Modification in the renal phosphate handling after oral administration of glucose to conscious rats

We studied the modification of tubular reabsorption of phosphate (TRPi) in conscious rats given glucose either intravenously or orally. These rats served as their own controls, and were also compared to rats given vehicle intravenously or orally. 30-min urine collections were performed just before the administration of glucose or vehicle, and 15 and 75 min afterwards. Plasma was sampled at the end of each urine collection. Plasma glucose (PG) increased significantly in rats given glucose either intravenously or orally. Intravenous administration of glucose reduced TRPi slightly but significantly, a result also observed in control rats infused with vehicle. On the other hand, a significant decline in TRPi was noted in rats given oral glucose whether or not they had been fasted for the preceding 24 h, but not in those given oral vehicle. The maximal decrease in TRPi was of the same order of magnitude in both fasted and nonfasted rats given glucose orally, although it was delayed in the latter group and significantly higher than in rats infused with glucose. These results suggest a relationship between some factor secreted concomitantly with the ingestion of glucose and the renal handling of phosphate.