Calcium Absorption Across Epithelia

2005 ◽  
Vol 85 (1) ◽  
pp. 373-422 ◽  
Author(s):  
Joost G. J. Hoenderop ◽  
Bernd Nilius ◽  
René J. M. Bindels

Ca2+is an essential ion in all organisms, where it plays a crucial role in processes ranging from the formation and maintenance of the skeleton to the temporal and spatial regulation of neuronal function. The Ca2+balance is maintained by the concerted action of three organ systems, including the gastrointestinal tract, bone, and kidney. An adult ingests on average 1 g Ca2+daily from which 0.35 g is absorbed in the small intestine by a mechanism that is controlled primarily by the calciotropic hormones. To maintain the Ca2+balance, the kidney must excrete the same amount of Ca2+that the small intestine absorbs. This is accomplished by a combination of filtration of Ca2+across the glomeruli and subsequent reabsorption of the filtered Ca2+along the renal tubules. Bone turnover is a continuous process involving both resorption of existing bone and deposition of new bone. The above-mentioned Ca2+fluxes are stimulated by the synergistic actions of active vitamin D (1,25-dihydroxyvitamin D3) and parathyroid hormone. Until recently, the mechanism by which Ca2+enter the absorptive epithelia was unknown. A major breakthrough in completing the molecular details of these pathways was the identification of the epithelial Ca2+channel family consisting of two members: TRPV5 and TRPV6. Functional analysis indicated that these Ca2+channels constitute the rate-limiting step in Ca2+-transporting epithelia. They form the prime target for hormonal control of the active Ca2+flux from the intestinal lumen or urine space to the blood compartment. This review describes the characteristics of epithelial Ca2+transport in general and highlights in particular the distinctive features and the physiological relevance of the new epithelial Ca2+channels accumulating in a comprehensive model for epithelial Ca2+absorption.

1986 ◽  
Vol 113 (1) ◽  
pp. 96-103 ◽  
Author(s):  
Heide S. Cross ◽  
Doris Pölzleitner ◽  
Meinrad Peterlik

Abstract. Thyroxine (T4) and triiodothyronine (T3) activate Na+-dependent inorganic phosphate (Pi) transport in organ-cultured embryonic chick small intestine. Induction of transport activity requires intact protein synthesis and can be expressed in enterocytes with varying degrees of differentiation. T3 and T4 exert their effect independent of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), which is shown to stimulate Pi uptake only in the final stage of embryonic differentiation. At this time point, a potentiating effect of 1,25(OH)2D3 and T4 on Pi transport in cultured jejunum can be demonstrated. Thyroid hormones appear to stimulate Na+ gradient-driven Pi transport without concomitantly raising (Na+-K+)-ATPase activity. T4 has no influence whatsoever on calcium uptake by cultured embryonic small intestine while 1,25(OH)2D3 is effective at all stages of embryonic development investigated (day 15–20). However, when both hormones were present in the culture medium, the effect of 1,25(OH)2D3 on calcium transport is doubled. Our results suggest that the hyperphosphataemia associated with hyperthyroidism is likely to result, at least in part, from the independent effect of thyroid hormones as well as from their potentiation of the 1,25(OH)2D3 action on Na+-dependent intestinal Pi transport. In addition, their permissive effect on 1,25(OH)2D3-induced calcium absorption provides an explanation for unaltered calcium absorption in a number of hyperthyroid patients, although reduced plasma levels of 1,25(OH)2D3 are generally observed in this condition.


