Homann Veronika, Rosin-Steiner Sigrid, Stratmann Tina, Arnold Wolfgang H, Gaengler Peter, Kinne Rolf K-H
Abteilung Epithelphysiologie, Max-Planck-Institut für molekulare Physiologie, 44139 Dortmund, Germany.
Arch Oral Biol. 2005 Sep;50(9):759-68. doi: 10.1016/j.archoralbio.2005.01.009. Epub 2005 Mar 24.
In order to elucidate the cellular and molecular mechanisms of phosphate secretion by human salivary glands, the expression and intracellular distribution of sodium-phosphate cotransporters was investigated.
Total RNA was extracted from 33 parotid gland (PG) and 35 submandibular gland (SMG) samples and RT-PCR was performed using gene specific primers for all known sodium-phosphate cotransporters. An antibody was raised against an NPT2b epitope and the cellular and intracellular distribution was investigated by immunohistochemistry.
No mRNA for the type I cotransporter NPT1 was found. Out of the type II phosphate cotransporters only message for NPT2b but not for NPT2a or NPT2c could be detected in about the same number of samples (76% in PG versus 69% in SMG). Type III cotransporter mRNA was also found in both glands, PIT1 gave positive results for 93% of PG samples compared to 69% of SMG samples. For PIT2 also, a higher expression was found in PG than in SMG, although the difference was smaller (79% versus 51%). Immunostaining for NPT2b was found both in the acini and in the ducts, with a stronger reaction in the latter. In acinar cells, NPT2b was restricted to the basal-lateral plasma membrane, in duct cells, a broad band of reactivity was located in the apical part of the cell.
These findings suggest a secondary active secretion of phosphate into the primary saliva. Ductal cells appear to be able to reabsorb phosphate, thereby modifying the phosphate concentration in the final saliva.
为阐明人类唾液腺分泌磷酸盐的细胞和分子机制，研究了钠-磷酸盐共转运蛋白的表达及细胞内分布。
从33份腮腺（PG）和35份下颌下腺（SMG）样本中提取总RNA，使用针对所有已知钠-磷酸盐共转运蛋白的基因特异性引物进行逆转录-聚合酶链反应（RT-PCR）。制备了针对NPT2b表位的抗体，并通过免疫组织化学研究细胞和细胞内分布。
未发现I型共转运蛋白NPT1的mRNA。在II型磷酸盐共转运蛋白中，仅在大约相同数量的样本中检测到NPT2b的信息，而未检测到NPT2a或NPT2c的信息（PG中为76%，SMG中为69%）。在两种腺体中也发现了III型共转运蛋白mRNA，PIT1在93%的PG样本中呈阳性结果，而在SMG样本中为69%。对于PIT2，PG中的表达也高于SMG，尽管差异较小（79%对51%）。在腺泡和导管中均发现了NPT2b的免疫染色，后者的反应更强。在腺泡细胞中，NPT2b局限于基底外侧质膜，在导管细胞中，一条较宽的反应带位于细胞顶端部分。
这些发现提示磷酸盐以继发性主动分泌方式进入初始唾液。导管细胞似乎能够重吸收磷酸盐，从而改变最终唾液中的磷酸盐浓度。
