ISSN:
1432-2013
Keywords:
Intestinal perfusion parameters
;
Adrenalectomy
;
Aldosterone
;
Amiloride
;
Anesthesia
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Functionally isolated segments of rat colon and rectum were perfused in situ in a closed loop system. Rectum was defined as the lower 25–35% of the length of large intestine (cecum excluded). Perfusion conditions were optimized at 0.5 ml·min−1 and 3 cm H2O luminal pressure. Variation of perfusion rate between 0.2 and 2 ml·min−1 did not influence net volume transport (J v n ). Luminal distension following elevation of hydrostatic pressure to 18 cm H2O reversibly increasedJ v n . Under control conditionsJ v n and Na+-transport rates (J Na n ) of colon were 2–3 times higher than those of rectum. In colon transepithelial electrical potential difference ψms was time independent −12 mV (lumen negative) whereas rectal ψms increased with time from −6 mV, reaching a plateau of −67 mV within 6h. Amiloride 10−4 mol·l−1 had no effect on ψms,J v n , andJ Na n in colon but did slightly depress K+-secretion in colon descendens. In contrast, ψms in rectum was dosedependently depressed, being reversed to +7 mV at 10−4 mol·l−1.J v n andJ Na n were decreased by half. Acetazolamide in addition to amiloride lowered the positive post-amiloride rectal ψms by half. Adrenalectomy had no effect on colonic ψms, but abolished ψms of the rectum. A single dose of 40 μg·kg−1 b.w. aldosterone during the experiment restored the typical time course of rectal ψms, but did not affect ψms in colon. It is concluded that aldosterone induces an amiloride-sensitive Na+-pathway only in rectum, but not in colon, and that colon and rectum differ basically in their transport properties, quantitatively as well as qualitatively, as do the kidney distal convoluted tubule and the cortical collecting duct.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00581960
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