Author(s):  
А.А. Коваленко ◽  
Г.П. Титова ◽  
В.К. Хугаева

Оперативное лечение различных заболеваний кишечника сопровождается осложнениями в виде нарушений микроциркуляции в области анастомоза кишки. Ранее нами показана способность лимфостимуляторов пептидной природы восстанавливать нарушенную микроциркуляцию, что послужило основой для настоящего исследования. Цель работы - оценка влияния стимуляции лимфотока в стенке кишки на процессы восстановления микроциркуляции, структуры и функции тонкой кишки в области оперативного вмешательства. Методика. В экспериментах на наркотизированных крысах (хлоралгидрат в дозе 0,6 г/кг в 0,9% растворе NaCl) моделировали различные поражения тонкой кишки (наложение лигатуры, перевязка 1-3 брыжеечных артерий, перекрут петли кишки вокруг оси брыжейки, сочетание нескольких видов повреждений). Резекция поврежденного участка через 1 сут. с последующим созданием тонкокишечного анастомоза завершалась орошением операционного поля раствором пептида-стимулятора лимфотока (40 мкг/кг массы животного в 1 мл 0,9% раствора NaCl). На 7-е сут. после операции проводили гистологическое исследование фрагмента кишки в области анастомоза. Результаты. На 7-е сут. после резекции у выживших животных (летальность вследствие кишечной непроходимости составляла 30%) имеют место морфологические признаки острых сосудистых нарушений стенки кишки, изменений кровеносных и лимфатических микрососудов, интерстициальный отек всех слоев стенки кишки, дилатация просвета кишки, повреждение всасывающего эпителия ворсин с истончением щеточной каемки клеток, морфологические признаки гиперфункции бокаловидных клеток. Использование лимфостимулятора пептидной природы после операции увеличивало выживаемость животных на 24%. У части животных отмечалось уменьшение расширения просвета кишки, у других практически полная его нормализация. Восстанавливалась форма кишечных ворсин и распределение бокаловидных клеток. Отсутствовали признаки внутриклеточного и межмышечного отека. Отмечено умеренное полнокровие венул. Заключение. Использование лимфостимулятора при хирургическом лечении кишечной непроходимости увеличивает выживаемость животных на 24% по сравнению с контролем, способствует более раннему восстановлению структуры и функции тонкой кишки. Полученные результаты свидетельствуют о перспективности использования стимуляции лимфотока при операциях на кишечнике. Surgical treatment of bowel diseases is associated with complications that cause microcirculatory disturbances in the anastomosis area and may lead to a fatal outcome. This study was based on our previous finding that peptide-type lymphatic stimulators are able to restore impaired microcirculation. The aim of this work was stimulating the lymph flow in the intestinal wall to facilitate recovery of microcirculation, structure and function of the small intestine in the area of surgical intervention. Methods. In experiments on anesthetized rats (0.6 g/kg chloral hydrate in 0.9% NaCl), various small bowel lesions were modeled (bowel ligation, ligation of 1-3 mesenteric arteries, gut torsion, combination of several lesion types). In 24 h, the damaged area was resected, and a small intestine anastomosis was creased. The surgery was completed with irrigation of the operative field with a solution of lymph flow stimulating peptide (40 мg/kg body weight in 1 ml of 0.9% NaCl). A gut fragment from the anastomosis area was examined histologically on day 7 after the surgery. Results. On the 7th day after removing the intestinal obstruction, the surviving animals (lethality 30%) had morphological signs of acute vascular disorders in the intestinal wall; changes in blood and lymphatic microvessels; interstitial edema of all intestinal wall layers; dilatation of the intestinal lumen; damage to the absorptive epithelium of villi with thinning of the brush border, and hyperfunction of mucous (goblet) cells. The use of the peptide after surgery increased the survival rate of animals by 24% and provided a smaller dilatation of the intestinal lumen in some animals. In other animals, the lumen recovered. The shape of intestinal villi and distribution of goblet cells were restored. Signs of intracellular and intermuscular edema were absent. Moderate venular congestion was noticed. Conclusion. Using the lymphatic stimulator in surgical treatment of intestinal obstruction increases the survival rate of animals by 24% compared to the control, facilitates earlier restoration of the small intestine structure and function. The obtained results indicated the effectiveness of lymphatic stimulation in intestinal surgery.


