CRF处理3小时，CRF-R1 mRNA水平分别降至对照值的66±3%和53±6%。在同时存在AVP和CRF的情况下，CRF-R1 mRNA水平为对照值的32±3%。用10 μM福斯可林孵育细胞3小时以激活腺苷酸环化酶或用20 nM 12-0-十四烷酰佛波醇-13-乙酸酯孵育细胞3小时以激活蛋白激酶C，导致受体mRNA水平分别降至对照值的40±9%（P<0.01）和28±8%（P<0.001），这表明CRF和AVP的作用可能是通过这些途径介导的。DEX（20 nM）也导致mRNA水平呈剂量和时间依赖性下降。3小时后观察到最大抑制作用（降至对照值的31±6%；P<0.001），在24或48小时时mRNA水平部分恢复。皮质酮同样以剂量和时间依赖性方式抑制CRF-R1 mRNA的积累，但与DEX不同的是，24小时后CRF-R1 mRNA水平几乎恢复到对照水平。这些结果表明，CRF、AVP和糖皮质激素调节促肾上腺皮质激素细胞对CRF反应的能力可能部分归因于这些物质对CRF-R1 mRNA积累的作用。
