Renal solute excretion is important for the homeostasis of various ions. It is widely believed that hormones such as aldosterone, parathyroid hormone, the vitamin D endocrine system, and growth factors are responsible for alterations in renal ion transport in response to increased absorption of enteric solutes. In the cases of sodium, potassium, and phosphorus, moieties produced in the gastrointestinal tract alter renal ion transport when foods that have high concentrations of cognate ions are ingested. The gastrointestinal tract senses the presence of increased luminal concentrations of these ions, presumably via specific "sensors," and responds by releasing effector substances into the intestinal wall and portal circulation. These substances rapidly increase renal excretion or reduce renal tubular reabsorption and thus blunt large increases in the serum concentrations of these ions. The characterization of enteric solute sensors and mediators will greatly advance our understanding of physiologic mechanisms that control solute homeostasis and will allow the development of specific drugs that stimulate or inhibit these pathways.
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