Active transport of calcium by intestine: effects of dietary calcium

1961 ◽  
Vol 200 (6) ◽  
pp. 1256-1262 ◽  
Author(s):  
Daniel V. Kimberg ◽  
David Schachter ◽  
Harris Schenker
Keyword(s):  
Vitamin D ◽  
Small Intestine ◽  
Active Transport ◽  
Adaptive Response ◽  
Transport Mechanism ◽  
Concentration Gradients ◽  
Active Transport Mechanism ◽  
Entire Small Intestine ◽  
Young Rat

The small intestine of the rat responds facultatively to a diet low in Ca by increasing the active transport of the cation. The effects of calcium deprivation were studied with everted gut sacs and with duodenal slices in vitro, and the experiments demonstrate that following this stimulus almost the entire small intestine of a young rat can transfer calcium from the mucosa to the serosa against concentration gradients. The active transport is maximal in duodenum, less in ileum, and least in the mid small intestine. Following the low-Ca diet, duodenal gut sacs transport Sr89 against concentration gradients, although strontium is transferred much less readily than is calcium. Vitamin D is required for the adaptive response of the active transport in duodenum and ileum. Younger rats respond to Ca deprivation earlier and more markedly than older animals. Neither thyroparathyroidectomy, hypophysectomy, or adrenalectomy prevent response to the low-Ca diet, although these ablations do affect the active transport mechanism in rats on a given diet.

Active transport of Ca45 by the small intestine and its dependence on vitamin D

1959 ◽  
Vol 196 (2) ◽  
pp. 357-362 ◽  
Author(s):  
David Schachter ◽  
Samuel M. Rosen
Keyword(s):  
Vitamin D ◽  
Small Intestine ◽  
Active Transport ◽  
Transport Mechanism ◽  
Calcium Citrate ◽  
Concentration Gradients ◽  
Citrate Complex ◽  
Active Transport Mechanism ◽  
Proximal Small Intestine

Everted gut-sacs prepared from segments of the proximal small intestine of young rabbits, rats and guinea pigs transport Ca45 in vitro from the mucosal to the serosal surfaces against concentration gradients. The active transport mechanism is limited in capacity, is dependent on oxidative phosphorylation, and appears to be relatively specific for Ca++ and Mg++ in contrast to Sr++ and Ba++. Vitamin D deprivation in rabbits and rats markedly impairs the capacity for active Ca45 transport in vitro. The vitamin thus has an effect directly on the upper small intestine. Neither the active Ca45 transport nor the effect of vitamin D on the transport can be explained by an accumulation of citrate and the formation of the calcium-citrate complex.

Active transport of Fe59 by everted segments of rat duodenum

1960 ◽  
Vol 198 (3) ◽  
pp. 609-613 ◽  
Author(s):  
Eugene B. Dowdle ◽  
David Schachter ◽  
Harris Schenker
Keyword(s):  
Small Intestine ◽  
Active Transport ◽  
Transport Process ◽  
Transport Mechanism ◽  
Concentration Gradients ◽  
Active Transport Mechanism ◽  
Proximal Small Intestine ◽  
Rat Duodenum ◽  
Active Transport Process

Everted gut sacs prepared from segments of the proximal small intestine of rats transport Fe59 from the mucosal to the serosal surfaces against concentration gradients in vitro. The active transport mechanism is dependent upon oxidative metabolism and the generation of phosphate-bond energy, and is limited in capacity. The active transport process is maximal in the region of the small intestine immediately distal to the pylorus and diminishes with more distal segments of the gut. Addition of ascorbic acid to the incubation medium markedly increases the active transport of Fe59 in vitro.

