The intestinal peptides guanylin and uroguanylin regulate the electrolyte/water transport in the gastrointestinal epithelium via activation of cystic fibrosis transmembrane conductance regulator (CFTR), the cystic fibrosis gene product. Because a major but incompletely understood function of the salivary glands is the CFTR-mediated secretion of an electrolyte-rich fluid, we investigated the rat and guinea pig parotid and submandibular glands for expression, cellular distribution, and subcellular localization of guanylin and uroguanylin. RT-PCR analyses with guanylin and uroguanylin-specific primers revealed that both peptides are highly expressed in the parotid and submandibular glands. At the translational level, western blotting analyses with peptide-specific guanylin and uroguanylin antibodies identified the expected 12.5-kDa immunoreactive peptides in these organs. At the cellular level, guanylin and uroguanylin were exclusively confined to epithelial cells of the intralobular and interlobular ducts. At the subcellular level, the immunoreactivities were localized by preembedding immunoelectron microscopy to small vesicles which were concentrated at the apical part of the secretory epithelial cells. The expression and cell-specific localization of guanylin and uroguanylin in the salivary glands indicate that these peptides may be specifically involved in the regulation of CFTR-mediated electrolyte/water secretion in the salivary gland ductal system.

中文翻译：

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腮腺和颌下腺中的鸟苷和尿鸟苷：唾液腺中电解质分泌的潜在内在调节剂。

肠肽鸟苷蛋白和尿鸟苷蛋白通过激活囊性纤维化跨膜电导调节剂（CFTR）来调节胃肠道上皮中的电解质/水运输，CFTR是囊性纤维化的基因产物。由于唾液腺的主要但尚未完全理解的功能是CFTR介导的富含电解质的液体的分泌，因此我们研究了大鼠和豚鼠的腮腺和下颌下腺的鸟苷蛋白和尿鸟苷蛋白的表达，细胞分布以及亚细胞定位。用鸟苷蛋白和尿鸟苷蛋白特异性引物进行的RT-PCR分析表明，两种肽均在腮腺和下颌下腺中高表达。在翻译水平上，用肽特异性鸟苷蛋白和尿鸟苷蛋白抗体进行的蛋白质印迹分析确定了预期的12。这些器官中的5 kDa免疫反应性肽。在细胞水平上，鸟苷蛋白和尿鸟苷蛋白仅局限于小叶内和小叶间导管的上皮细胞。在亚细胞水平上，通过预先嵌入的免疫电子显微镜将免疫反应性定位在小囊泡上，这些小囊泡集中在分泌上皮细胞的顶端。鸟苷和尿鸟苷在唾液腺中的表达和细胞特异性定位表明，这些肽可能特异性参与唾液腺导管系统中CFTR介导的电解质/水分泌的调节。通过预先嵌入免疫电子显微镜将免疫反应性定位在小囊泡上，这些小囊泡集中在分泌上皮细胞的顶端。鸟苷和尿鸟苷在唾液腺中的表达和细胞特异性定位表明，这些肽可能特异性参与唾液腺导管系统中CFTR介导的电解质/水分泌的调节。通过预先嵌入免疫电子显微镜将免疫反应性定位在小囊泡上，这些小囊泡集中在分泌上皮细胞的顶端。鸟苷和尿鸟苷在唾液腺中的表达和细胞特异性定位表明，这些肽可能特异性参与唾液腺导管系统中CFTR介导的电解质/水分泌的调节。