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D Pansu

Publications and source records attributed to D Pansu.

At least 55 records · Page 3Linked to original sources
PubMed1983

Developmental changes in the mechanisms of duodenal calcium transport in the rat.

Duodenal calcium transport was resolved into a saturable and a nonsaturable process by means of an in situ ligated loop procedure applied to Wistar rats at 3, 12, 19, 24, 30, 40, 60, 110, and 150 days of age. All postweaning animals were males that had been placed on a 1.5% calcium, 1.5% phosphorus semisynthetic diet. Duodenal calcium-binding protein (CaBP) levels were determined at all ages. The newborn rat had no saturable transport component and no CaBP. Its nonsaturable component was very high. With increasing age the saturable component and CaBP varied biphasically, increasing steeply until the animals were about 35 days old; thereafter, each decreased to low but detectable values. The nonsaturable component, on the other hand, decreased in near-linear fashion in the first 35 days; in animals beyond that age it remained invariant. The difference in age dependence between the saturable and nonsaturable components may be considered to constitute additional evidence for the existence of the two transport processes. CaBP and the saturable transport process were highly correlated, further proof that both are vitamin D dependent. Histological studies have revealed the presence of many vacuoles in the intestinal cells of the very young rats; these vacuoles were absent in rats older than 35 days. It is suggested that these vacuoles may be implicated in a pinocytosislike nonsaturable transport that is superimposed on the nonsaturable, non-vitamin D-dependent calcium transport found in all enterocytes.

Aging↗
PubMed1983

Duodenal and ileal calcium absorption in the rat and effects of vitamin D.

An in situ ligated loop procedure was applied to dissect transmural calcium transport in the intestine into two components, a saturable and a nonsaturable process. The existence of two such processes was confirmed in the duodenum, but ileal calcium transport was devoid of the saturable component. There was a small saturable component in the upper jejunum. The level of CaBP, the vitamin D-dependent cytosolic calcium-binding protein (Mr, approximately or equal to 9,000), corresponded to the magnitude of the saturable component. No CaBP was detected in the ileum. Vitamin D dependence of the saturable component was established by inducing it in the duodenum of vitamin D-deficient animals following intraperitoneal injection of 1,25-dihydroxyvitamin D3. In these same animals, conversely, the ileum did not respond to exogenous 1,25-dihydroxyvitamin D3. This confirms the absence in the ileum of the saturable component of transmural calcium movement and the fact that the nonsaturable component is not vitamin D dependent. Everted sac experiments also showed that duodenal sacs from vitamin D-replete or -repleted animals transported calcium against a chemical gradient, whereas ileal sacs did not. Vitamin D regulation of intestinal calcium absorption thus occurs only in the proximal intestine, even though calcium is absorbed down its chemical gradient all along the small intestine.

Animals↗
PubMed1982

Molecular and transport effects of 1,25-dihydroxyvitamin D3 in rat duodenum.

The saturable component of transmural calcium transport in rat duodenum is transcellular, dependent on vitamin D, and can be evaluated by in situ gut loops or everted sacs. Vitamin D action at the molecular level can be studied by analyzing the response in terms of calcium-binding protein (CaBP; Mr congruent to 9000) biosynthesis to exogenous 1,25-dihydroxyvitamin D3 (1,25-(OH)2-D3). In vitamin D-replete animals, the CaBP response occurs within 1 h of intraperitoneal injection when the animals have been fed a high-calcium diet (III), but in 7 h if the animals have been fed a low-calcium diet(I). The latter response appears to be transcriptional, whereas the former seems posttranscriptional. In vitamin D-deficient animals, exogenous 1,25-(OH)2-D3 evokes a CaBP response that occurs 7-8 h after treatment and is transcriptional in nature. Calcium uptake by isolated duodenal cells can be stimulated by prior in vivo treatment with 1,25-(OH)2-D3. Peak response times parallel those found with CaBP biosynthesis, i.e., 3 h in cells from vitamin D-replete animals fed diet III, 7 h in cells from vitamin D-replete animals fed diet I, and 12 h in cells from vitamin D-deficient animal. Cycloheximide treatment appears to inhibit these responses. Moreover, everted sacs from vitamin D-replete animals fed diets III and I show an early and a delayed transport response, respectively. Studies with brush border membrane vesicles prepared from rat duodenum have shown calcium uptake to be vitamin D-dependent. Part of this uptake involves binding to the inner aspect of the membrane and may involve a high-affinity CaBP. Thus a major component of the action of vitamin D in stimulating calcium transport appears to involve protein synthesis. The time and molecular nature of these responses depend on the calcium intake and vitamin D status of the animals. A model of calcium movement through the intestinal cell is included.

Animals↗
PubMed1981

Effect of Ca intake on saturable and nonsaturable components of duodenal Ca transport.

