Influence Of Hexoses On Intestinal Phosphate Transport Using Everted Gut Sacs Of Mice

Background & objectives: Active transports of intestinal glucose and phosphate (Pi) is shown to be sodium dependent. Earlier reports show an inhibitory role for glucose on intestinal Pi transport . Information on other hexoses is scanty. So this study is conducted to see the effects of hexoses like galactose , 3-O-methyl glucose and fructose on phosphate transport. Materials and methods: Everted gut sacs from proximal intestine were prepared from Swiss male albino mice. The sacs were filled with 0. 5ml of serosal fluid and placed in mucosal medium of same composition. After incubation of an hour, the amount of Pi lost from mucosal medium and serosal gain of phosphate are estimated. To test the effect of hexoses on Pi transport sugars were added (5.5mM) to the incubation medium (fructose 5.5 and 10mM).To evaluate the inhibitory role of fructose on Pi transport , Succinate and fumerate were added to the serosal compartment. Moreover intraperitoneal injection of mannoheptulose (MH) was given to mice 30 minutes prior to experimentation to load the tissue with MH. Results: Pi uptake from brush border is reduced significantly by glucose, galactose and 3-0-methyl glucose but not by fructose. Fructose significantly attenuated Pi release process. Fumarate, succinate and preloading with MH lifted this inhibitory effect of fructose partly but significantly (significance p<0.001). Conclusion: Sodium dependent transports of glucose, galactose, 3-O-methyl glucose that are mediated through a common carrier inhibits brush border Pi uptake. Fructose may be transported differently and its phosphorylation in the intestinal wall may be causing inhibition on Pi release. Succinate and fumarate breaks down phosphorylated fructose and action of MH is inexplicable.