Cao L, Blute T A, Eldred W D
Department of Biology, Boston University, MA 02215, USA.
Vis Neurosci. 2000 May-Jun;17(3):319-29. doi: 10.1017/s0952523800173018.
Heme oxygenase-2 (HO-2) synthesizes carbon monoxide (CO), a modulator of soluble guanylate cyclase (sGC). To examine this signal transduction pathway in the retina, we immunocytochemically localized HO-2, and investigated the effects of CO on cGMP levels. In turtle, HO-2-like immunoreactivity (-LI) was in all photoreceptors, some amacrine cells, and in numerous bipolar and ganglion cells. HO-2-LI colocalized with sGC activity in many cells. In rat, HO-LI was found only in the inner retina, in ganglion and amacrine cells. In turtle, stimulation with CO alone primarily increased cGMP-LI in bipolar cells in the visual streak. Stimulation with a combination of CO and nitric oxide (NO) dramatically increased cGMP-LI throughout the retina, in comparison to the smaller increases seen with NO or CO alone. These data suggest that CO is an endogenous modulator of the sGC/cGMP signaling pathway in many retinal neurons, and can dramatically amplify NO-stimulated increases in cGMP.
血红素加氧酶-2（HO-2）可合成一氧化碳（CO），而一氧化碳是可溶性鸟苷酸环化酶（sGC）的一种调节剂。为了研究视网膜中的这条信号转导途径，我们采用免疫细胞化学方法对HO-2进行了定位，并研究了一氧化碳对环磷酸鸟苷（cGMP）水平的影响。在龟的视网膜中，HO-2样免疫反应性（-LI）存在于所有光感受器、一些无长突细胞以及众多双极细胞和神经节细胞中。HO-2-LI在许多细胞中与sGC活性共定位。在大鼠视网膜中，HO-LI仅在内层视网膜的神经节细胞和无长突细胞中被发现。在龟的视网膜中，单独用一氧化碳刺激主要使视带双极细胞中的cGMP-LI增加。与单独使用一氧化氮（NO）或一氧化碳时较小的增加相比，联合使用一氧化碳和一氧化氮刺激可使整个视网膜中的cGMP-LI显著增加。这些数据表明，一氧化碳是许多视网膜神经元中sGC/cGMP信号通路的内源性调节剂，并且能够显著放大一氧化氮刺激引起的cGMP增加。