Calcium absorption was studied by an in situ ligated-loop procedure in 9-wk-old male Wistar rats that had been placed from weaning on one of three semisynthetic regimens, 0.17% Ca, 0.44% Ca, or 0.44% Ca plus lactose. Lactose was added because it is known to increase intestinal calcium retention. When the amount of calcium absorbed was expressed as a function of calcium instilled in the loop, it became possible to describe absorption as the sum of a hyperbolic and a linear function, equivalent to a saturable and a nonsaturable process, respectively. The slope of the nonsaturable component was independent of prior calcium intake, while the maximum saturable flux (Jmax) decreased as calcium intake increased. Analysis of the duodenal content of the vitamin D-dependent calcium-binding protein (CaBP, Mr congruent to 10(4)) revealed a positive relation between Jmax and CaBP. Thus, vitamin D appears to be implicated in the saturable, but not in the nonsaturable, component of calcium absorption.

Animals↗
PubMed1981

Sorbin, a peptide contained in porcine upper small intestine which induces the absorption of water and sodium in the rat duodenum.

A fraction increasing water and sodium absorption in rat duodenum was detected in the material obtained at an early stage of purification of the hitherto isolated duodenal hormones. In Wistar rats, duodenal loops were made in situ and filled with a solution containing 0.138 mM NaCl, with 14C PEG and 22Na as markers; the final content was collected after 1 h and the movements of water and Na measured. In contrast to secretin, cholecystokinin, and somatostatin, which induced duodenal secretion, and with pentagastrin, which induced duodenal absorption and stimulated acid secretion, this fraction induced duodenal absorption f Na and water without stimulating acid secretion. The fraction was obtained by chromatography of a concentrate of intestinal peptides in 0.2 M acetic acid on Sephadex G25 (fine), and its active component was found to be methanol-soluble at pH4 and insoluble at pH7.5. It was eluted from carboxymethylcellulose 22 with 0.04 M ammonium bicarbonate and gel filtration of Sephadex G50 *fine), resulting in a tenfold increase in activity. Incubation with chymotrypsin suppressed the biological activity, indicating a peptidic nature. The substance displayed biological and radioimmunological properties distinct from those of the gastrointestinal hormones. Particularly, no cross-reactivity was found with gastrin, prolactin, and angiotensin, which are known to increase intestinal absorption. It therefore seems possible that the activity described is due to a peptide that has as yet not been isolated. The name 'sorbin' is proposed for this active principle.

Animals↗
PubMed1980

Effect of pentagastrin, secretin and cholecystokinin on intestinal water and sodium absorption in the rat.

To test the effect of pentagastrin, secretin and cholecystokinin on intestinal absorption of water and sodium, duodenal , jejunal and ileal loops were prepared in situ in fasted rats, filled with NaCl solution containing 14C PEG and 22Na as markers. Hormones were given by intracardiac injection, the content of the loops was collected 1 h later. In control rats, water and sodium absorption were 5, 30 and 50% of the injected quantities in duodenum, jejunum and ileum, respectively. Pentagastrin (ICI; 1.25, 5 and 20 microgram/100 g) increased the duodenal absorption of water and sodium and decreased the ileal absorption. Secretin (GIH; 0.17, 0.85 AND 3.5 CU/100 g) induced a duodenal secretion and decreased the ileal absorption. Cholecystokinin (GIH; 1, 4, 8 AND 12 IDU) induced a duodenal secretion and decreased the ileal absorption at the lowest dose while the effect disappeared with higher doses. As previously known, the gastrointestinal hormones modulate intestinal absorption of water and sodium. This study indicates that the effect depends on dose and segment under study.

Animals↗
PubMed1979

Effect of lactose on duodenal calcium-binding protein and calcium absorption.

Rats were fed a purified diet containing 30% lactose and calcium absorption was measured in duodenal loops in situ following instillation of 1.25 or 10 mM CaCl2 solutions. Lactose feeding caused absorption to be depressed from 88 to 69% (1.25 mM Ca solution) and from 71 to 43% (10 mM Ca solution). The effect of lactose feeding was more pronounced in 5-month old rats than in 2-month old rats. In the lactose-fed rats, calcium-binding protein (CaBP), measured by a competitive binding assay following partial purification, was depressed on the average from 24 to 10 nmoles Ca bound per mg protein. The effect of the lactose ingestion can be likened to the effect expected from continued high calcium intake, i.e., a decrease in the efficiency of calcium absorption and a decrease in CaBP.

Aging↗
PubMed1977

[Regulation of cell renewal in the gastrointestinal mucosa (author's transl)].

The renewal of the digestive mucosa is the most efficient process assuming the maintenance of the gastrointestinal barrier. The mucous and absorptive cells, born in the proliferative zone, are migrating to the surface and they extrude duirng meals, living 4 to 6 days. Hyperphagia, pregnancy, lactation and intestinal resection induce a hypertrophic state. Fasting, ageing, germ free status provoke a hypoplasia. The ulcerogenic and antimitotic drugs decrease the proliferative activity. The gastrointestinal cell renewal is controlled by hormonal, vitaminic and nervous agents. Gastrin and growth hormone are the major trophic factors, secretom amd cprtocpsteroids act as antitrophic agents. The vitamins A, D and B12, and the nervous transmittors participate in the feed back control assuming a steady state between proliferation and extrusion. Chalones and immunologic factors are probably the most important but unknown inhibitors. The pathological events concerned with abnormal renewal are peptic ulcer, atrophic gastritis, intestinal villous atrophy and digestive cancer.

Animals↗