Active calcium transport by intestinal endoplasmic reticulum during maturation

Arab, Noushin

doi:10.1152/ajpgi.1988.254.1.g74

Cited by 4 publications

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“…The specific activities of enzyme markers in intestinal endoplasmic reticulum membrane vesicles and crude homogenate of epithelial cells from rats at all age groups, showed that NADPH-cytochrome-C-reductase activity was enriched 4.6 times whereas Na+-K+-ATPase, leucine aminopeptidase, cytochrome-C-oxidase, and galactosyl-transferase activities, markers for basolateral, brush border, mitochondrial, and Golgi membranes were impoverished (8). Electronmicroscopic examination of the endoplasmic reticulum vesicles showed sealed vesicles without contamination with either subcellular organelles.…”

Section: Methodsmentioning

confidence: 99%

“…Uptake of phosphate was measured by a rapid filtration technique (13) as used previously in our laboratory (6)(7)(8). Briefly, vesicles obtained in the 100,000 x g centrifugation were preincubated in a solution containing 120 mM KCl, 5 mM MgC12, and 10 mM Hepes/Tris buffer, pH 7.2.…”

Section: Methodsmentioning

confidence: 99%

“…Jejunal phosphate transport take place against an electrochemical gradient and is inhibited by arsenate (1)(2)(3)(4)(5)(6)(7)(8). The uptake of phosphate at the brush border membrane consists of two components: a saturable, electroneutral sodium dependent component and an unsaturable, sodium-independent component (1, 2).…”

mentioning

confidence: 99%

“…The transcellular movement of phosphate is unknown. Recently, we described an important role for the endoplasmic reticulum in transcellular calcium transport (8). This process is ATP dependent and exhibits characteristic devel-opmental patterns (8).…”

mentioning

confidence: 99%

“…Recently, we described an important role for the endoplasmic reticulum in transcellular calcium transport (8). This process is ATP dependent and exhibits characteristic devel-opmental patterns (8). Our study was designed to investigate the role of intestinal endoplasmic reticulum in phosphate transport during maturation in the rat.…”

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Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation

Arab

1988

Pediatr Res

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ABSTRAm. The transport of phosphate into jejunal endoplasmic reticulum vesicles isolated from suckling and adolescent rats was investigated using a rapid filtration technique. Intestinal endoplasmic reticulum from both ages were enriched with NADPH cytochrome-C-reductase whereas other markers for brush border, basolateral, mitochondrial, and Golgi apparatus were impoverished. Phosphate uptake represented an energy-dependent process as evident by more than 80% decrease in uptake values at 0" C compared to 25" C. Phosphate uptake was ATP dependent in both age groups, however, mean uptake values were significantly greater in suckling rats compared to adolescent rats. pH optimum for uptake was 7.2. p-Chloromercuribenzoate at 100 pM concentration inhibited phosphate uptake by more than 90%. Initial rate of phosphate uptake was linear up to 45 s. Kinetics of phosphate uptake at 30 s showed a K, of 0.7 + 0.1 and 0.15 2 0.1 suckling and adolescent rats, respectively. V,., was 1.5 + 0.5 and 0.14 f 0.01 nmol/mg protein/30 s for both suckling and adolescent rats, respectively. Herein we provide evidence for the first time for the presence of a phosphate carrier in intestinal endoplasmic reticulum of rats. Endoplasmic reticulum of phosphate uptake was significantly greater in suckling rats compared to adolescent rats. This increase in uptake is due to a greater number and activity of phosphate carriers in suckling rats. (Pediatr Res 23: 612-615, 1988)The transport of phosphate across the small intestine of suckling and adult animals occurs by an active process (1-5). Jejunal phosphate transport take place against an electrochemical gradient and is inhibited by arsenate (1-8). The uptake of phosphate at the brush border membrane consists of two components: a saturable, electroneutral sodium dependent component and an unsaturable, sodium-independent component (1, 2). The energy driving the sodium-dependent entry of phosphate into the cell is provided by an extracellular to intracellular Na+ gradient maintained by the Na+-K+-ATPase at the basolateral membrane (5). Both sodium-dependent and -independent brush border phosphate uptake are higher in suckling rats compared to adult rats (6). Phosphate exit at the basolateral membrane of the enterocyte occurs by a camer-mediated process that is sodium dependent, electroneutral with stoichiometry of 2 Na:l phosphate at pH 7.4 (7). The transcellular movement of phosphate is unknown. Recently, we described an important role for the endoplasmic reticulum in transcellular calcium transport (8). This process is ATP dependent and exhibits characteristic devel- opmental patterns (8). Our study was designed to investigate the role of intestinal endoplasmic reticulum in phosphate transport during maturation in the rat. We used a millipore filtration system to study phosphate uptake by intestinal microsomes. EXPERIMENTAL PROCEDURES Isolation of intestinal endoplasmic reticulum vesicles.The jejunum of two adolescent rats (42 + 2 days) of 12 suckling rats (14 + 1 day) were used to prepare the en...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation

