Brush border Mg2+-HCO-3-ATPase, supernatant carbonic anhydrase and other enzyme activities isolated from rat intestinal mucosa: effect of adrenalectomy and aldosterone administration.
The possible role of Mg2+-HCO3-ATPase, carbonic anhydrase and several other enzymes in rat intestinal mucosa as mediators of the action of aldosterone has been examined. The small-intestinal tract was cut into seven segments, 15 cm each in length and the mucosa was scraped off, homogenized in 50 mM D-mannitol-2 mM Tris-HCl buffer (pH 7.1), differentially fractionated and a crude brush border was obtained. The mucosa from the colon and rectum was combined and used as the large-intestinal sample. Five days after the adrenalectomy, activities of brush border Mg2+-HCO3-ATPase and supernatant carbonic anhydrase from the upper small intestine decreased to about 60 and 40% of normal values, respectively. Activities of Na+-K+-ATPase, beta-glycerophosphatase and succinate dehydrogenase were all decreased. Two and 4 h after i.p. injection of aldosterone (40 micrograms/kg) to adrenalectomized rats, all enzyme activities increased except for Na+-K+-ATPase in the upper small intestine. In contrast, Mg2+-HCO-3-ATPase and carbonic anhydrase activities were unchanged 3 h after i.p. injection of dexamethasone (200 micrograms and 1 mg/kg). The activation of both Mg2+-HCO3-ATPase and carbonic anhydrase by a single injection of aldosterone was blocked by pretreatment with cycloheximide (1 mg/kg). These results suggest that aldosterone may induce the synthesis of enzyme proteins in the intestinal mucosa.
D000251:Adenosine Triphosphatases / Q000302:isolation & purification* / Q000502:physiology; D000311:Adrenal Glands / Q000502:physiology*; D000315:Adrenalectomy; D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D002256:Carbonic Anhydrases / Q000302:isolation & purification* / Q000502:physiology; D007413:Intestinal Mucosa / Q000201:enzymology* / Q000648:ultrastructure; D008297:Male; D008871:Microvilli / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains
D000450:Aldosterone; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; C032666:magnesium-bicarbonate ATPase; D002256:Carbonic Anhydrases