Uesaka T, Yano K, Sugimoto S, Ando M
Laboratory of Physiology, Faculty of Integrated Arts and Sciences, Hiroshima University, Japan.
Zoolog Sci. 1996 Jun;13(3):341-6. doi: 10.2108/zsj.13.341.
A neuropeptide Y (eNPY) was isolated from the intestinal extract of eels. This peptide enhanced significantly the serosa-negative transepithelial potential difference (PD) and short-circuit current (Isc) across the intestine of the seawater eel after pretreatment with isobutylmethylxanthine, serotonin and methacholine. The effects of eNPY on the Isc were concentration-dependent with a threshold concentration of 3 x 10(-9) M and a maximal effect at 3 x 10(-7) M. Similar concentration-response curve was obtained by porcine peptide YY (pPYY). Since 9 amino acid residues are replaced in the pPYY, this result indicates that these substitutions do not change the potency and the efficacy. These stimulatory actions of eNPY were not blocked by tetrodotoxin, an inhibitor of neural firing, or yohimbine, an alpha 2-adrenoceptor antagonist, indicating that eNPY acts without enteric neural firing or catecholamine release. When eNPY and adrenaline (AD) were applied simultaneously, the effects were additive only at lower dosage (3 x 10(-8) M for eNPY, 3 x 10(-8) M for AD), but not at high dosage (10(-6) M eNPY, 10(-7) M AD). The ceiling effect at high dosage suggests that these two regulators act through common signal transduction systems and affect the Na(+)-K(+)-Cl- cotransport system, since both effects were completely blocked by bumetanide, a specific inhibitor of Na(+)-K(+)-Cl- cotransporter.
一种鳗鱼神经肽Y（eNPY）是从鳗鱼肠道提取物中分离出来的。在用异丁基甲基黄嘌呤、血清素和乙酰甲胆碱预处理后，这种肽显著增强了海水鳗鱼肠道的浆膜负跨上皮电位差（PD）和短路电流（Isc）。eNPY对Isc的作用呈浓度依赖性，阈值浓度为3×10⁻⁹ M，最大效应在3×10⁻⁷ M。猪肽YY（pPYY）也得到了类似的浓度-反应曲线。由于pPYY中有9个氨基酸残基被替换，这一结果表明这些替换不会改变效力和功效。eNPY的这些刺激作用不受神经放电抑制剂河豚毒素或α₂肾上腺素能受体拮抗剂育亨宾的阻断，这表明eNPY的作用无需肠神经放电或儿茶酚胺释放。当同时应用eNPY和肾上腺素（AD）时，仅在较低剂量（eNPY为3×10⁻⁸ M，AD为3×10⁻⁸ M）时效应呈相加性，而在高剂量（eNPY为10⁻⁶ M，AD为10⁻⁷ M）时则不然。高剂量时的天花板效应表明这两种调节剂通过共同的信号转导系统起作用，并影响Na⁺-K⁺-Cl⁻共转运系统，因为两种效应都被Na⁺-K⁺-Cl⁻共转运体的特异性抑制剂布美他尼完全阻断。