Active transport of calcium by the small intestine of the rat

1960 ◽  
Vol 198 (2) ◽  
pp. 263-268 ◽  
Author(s):  
David Schachter ◽  
Eugene B. Dowdle ◽  
Harris Schenker
Keyword(s):  
Small Intestine ◽  
Active Transport ◽  
Transport Mechanism ◽  
Cation Transport ◽  
Maximal Rate ◽  
Active Transport Mechanism ◽  
Serosal Surface ◽  
Proximal Small Intestine ◽  
Active Transfer

The rates of active transport of calcium in vitro by everted gut-sacs prepared from the proximal small intestine of the rat have been quantified and expressed in absolute units. A maximal rate of transport has been measured. The bulk of the calcium transferred to the serosal surface of the gut-sac is ionized calcium, suggesting that the process is an active cation transport mechanism. The active transfer is relatively specific for Ca++, and no significant accumulation of Mg++, Sr++, Ba++ or K+ in the fluid bathing the serosal surface could be demonstrated. The active transport of calcium in vitro is greater with gut-sacs from growing than from older rats, and it is greater with gut-sacs from pregnant than from nonpregnant rats. The results suggest that the active transport mechanism can increase the intestinal absorption of calcium facultatively to meet the needs of the organism.

The Influx of Uric Acid and other Purines into Everted Jejunal Sacs of the Rat and Hamster

1975 ◽  
Vol 53 (1) ◽  
pp. 113-119 ◽  
Author(s):  
A. H. Khan ◽  
S. Wilson ◽  
J. C. Crawhall
Keyword(s):  
Uric Acid ◽  
Active Transport ◽  
Concentration Gradient ◽  
Incubation Medium ◽  
Transport Mechanism ◽  
Concentration Gradients ◽  
Bicarbonate Buffer ◽  
Active Transport Mechanism ◽  
Everted Jejunal Sacs

The in vitro transport of [2-14C]uric acid, [8-14C]hypoxanthine, and [8-14C]xanthine, each dissolved in Krebs–Ringer bicarbonate buffer, was studied with everted jejunal sacs from rat and hamster. No evidence could be obtained for the development of a concentration gradient between the intracellular fluid and the incubation medium or between the sac contents and the incubation medium, for any of the three oxypurines. Inhibitors of active transport, such as anaerobiosis or dinitrophenol, had no significant effect on the rate of transport. A large percentage of hypoxanthine and xanthine was oxidized to uric acid in the sac-wall homogenate, sac contents, and incubation medium during the course of the incubation. This oxidation could be prevented by addition of allopurinol (3 mM) to the incubation medium, but concentration gradients were still not obtained. No active transport mechanism could be demonstrated for uric acid, hypoxanthine, or xanthine in rat or hamster jejunum.

Active transport of calcium by intestine: action and bio-assay of vitamin D

1961 ◽  
Vol 200 (6) ◽  
pp. 1263-1271 ◽  
Author(s):  
David Schachter ◽  
Daniel V. Kimberg ◽  
Harris Schenker
Keyword(s):  
Vitamin D ◽  
Active Transport ◽  
Calcium Transport ◽  
Transport Mechanism ◽  
Simple Diffusion ◽  
Active Mechanism ◽  
Active Transport Mechanism ◽  
Small Doses ◽  
Bio Assay

Vitamin D is required for the active transport of calcium in vitro. Small doses of vitamins D2 and D3 restore the mechanism in depleted rats, and this provides a sensitive bio-assay for the vitamin, independent of an antirachitic effect. Vitamin D influences calcium transfer in all segments of the small intestine, and maximal increments are observed in the duodenum. The effect of vitamin D requires oxidative metabolism in vitro, is maximal where active transport is maximal, and the sterol increases the maximal rates of active transport of calcium. Consequently, vitamin D influences calcium transport by affecting primarily the active mechanism rather than by simple diffusion. Experiments with various monosaccharides demonstrate that two distinct steps are involved in the active transport mechanism in duodenum. Vitamin D is required for both of the steps.

