Buck Christine, Schaeffel Frank, Simon Perikles, Feldkaemper Marita
Section of Neurobiology of the Eye, University Eye Hospital, Tübingen, Tübingen, Germany.
Invest Ophthalmol Vis Sci. 2004 Feb;45(2):402-9. doi: 10.1167/iovs.03-0789.
It has been found in the chicken that the amount of retinal glucagon mRNA increases during treatment with positive lenses. Pharmacological studies support the idea that glucagon may act as a stop signal for visually induced eye growth. To gain more insight into the functional role of glucagon, the changes of glucagon and glucagon receptor mRNA concentrations in retina and choroid over time were studied. Furthermore, the abundance of glucagon and the glucagon receptor was studied in different fundal layers (retina, retinal pigment epithelium[RPE], choroid) and the blood.
Semiquantitative real-time RT-PCR was used to measure glucagon and glucagon receptor mRNA levels in retina and choroid after positive and negative lens treatment for 2, 6, or 24 hours, by unilateral -7- or +7-D lenses. Contralateral eyes served as the control, and completely untreated animals provided further reference data. Intravitreal colchicine injections (which are known to reduce the number of glucagon cells sharply) were used to verify that the related decline in glucagon mRNA could be measured by real-time RT-PCR.
In the retina, treatment with -7-D lenses induced an initial upregulation of glucagon mRNA in both eyes, followed by a significant downregulation. The treatment with +7-D lenses showed a significant but transient downregulation in the control eye superimposed on a trend toward upregulation in the treated eye. However, the changes in glucagon mRNA expression were not confined to the lens-treated eyes but were also found, although sometimes to a lesser extent, in the non-lens-covered fellow eyes. There was evidence of a transient increase in glucagon receptor mRNA levels in lens-treated eyes after either -7- or +7-D lens wear. In the choroid, no effect of imposed defocus was detected. The injection of colchicine led to the destruction of approximately 75% of the glucagon amacrine cells but the mRNA level of retinal glucagon decreased by only approximately 50%. Glucagon receptor expression was found to be higher in the RPE than the retina and choroid whereas, in the blood, glucagon and glucagon receptor mRNA expression was below detection level.
The observed bidirectional regulation of glucagon mRNA in correlation with the sign of imposed defocus supports the idea that glucagon may act as a stop-and-go signal for eye growth. This is in line with a previous proposal based on studies of changes of the glucagon peptide content.
研究发现，在鸡中，正透镜处理期间视网膜胰高血糖素mRNA的量会增加。药理学研究支持胰高血糖素可能作为视觉诱导的眼球生长的停止信号这一观点。为了更深入了解胰高血糖素的功能作用，研究了视网膜和脉络膜中胰高血糖素和胰高血糖素受体mRNA浓度随时间的变化。此外，还研究了不同眼底层（视网膜、视网膜色素上皮[RPE]、脉络膜）和血液中胰高血糖素和胰高血糖素受体的丰度。
使用半定量实时RT-PCR测量单侧-7-或+7-D透镜处理2、6或24小时后视网膜和脉络膜中胰高血糖素和胰高血糖素受体mRNA水平。对侧眼作为对照，完全未处理的动物提供进一步的参考数据。玻璃体内注射秋水仙碱（已知可大幅减少胰高血糖素细胞数量）用于验证实时RT-PCR可测量胰高血糖素mRNA的相关下降。
在视网膜中，-7-D透镜处理在两只眼睛中均诱导了胰高血糖素mRNA的初始上调，随后显著下调。+7-D透镜处理在对照眼中显示出显著但短暂的下调，叠加在处理眼中的上调趋势之上。然而，胰高血糖素mRNA表达的变化不仅限于透镜处理的眼睛，在未被透镜覆盖的对侧眼中也有发现，尽管有时程度较小。有证据表明，佩戴-7-或+7-D透镜后，透镜处理的眼睛中胰高血糖素受体mRNA水平短暂增加。在脉络膜中，未检测到人为散焦的影响。注射秋水仙碱导致约75%的胰高血糖素无长突细胞被破坏，但视网膜胰高血糖素的mRNA水平仅下降约50%。发现胰高血糖素受体在RPE中的表达高于视网膜和脉络膜，而在血液中，胰高血糖素和胰高血糖素受体mRNA表达低于检测水平。
观察到的胰高血糖素mRNA与人为散焦信号相关的双向调节支持了胰高血糖素可能作为眼球生长的停止和启动信号的观点。这与先前基于胰高血糖素肽含量变化研究提出的建议一致。
