| Sodium-dependent phosphate intake is an important path for the phosphate absorption in animal intestine. And its properties were detailed in this study, which is beneficial to determine the proper phosphate level in the feed, to reduce phosphate pollution and to improve the utilization of phosphate. By far, the study on Sodium-dependent phosphate intake of pig has been not engough. For well understanding characters of sodium-dependent phosphate absorption in growing pig, two kind of pig, domestic Yorkshire pig and wild Wu Zhi-shan pig, different from development of figure and skelekon were to be research materials. Mucosa was obtained from six 3-month-age growing Yorkshire pigs and Wu Zhi-shan pigs, which was used to prepare epithelium brush-border membrane vesicles (BBMV). The dependence of Pi uptake on pH and sodium concentration was discussed and kinetics of Na+-dependent Pi uptake into BBMV of both kinds of growing pig were estimated and compared by the measurement of phosphate uptake into BBMV within 15s. For studying the distribution of NaPi-IIb and discovering the main site of phosphate absorption in small intestine, the mRNA and protein level of NaPi-IIb were determined by real-time PCR and immunoblotting, respectively.Results showed that acid pH made a negative effect on both sodium-dependent phosphate uptake and passive diffusion. Phosphate uptake into BBMV was strongly dependent on sodium concentration and at least two sodium ion was transported with each phosphate ion. On the condition of pH7.4, the affinity and maximal transport velocity (Vmax) of BBMV for phosphate in jejunum of Wu Zhi-shan pig were higher than these of Yorkshire pig, but the difference was not significant. No signal of NaPi-IIb protein was detected in duodenum of Wu Zhi-shan pig. The expression of NaPi-IIb mRNA and protein level indicated firstly that phosphate transport system of NaPi-IIb existed mainly in ileum, and least in duodenum.
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