Active transport of iron by intestine: effects of oral iron and pregnancy

1962 ◽  
Vol 203 (1) ◽  
pp. 81-86 ◽  
Author(s):  
James G. Manis ◽  
David Schachter
Keyword(s):  
Single Dose ◽  
Active Transport ◽  
Transport Mechanism ◽  
Iron Absorption ◽  
Late Pregnancy ◽  
Cellular Processes ◽  
Active Transport Mechanism ◽  
Mucosal Uptake

The active transport of iron has been studied further with everted gut sacs and loops of duodenum in the rat. The two-step absorptive mechanism appears to be one of the cellular processes which regulates iron absorption. A single dose of iron by mouth decreases both the net mucosal uptake and the net serosal transfer of iron, as studied with gut sacs in vitro. As little as 0.1 mg Fe is effective; the inhibition observed with 4.0 mg Fe persisted for approximately 17 hr. The reduction in transport appears to result, in part at least, from a direct effect of Fe on the intestine. The active transport mechanism also responds adaptively to the level of Fe in the diet. Late pregnancy increases the Fe transport, as observed with gut sacs in vitro and duodenal loops in vivo, and the effect is primarily on the serosal transfer step.

Transfer of Ca45 across intestinal wall in vitro in relation to action of vitamin D and cortisol

1960 ◽  
Vol 199 (2) ◽  
pp. 265-271 ◽  
Author(s):  
Harold E. Harrison ◽  
Helen C. Harrison
Keyword(s):  
Vitamin D ◽  
Small Intestine ◽  
Active Transport ◽  
Oxidative Metabolism ◽  
Calcium Transport ◽  
Proximal Part ◽  
Intestinal Wall ◽  
The Other ◽  
Cell Surfaces

The transfer of calcium across the intestinal wall of rats was measured in vitro by the device of everted intestinal loops with Ca45 as an indicator. The conditions were developed so that the rate of diffusion of calcium across the intestinal wall as well as active transport against a concentration gradient could be determined. Vitamin D treatment increases the rate of diffusion of calcium across the intestinal wall. This action of vitamin D is exerted along the entire length of the small intestine and is not affected by inhibition of oxidative metabolism. The active transport of calcium on the other hand is localized to the proximal part of the intestine and is dependent on the energy of oxidative metabolism. Cortisol treatment antagonizes the vitamin D effect on the diffusion of calcium and also reduces the active transport of calcium. It is suggested that vitamin D and cortisol influence calcium transport by action on the permeability of cell surfaces to calcium.

In vitro absorption of bile salts by small intestine of rats and guinea pigs

1961 ◽  
Vol 200 (2) ◽  
pp. 313-317 ◽  
Author(s):  
Leon Lack ◽  
I. M. Weiner
Keyword(s):  
Small Intestine ◽  
Bile Acid ◽  
Active Transport ◽  
Sodium Azide ◽  
Concentration Gradient ◽  
Guinea Pigs ◽  
Bile Salts ◽  
Ileal Segment

The transport of taurocholic and glycocholic acids by the small intestine of rats and guinea pigs against a concentration gradient was studied by the everted gutsac technique. Transport of these substances is limited to the distal ileal segment. This transport is inhibited by anoxia, dinitrophenol and sodium azide. The system has a transport maximum. On the basis of these criteria bile acid reabsorption is considered to occur by active transport.

Requirement for vitamin D for the active transport of calcium by the intestine

1960 ◽  
Vol 198 (2) ◽  
pp. 269-274 ◽  
Author(s):  
Eugene B. Dowdle ◽  
David Schachter ◽  
Harris Schenker
Keyword(s):  
Vitamin D ◽  
Active Transport ◽  
Dietary Vitamin ◽  
Adaptive Mechanism ◽  
Low Calcium Diet ◽  
Active Transfer ◽  
In Vitro Maintenance ◽  
Dietary Vitamin D ◽  
Intact Rats

The active transport of calcium from the mucosal to the serosal surfaces of everted gut-sacs of the rat is dependent on the dietary vitamin D. The active transfer in vitro is significantly increased one hour following the administration of calciferol by gastric tube to rats depleted of the vitamin. Vitamins D2 and D3 are approximately equally effective, whereas dihydrotachysterol (A.T. 10) is somewhat more effective than either of the vitamins D. Ultraviolet irradiation of intact rats also increases the active transport of calcium in vitro. Maintenance on a low calcium diet increases the active transfer, whereas thyroparathyroidectomy decreases it. Vitamin D is required to demonstrate both of these effects clearly. The results support the hypothesis that the active transfer is an adaptive mechanism which ensures adequate absorption when the requirement for calcium is increased, or when the diet is low in calcium.

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