Trischitta Francesca, Pidalà Patrizia, Faggio Caterina
Dipartimento di Fisiologia Generale e Farmacologia, Università di Messina, Salita Sperone, 31, 98166 Sant'Agata-Messina,
Comp Biochem Physiol A Mol Integr Physiol. 2007 Oct;148(2):368-73. doi: 10.1016/j.cbpa.2007.05.025. Epub 2007 Jun 7.
We investigated the role of NO (nitric oxide) in the isolated intestine of the sea water adapted eel, by testing the effect of various donors on I(sc) (short-circuit current), due to net Cl(-) absorption in the control conditions. We found that the endogenous NO-synthase substrate l-arginine as well as two different NO donors, SNP (sodium nitroprusside) and SIN-1 (3-morpholinosydnonimine), produced a slow and gradual decrease of I(sc). The effect of SNP was reduced by the pretreatment with ODQ (1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one), a specific inhibitor of the soluble guanylyl cyclase, suggesting the involvement of cGMP (cyclic GMP) in some physiological actions of NO. The effect of the NO donors on I(sc) was similar to that observed when the tissues were perfused with solution in which the HCO(3)(-) buffer was substituted with Hepes buffer. In addition the NO donors produced a negligible effect on I(sc) when the tissues were perfused with Hepes buffer or in the presence of bilateral SITS(4-Acetoamido-4'-iso-thiocyanatostilbene-2,2'disulphonic acid), an inhibitor of the HCO(3)(-) transport mechanisms, operating on both cell membranes of the eel enterocyte and responsible for HCO(3)(-) uptake by the cell. Based on these observations we suggest that NO regulates I(sc) and hence the transepithelial ion transport indirectly by modulating the endocellular concentration of HCO(3)(-) and/or H(+). In addition it is likely that NO modulates the permeability of the paracellular pathway since SNP produced also an increase of the tissue conductance and a decrease of the magnitude of the dilution potential.
我们通过测试各种供体对短路电流（Isc）的影响，研究了一氧化氮（NO）在适应海水的鳗鱼离体肠道中的作用，该短路电流是在对照条件下由于净氯离子（Cl-）吸收产生的。我们发现内源性NO合酶底物L-精氨酸以及两种不同的NO供体，硝普钠（SNP）和3-吗啉代硫代亚胺（SIN-1），会使Isc缓慢逐渐降低。用可溶性鸟苷酸环化酶的特异性抑制剂ODQ（1H-[1,2,4]恶二唑并-[4,3-a]喹喔啉-1-酮）预处理可降低SNP的作用，这表明环磷酸鸟苷（cGMP）参与了NO的某些生理作用。NO供体对Isc的作用与用Hepes缓冲液替代HCO3-缓冲液灌注组织时观察到的作用相似。此外，当用Hepes缓冲液灌注组织或在存在双侧4-乙酰氨基-4'-异硫氰基芪-2,2'-二磺酸（SITS）（一种HCO3-转运机制抑制剂，作用于鳗鱼肠上皮细胞的两个细胞膜并负责细胞对HCO3-的摄取）时，NO供体对Isc的影响可忽略不计。基于这些观察结果，我们认为NO通过调节细胞内HCO3-和/或H+的浓度间接调节Isc，从而调节跨上皮离子转运。此外，NO可能调节细胞旁途径的通透性，因为SNP还导致组织电导增加和稀释电位幅度降低。