2021 ◽  
Vol 14 (5) ◽  
pp. e240226
Author(s):  
Sachin Mohan ◽  
Elliot Graziano ◽  
James Campbell ◽  
Irshad H Jafri

Amyloidosis constitutes a heterogeneous group of disorders of protein misfolding that can involve different organ systems. The disease can occur either in a systemic or localised manner that is well known to involve the gastrointestinal (GI) tract. GI amyloidosis can present with a wide range of symptoms including diarrhoea, bleeding and obstruction. This case illustrates a patient with localised jejunal amyloid light chain disease that was diagnosed serendipitously during a workup for haematuria. Our patient was otherwise asymptomatic, but this case underscores the importance of considering amyloidosis as a possible cause of isolated masses of the small intestine.


2017 ◽  
Vol 45 (7) ◽  
pp. 904-910 ◽  
Author(s):  
Reinhold G. Erben

Fibroblast growth factor-23 (FGF23) is a bone-derived hormone, mainly produced by osteoblasts and osteocytes in response to increased extracellular phosphate and circulating vitamin D hormone. Endocrine FGF23 signaling requires co-expression of the ubiquitously expressed FGF receptor 1 (FGFR1) and the co-receptor α-Klotho (Klotho). In proximal renal tubules, FGF23 suppresses the membrane expression of the sodium–phosphate cotransporters Npt2a and Npt2c which mediate urinary reabsorption of filtered phosphate. In addition, FGF23 suppresses proximal tubular expression of 1α-hydroxylase, the key enzyme responsible for vitamin D hormone production. In distal renal tubules, FGF23 signaling activates with-no-lysine kinase 4, leading to increased renal tubular reabsorption of calcium and sodium. Therefore, FGF23 is not only a phosphaturic but also a calcium- and sodium-conserving hormone, a finding that may have important implications for the pathophysiology of chronic kidney disease. Besides these endocrine, Klotho-dependent functions of FGF23, FGF23 is also an auto-/paracrine suppressor of tissue-nonspecific alkaline phosphatase transcription via Klotho-independent FGFR3 signaling, leading to local inhibition of mineralization through accumulation of pyrophosphate. In addition, FGF23 may target the heart via an FGFR4-mediated Klotho-independent signaling cascade. Taken together, there is emerging evidence that FGF23 is a pleiotropic hormone, linking bone with several other organ systems.


1990 ◽  
Vol 259 (3) ◽  
pp. G443-G452 ◽  
Author(s):  
L. C. Read ◽  
A. P. Lord ◽  
V. Brantl ◽  
G. Koch

beta-Casomorphins (beta-CMs) derived from milk beta-casein may exert various opiate activities in milk-fed infants. To assess the physiological significance of beta-CMs as a source of circulating opioids in infants, we measured absorption rates of several beta-CMs under near-physiological conditions using in situ autoperfused lamb intestine. The naturally occurring beta-CMs, beta-CM-7 and beta-CM-4-amide, were absorbed readily into blood with no transfer into lymph. Uptake peaked within several minutes of the luminal infusion of peptide but then declined sharply and stopped within a further 10-15 min. The recovery in blood, intestinal contents, and tissue at the end of the 30-min experiment was less than 1% of the infused dose. The low recovery was due to rapid proteolysis based on in vitro studies that demonstrated half-lives of less than 5 min in lamb blood, luminal contents, and lymph. The synthetic dipeptidyl peptidase IV-resistant analogue beta-[D-Ala2]CM- 4-amide was stable during incubation in blood, lymph, or luminal contents and was absorbed into blood at rates that were maximal within several minutes and remained steady for the 30-min period. We conclude that although natural beta-CMs are transferred across the lamb small intestine, rapid degradation within the intestinal lumen, gut epithelium, and blood would prevent entry into the circulation under normal conditions. Val-beta-CM-7, a putative stable precursor, had similar stability and kinetics of absorption to beta-CM-7, results that exclude Val-beta-CM-7 as a stable precursor for delivery of beta-CMs to the circulation. Essentially identical results to those in lambs were obtained in 7-day-old piglets.


