al-Mahrouq H A, Kempson S A
Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46202-5120.
Biochim Biophys Acta. 1992 Feb 17;1104(1):83-6. doi: 10.1016/0005-2736(92)90134-8.
In an attempt to identify the renal Na+/Pi cotransporter, Xenopus laevis oocytes were used to express mRNA isolated from the renal cortex of rat kidney. Na(+)-dependent uptake of Pi in oocytes, injected with mRNA, resulted in an increase of 2-4-fold as compared to oocytes injected with water. Both the new expressed and endogenous Na(+)-dependent Pi uptake activity were inhibited with 2 mM phosphonoformic acid (PFA). Expression of Pi uptake into oocytes was dose-dependent with the amount of mRNA injected. When mRNA was fractionated on a sucrose gradient, a mRNA fraction of 2.5 kilobases expressed the Na+/Pi cotransport activity in oocytes. This fraction resulted in a 6-fold stimulation of Na(+)-dependent Pi transport when compared to oocytes injected with water. The Km and Vmax for Na(+)-dependent Pi uptake were 0.18 mM and 118 pmol/oocyte per 30 min, respectively.
为了鉴定肾脏的钠/磷酸根共转运体，非洲爪蟾卵母细胞被用于表达从大鼠肾脏皮质分离的mRNA。注射了mRNA的卵母细胞中，磷酸根的钠依赖性摄取相较于注射水的卵母细胞增加了2至4倍。新表达的和内源性的钠依赖性磷酸根摄取活性均被2 mM膦甲酸（PFA）抑制。卵母细胞中磷酸根摄取的表达与注射的mRNA量呈剂量依赖性。当mRNA在蔗糖梯度上分级分离时，一个2.5千碱基的mRNA组分在卵母细胞中表达了钠/磷酸根共转运活性。与注射水的卵母细胞相比，该组分导致钠依赖性磷酸根转运增加了6倍。钠依赖性磷酸根摄取的Km和Vmax分别为0.18 mM和每30分钟118 pmol/卵母细胞。
