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 microg/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 micromol/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 (Vmax). Additionally, EGF alone significantly upregulates Vmax by 200% in the low-capacity system. There were no significant changes in transport affinity (Km) 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 Vmax upregulation in both the high-capacity/low-affinity and low-capacity/high-affinity systems.
Iannoli
P
P
Department of Surgery, University of Rochester Medical Center, New York 14642-8410, USA.
Miller
J H
JH
Sax
H C
HC
D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001692:Biological Transport; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D019382:Human Growth Hormone / Q000494:pharmacology*; D006801:Humans; D007082:Ileum / Q000601:surgery*; D007413:Intestinal Mucosa / Q000378:metabolism; D007583:Jejunum / Q000601:surgery*; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology*; D014316:Tritium
D014316:Tritium; D019382:Human Growth Hormone; D004815:Epidermal Growth Factor; D001120:Arginine; D012964:Sodium