Arab

1988

Pediatr Res

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The effect of hydrocortisone and thyroxine on development of calcium homeostasis in embryonic intestinal epithelium

Rogers

Black

1996

Experientia

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Cytoplasmic Ca2+ concentration of epithelial cells from 14-day embryonic chick duodena decreased during 72 h of organ culture to a value 54% of that found at 17 days in vivo. The ability of cells to maintain a constant Ca2+ concentration when challenged with high extracellular calcium was also significantly reduced. Addition of 1 microM hydrocortisone during culture restored both parameters of Ca2+ homeostasis to that of 16-day uncultured duodena, and rise in cytoplasmic Ca2+ was significant within 4 h of hormone treatment. Thyroxine influenced epithelial Ca2+ similarly, but to a lesser degree and only after 48-72 h of culture. These data indicate that glucocorticoids, and possibly thyroid hormones, influence the development of calcium homeostasis in intestinal epithelium.

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Differences in Ca²⁺ signaling underlie age-specific effects of secretagogues on colonic Cl⁻transport

Venkatasubramanian¹,

Selvaraj²,

Carlos

et al. 2001

American Journal of Physiology-Cell Physiology

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Taurodeoxycholic acid (TDC) stimulates Cl(-) transport in adult (AD), but not weanling (WN) and newborn (NB), rabbit colonic epithelial cells (colonocytes). The present study demonstrates that stimuli like neurotensin (NT) are also age specific and identifies the age-dependent signaling step. Bile acid actions are segment and bile acid specific. Thus although TDC and taurochenodeoxycholate stimulate Cl(-) transport in AD distal but not proximal colon, taurocholate has no effect in either segment. TDC increases intracellular Ca(2+) concentration ([Ca(2+)](i)) in AD, but not in WN and NB, colonocytes. In AD cells, TDC (5 min) action on Cl(-) transport needs intra- but not extracellular Ca(2+). NT, histamine, and bethanechol increase Cl(-) transport and [Ca(2+)](i) in AD, but not WN, distal colonocytes. However, A-23187 increased [Ca(2+)](i) and Cl(-) transport in all age groups, suggesting that Ca(2+)-sensitive Cl(-) transport is present from birth. Study of the proximal steps in Ca(2+) signaling revealed that NT, but not TDC, activates a GTP-binding protein, Galpha(q), in AD and WN cells. In addition, although WN and AD colonocytes had similar levels of phosphatidylinositol 4,5-bisphosphate, NT and TDC increased 1,4,5-inositol trisphosphate content only in AD cells. Nonresponsiveness of WN cells to Ca(2+)-dependent stimuli, therefore, is due to the absence of measurable phospholipase C activity. Thus delays in Ca(2+) signaling afford a crucial protective mechanism to meet the changing demands of the developing colon.

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Active calcium transport by intestinal endoplasmic reticulum during maturation

Cited by 4 publications

References 0 publications

Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation

Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation

The effect of hydrocortisone and thyroxine on development of calcium homeostasis in embryonic intestinal epithelium

Differences in Ca²⁺ signaling underlie age-specific effects of secretagogues on colonic Cl⁻transport

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Active calcium transport by intestinal endoplasmic reticulum during maturation

Cited by 4 publications

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Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation

Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation

The effect of hydrocortisone and thyroxine on development of calcium homeostasis in embryonic intestinal epithelium

Differences in Ca2+ signaling underlie age-specific effects of secretagogues on colonic Cl−transport

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Differences in Ca²⁺ signaling underlie age-specific effects of secretagogues on colonic Cl⁻transport