Tatsumi S, Segawa H, Morita K, Haga H, Kouda T, Yamamoto H, Inoue Y, Nii T, Katai K, Taketani Y, Miyamoto K I, Takeda E
Department of Clinical Nutrition, School of Medicine, Tokushima University, Tokushima City, Japan.
Endocrinology. 1998 Apr;139(4):1692-9. doi: 10.1210/endo.139.4.5925.
The extracellular concentration of inorganic phosphate (Pi) is an important determinant of parathyroid cell function. The effects of Pi may be mediated through specific molecules in the parathyroid cell membrane, one candidate molecule for which would be a Na+-dependent Pi cotransporter. A complementary DNA encoding a Na+-Pi cotransporter, termed rat PiT-1, has now been isolated from rat parathyroid. The 2890-bp complementary DNA encodes a protein of 681 amino acids that shows sequence identities of 97% and 93% with the type III Na+-Pi cotransporters mouse PiT-1 and human PiT-1, respectively. Expression of rat PiT-1 in Xenopus oocytes revealed that it possesses Na+-dependent Pi cotransport activity. PiT-1 messenger RNA (mRNA) is widely distributed in rat tissues and is most abundant in brain, bone, and small intestine. The amount of PiT-1 mRNA in the parathyroid of vitamin D-deficient rats was reduced compared with that in normal animals and increased markedly after administration of 1,25-dihydroxyvitamin D3. Furthermore, the abundance of PiT-1 mRNA in the parathyroid was much greater in rats fed a low-Pi diet than in those fed a high-Pi diet. Thus, rat PiT-1 may contribute to the effects of Pi and vitamin D on parathyroid function.
细胞外无机磷酸盐（Pi）浓度是甲状旁腺细胞功能的重要决定因素。Pi的作用可能通过甲状旁腺细胞膜中的特定分子介导，其中一个候选分子可能是钠依赖性Pi共转运蛋白。现在已从大鼠甲状旁腺中分离出一种编码钠 - Pi共转运蛋白的互补DNA，称为大鼠PiT - 1。这个2890碱基对的互补DNA编码一个681个氨基酸的蛋白质，该蛋白质与III型钠 - Pi共转运蛋白小鼠PiT - 1和人PiT - 1的序列同一性分别为97%和93%。大鼠PiT - 1在非洲爪蟾卵母细胞中的表达表明它具有钠依赖性Pi共转运活性。PiT - 1信使核糖核酸（mRNA）在大鼠组织中广泛分布，在脑、骨和小肠中含量最高。与正常动物相比，维生素D缺乏大鼠甲状旁腺中PiT - 1 mRNA的量减少，给予1,25 - 二羟基维生素D3后明显增加。此外，低磷饮食喂养的大鼠甲状旁腺中PiT - 1 mRNA的丰度比高磷饮食喂养的大鼠高得多。因此，大鼠PiT - 1可能参与Pi和维生素D对甲状旁腺功能的影响。
