title: Alkaline phosphatase and ATPases in brush-border membranes of rat jejunum: distinct effects of divalent cations and of some inhibitors.
abstract: The effects of divalent cations and of some inhibitors on the activities of alkaline phosphatase and ATPase were examined in rat jejunal brush-border membranes (BBM) isolated by tha Ca(2+)-(BBMCa) or the Mg(2+)-precipitation method (BBMMg). Similar results were found in BBMCa and BBMMg though generally higher in BBMCa. Alkaline phosphatase activity was stimulated by 5 mM MgCl2 (30% to 44%), but not by 5 mM CaCl2 or 0.1 mM ZnCl2, at pH 9.5 or 7.4. ATPase activity was equally stimulated by 5 mM MgCl2 and by 5 mM CaCI2 (about 150%). Alkaline phosphatase activity was significantly inhibited by 1 mM vanadate, 5 mM diamox, 5.0 mM L-leucine and 1 mM theophylline. In contrast, Ca(2+)-ATPase and Mg(2+)-ATPase activities were not depressed by those alkaline phosphatase inhibitors, but were inhibited by 0.1 mM trifluoperazine (more than 70%). 0.1 mM ZnCl2 also appeared to be inhibitory to Ca(2+)-ATPase and Mg(2+)-ATPase, but not to alkaline phosphatase activity even in the presence of Ca2+ and Mg2+. These results suggest that Ca(2+)-ATPase and Mg(2+)-ATPase activities of the rat jejunal BBM are not merely manifestations of alkaline phosphatase, but rather belong to (a) distinct enzyme(s).
authors.affiliation: Laboratory of General and Comparative Biochemistry, University of Liège, Belgium.
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Gilles-Baillien
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002413:Cations, Divalent; D002712:Chlorides / Q000494:pharmacology; D007583:Jejunum / Q000201:enzymology* / Q000648:ultrastructure; D007930:Leucine / Q000494:pharmacology; D015636:Magnesium Chloride / Q000494:pharmacology; D008297:Male; D008871:Microvilli / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar; D013806:Theophylline / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology; D017967:Zinc Compounds
chemical_list: D002413:Cations, Divalent; D002712:Chlorides; D017967:Zinc Compounds; D015636:Magnesium Chloride; D014268:Trifluoperazine; D014638:Vanadates; C016837:zinc chloride; D013806:Theophylline; D000469:Alkaline Phosphatase; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D007930:Leucine; D015032:Zinc; D002122:Calcium Chloride; D000086:Acetazolamide