Epidermal Growth Factor and Human Growth Hormone Induce Two Sodium‐Dependent Arginine Transport Systems After Massive Enterectomy

Background: A combination of epidermal growth factor (EGF) and human growth hormone (hGH) after massive enterectomy induces a 400% increase in arginine transport in the remnant distal small intestine. The kinetic mechanism (s) responsible for enhanced arginine transport under these conditions is unknown. Methods: New Zealand White rabbits underwent 70% midjejunoileal resection. After a 1‐week recovery period, animals received hGH (0.2 mg/kg/d IM), EGF (1.5 μg/kg/h SC), hGH + EGF, or vehicle (equal volume) for 7 days. Transport of tritiated arginine into brush border membrane vesicles prepared from distal remnant small intestinal mucosa was quantified in the presence and absence of a sodium gradient over a range of arginine concentrations (25 to 5000 μmol/L). Results: Eadie‐Hofstee transformation of the kinetic data demonstrates two sodium‐dependent arginine transport systems, comprising a high‐capacity, low‐affinity system and a low‐capacity, high‐affinity system. A combination of EGF and hGH significantly upregulates both the high‐capacity (685%) and low‐capacity (350%) maximum transport velocity (V max ). Additionally, EGF alone significantly upregulates V max by 200% in the low‐capacity system. There were no significant changes in transport affinity (K m ) in either system. Conclusions: There are two quiescent sodium‐dependent arginine transport systems in the distal small intestine. A combination of EGF and hGH after massive enterectomy increase arginine transport by V max upregulation in both the high‐capacity/low‐affinity and lowcapacity/high‐affinity systems. (Journal of Parenteral and Enteral Nutrition 22: 326–330, 1998)