Intestinal Na+/H+ exchanger activity is up-regulated by bowel resection in the weanling rat.
Increased Na+/H+ exchanger activity is associated with cellular hyperplasia. Cellular hyperplasia is an adaptive response to small-intestinal resection. Therefore, we hypothesized that the small-intestinal Na+/H+ exchanger activity increases in response to small-intestinal resection. Twenty-one-d-old, male Sprague-Dawley rats were randomly divided to receive either a 70% small intestinal resection (n = 59), or a mid-small intestinal transection (n = 49). Seven d postoperatively, the animals were killed and the Na+/H+ exchanger activity of the intestinal remnants was studied by a well validated brush border membrane vesicle technique. The initial rate of Na+ uptake in the presence of an outwardly directed pH gradient and the Vmax of the amiloride-sensitive Na+ uptake were significantly increased (p < 0.01 and p < 0.001, respectively) in the resection as compared with the transection remnants and to a greater magnitude in the distal as compared with the proximal remnants. Km values were not significantly different. The amiloride-sensitive Na+ uptake in the setting of various intravesicular pH was significantly greater (p < 0.001) in the distal resection as compared with the distal transection remnants, with points of enhanced Na+/H+ exchanger activity of intravesicular pH 6.62 and 6.87, respectively. The presence and activation of the Na+/H+ exchanger's internal modifier site was confirmed by demonstrating the effect of intravesicular pH on Na+ efflux. The present study demonstrates an up-regulation of intestinal Na+/H+ exchange activity in a small-bowel resection model in the weanling rat.(ABSTRACT TRUNCATED AT 250 WORDS)
Vanderbilt University School of Medicine, Department of Pediatrics and Molecular Physiology, Nashville, Tennessee 37232.
A I
AI
Sacks
S A
SA
Acra
W
W
Dykes
D B
DB
Polk
J A
JA
Barnard
J
J
Pietsch
F K
FK
Ghishan
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006965:Hyperplasia; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D017136:Ion Transport; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers; D015854:Up-Regulation
D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride