Intestinal brush border calcium uptake in spontaneously hypertensive rats and their genetically matched WKY rats

H. Shibata, Fayez K Ghishan

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Abstract

The current studies were designed to characterize calcium transport by intestinal brush border membrane in the spontaneously hypertensive rat (SHR) and normotensive control, the Wistar-Kyoto (WKY) rat. The biochemical and functional purity of the intestinal brush border membranes in SHR and WKY rats was validated by marker enzymes and the ability to transiently transport D-glucose in the presence of Na+ gradient. Calcium transport into duodenal and jejunal vesicles represented a minor binding component and transmembrane movement as evident by initial rate studies, A23187 studies, and lanthanum displacement experiments. Initial rate and time course of calcium uptake was lower in SHR compared with WKY rats. Kinetic analysis of calcium uptake by the jejunum (total uptake minus binding component) showed a V(max) of 6.98 ± 0.2 and 1.8 ± 0.2 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.001), whereas K(m) values were 0.76 ± 0.04 and 0.87 ± 0.1 mM for WKY rats and SHR, respectively. Similar kinetic analysis of calcium uptake by the duodenal segments showed a V(max) of 10.3 ± 0.8 and 2.8 ± 0.2 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.01). K(m) values were 0.7 ± 0.2 and 0.3 ± 0.06 mM (P > 0.05). V(max) of calcium uptake in the 2-week-old rats (prehypertensive period) was 6.0 ± 0.3 and 3.53 ± 0.3 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.001), whereas K(m) values were 0.60 ± 0.07 and 0.5 ± 0.01 mM, respectively. These results suggest that calcium binding and uptake by duodenal and jejunal intestinal brush border membranes of SHR is significantly decreased compared with WKY rats. The decrease in transmembrane calcium uptake is secondary to decrease in V(max) and is present before the appearance of hypertension, implying a genetically determined defect in calcium uptake in intestinal brush border membranes of the SHR.

Original languageEnglish (US)
Pages (from-to)54-60
Number of pages7
JournalProceedings of the Society for Experimental Biology and Medicine
Volume196
Issue number1
StatePublished - 1991
Externally publishedYes

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Inbred WKY Rats
Inbred SHR Rats
Brushes
Microvilli
Rats
Calcium
Membranes
Lanthanum
Calcimycin
Jejunum
Proteins
Hypertension
Glucose
Enzymes

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

Cite this

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title = "Intestinal brush border calcium uptake in spontaneously hypertensive rats and their genetically matched WKY rats",
abstract = "The current studies were designed to characterize calcium transport by intestinal brush border membrane in the spontaneously hypertensive rat (SHR) and normotensive control, the Wistar-Kyoto (WKY) rat. The biochemical and functional purity of the intestinal brush border membranes in SHR and WKY rats was validated by marker enzymes and the ability to transiently transport D-glucose in the presence of Na+ gradient. Calcium transport into duodenal and jejunal vesicles represented a minor binding component and transmembrane movement as evident by initial rate studies, A23187 studies, and lanthanum displacement experiments. Initial rate and time course of calcium uptake was lower in SHR compared with WKY rats. Kinetic analysis of calcium uptake by the jejunum (total uptake minus binding component) showed a V(max) of 6.98 ± 0.2 and 1.8 ± 0.2 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.001), whereas K(m) values were 0.76 ± 0.04 and 0.87 ± 0.1 mM for WKY rats and SHR, respectively. Similar kinetic analysis of calcium uptake by the duodenal segments showed a V(max) of 10.3 ± 0.8 and 2.8 ± 0.2 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.01). K(m) values were 0.7 ± 0.2 and 0.3 ± 0.06 mM (P > 0.05). V(max) of calcium uptake in the 2-week-old rats (prehypertensive period) was 6.0 ± 0.3 and 3.53 ± 0.3 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.001), whereas K(m) values were 0.60 ± 0.07 and 0.5 ± 0.01 mM, respectively. These results suggest that calcium binding and uptake by duodenal and jejunal intestinal brush border membranes of SHR is significantly decreased compared with WKY rats. The decrease in transmembrane calcium uptake is secondary to decrease in V(max) and is present before the appearance of hypertension, implying a genetically determined defect in calcium uptake in intestinal brush border membranes of the SHR.",
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AB - The current studies were designed to characterize calcium transport by intestinal brush border membrane in the spontaneously hypertensive rat (SHR) and normotensive control, the Wistar-Kyoto (WKY) rat. The biochemical and functional purity of the intestinal brush border membranes in SHR and WKY rats was validated by marker enzymes and the ability to transiently transport D-glucose in the presence of Na+ gradient. Calcium transport into duodenal and jejunal vesicles represented a minor binding component and transmembrane movement as evident by initial rate studies, A23187 studies, and lanthanum displacement experiments. Initial rate and time course of calcium uptake was lower in SHR compared with WKY rats. Kinetic analysis of calcium uptake by the jejunum (total uptake minus binding component) showed a V(max) of 6.98 ± 0.2 and 1.8 ± 0.2 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.001), whereas K(m) values were 0.76 ± 0.04 and 0.87 ± 0.1 mM for WKY rats and SHR, respectively. Similar kinetic analysis of calcium uptake by the duodenal segments showed a V(max) of 10.3 ± 0.8 and 2.8 ± 0.2 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.01). K(m) values were 0.7 ± 0.2 and 0.3 ± 0.06 mM (P > 0.05). V(max) of calcium uptake in the 2-week-old rats (prehypertensive period) was 6.0 ± 0.3 and 3.53 ± 0.3 nmol/mg protein/7 sec in WKY rats and SHR, respectively (P < 0.001), whereas K(m) values were 0.60 ± 0.07 and 0.5 ± 0.01 mM, respectively. These results suggest that calcium binding and uptake by duodenal and jejunal intestinal brush border membranes of SHR is significantly decreased compared with WKY rats. The decrease in transmembrane calcium uptake is secondary to decrease in V(max) and is present before the appearance of hypertension, implying a genetically determined defect in calcium uptake in intestinal brush border membranes of the SHR.

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