Abstract：
:The purpose of this study was to investigate whether Ca2+ -Mg2+ ATPase in the distal tubule (where calcium transport is active, against a gradient, and hormone dependent) presents some characteristics different from those observed in the proximal tubule, and whether these characteristics are likely to shed light on the respective roles of this enzyme at the two sites of the nephron. The Ca2+ - and Mg2+-dependent ATP hydrolysis was measured in microdissected segments of the distal nephron, the kinetic parameters were determined, and the influence of magnesium upon the sensitivity to calcium was examined. Results were compared with those obtained in the proximal tubule, and in purified membranes as reported by others. In the distal tubule, low concentrations of Mg2+ (less than 10(-7) M) did not influence ATP hydrolysis. At concentrations above 10(-7) M, Mg2+ increased ATP hydrolysis according to Michaelis kinetics (apparent Km = 11.3 +/- 2.4 microM, Vmax = 219 +/- 26 pmol.mm-1.20 min-1). The addition of 1 microM Ca2+ decreased the apparent Km for Mg2+ and the Vmax for Mg2+. Similar results were obtained in the proximal tubule. At low Mg2+ concentrations, Ca2+ also stimulated ATP hydrolysis according to Michaelis kinetics with an apparent Km value for Ca2+ of 0.18 +/- 0.06 and 0.10 +/- 0.03 microM Ca2+ (ns) and a Vmax of 101 +/- 12 and 89 +/- 9 pmol.mm-1.20 min-1 (ns) in the distal and proximal tubules, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
journal_name
Can J Physiol Pharmacoljournal_title
Canadian journal of physiology and pharmacologyauthors
Brunette MG,Blouin S,Chan Mdoi
10.1139/y87-328subject
Has Abstractpub_date
1987-10-01 00:00:00pages
2093-8issue
10eissn
0008-4212issn
1205-7541journal_volume
65pub_type
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journal_title：Canadian journal of physiology and pharmacology
pub_type： 杂志文章
doi：10.1139/y94-150
更新日期：1994-09-01 00:00:00
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journal_title：Canadian journal of physiology and pharmacology
pub_type： 杂志文章
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更新日期：1995-08-01 00:00:00
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journal_title：Canadian journal of physiology and pharmacology
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journal_title：Canadian journal of physiology and pharmacology
pub_type： 杂志文章
doi：
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journal_title：Canadian journal of physiology and pharmacology
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journal_title：Canadian journal of physiology and pharmacology
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更新日期：1981-10-01 00:00:00
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更新日期：2011-01-01 00:00:00
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journal_title：Canadian journal of physiology and pharmacology
pub_type： 杂志文章
doi：10.1139/y02-141
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journal_title：Canadian journal of physiology and pharmacology
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更新日期：2001-01-01 00:00:00
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更新日期：1991-04-01 00:00:00
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更新日期：2014-06-01 00:00:00
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journal_title：Canadian journal of physiology and pharmacology
pub_type： 杂志文章
doi：10.1139/y89-195
更新日期：1989-10-01 00:00:00
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更新日期：2002-07-01 00:00:00
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pub_type： 杂志文章
doi：10.1139/y08-064
更新日期：2008-09-01 00:00:00
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更新日期：2006-12-01 00:00:00
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更新日期：1991-09-01 00:00:00
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journal_title：Canadian journal of physiology and pharmacology
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更新日期：1985-09-01 00:00:00
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journal_title：Canadian journal of physiology and pharmacology
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doi：
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