1968 ◽  
Vol 22 (2) ◽  
pp. 237-246 ◽  
Author(s):  
Aileen M. Lennox ◽  
A. K. Lough ◽  
G. A. Garton

1. Total lipids were extracted from digesta obtained from the rumen, abomasum and upper small intestine (jejunum) of each of four slaughtered sheep. The lipids were fractionated into unesterified fatty acids, neutral lipids and phospholipids and the proportional contribution of each fraction to the total fatty acids was determined.2. The contribution made by phospholipids to the total fatty acids in the digesta showed a marked increase in the samples from the small intestine compared with those from the rumen and abomasum. This increase was apparently due to the presence of biliary phospholipids.3. Total lipids and conjugated bile acids were extracted from sheep bile, the lipids were fractionated and their fatty-acid composition was determined. Phospholipids predominated and these consisted mainly of phosphatidylcholine, together with some lysophosphatidylcholine.4. Both phospholipids contained significant amounts of unsaturated C18 components which could account, at least in part, for the previously reported increament to the proportion of these acids in the digesta when it enters the upper jejunum.5. The overall fatty acid compositions of the two biliary phospholipids were very similar and, in common with other naturally occurring phosphatidylcholines, the fatty acids present in position 2 of the phosphatidylcholine of bile were found to consist almost entirely of unsaturated components.6. Total lipids and conjugated bile acids were extracted from samples of digesta obtained from three sheep with cannulas in different positions in the jejunum. Analysis of the lipids indicated that biliary phospholipids, in particular phosphatidylcholine, underwent progressive hydrolysis in the intestinal lumen.7. The distribution of conjugated bile acids, unesterified fatty acids and phospholipids between the solid (particulate) and liquid (micellar) phases of the intestinal digesta was determined. These chyme constituents were, for the most part, associated with the particulate matter and thus, at any given time, it appears that only a small fraction of the total fatty acids is available for absorption in micellar form. It is suggested that the micellar solubilization of fatty acids may be facilitated by the presence of lysophosphatidylcholine.


2017 ◽  
Vol 114 (38) ◽  
pp. 10178-10183 ◽  
Author(s):  
Hana Sarashina-Kida ◽  
Hideo Negishi ◽  
Junko Nishio ◽  
Wataru Suda ◽  
Yuki Nakajima ◽  
...  

The commensal microbiota within the gastrointestinal tract is essential in maintaining homeostasis. Indeed, dysregulation in the repertoire of microbiota can result in the development of intestinal immune–inflammatory diseases. Further, this immune regulation by gut microbiota is important systemically, impacting health and disease of organ systems beyond the local environment of the gut. What has not been explored is how distant organs might in turn shape the microbiota via microbe-targeted molecules. Here, we provide evidence that surfactant protein D (SP-D) synthesized in the gallbladder and delivered into intestinal lumen binds selectively to species of gut commensal bacteria. SP-D–deficient mice manifest intestinal dysbiosis and show a susceptibility to dextran sulfate sodium-induced colitis. Further, fecal transfer from SP-D–deficient mice to wild-type, germ-free mice conveyed colitis susceptibility. Interestingly, colitis caused a notable increase inSftpdgene expression in the gallbladder, but not in the lung, via the activity of glucocorticoids produced in the liver. These findings describe a unique mechanism of interorgan regulation of intestinal immune homeostasis by SP-D with potential clinical implications such as cholecystectomy.


2021 ◽  
Vol 58 (1) ◽  
pp. 68-73
Author(s):  
O. C. Iacob

SummaryThe present study was carried out on 10 frogs, Pelophylax ridibundus (Pallas, 1771), captured near the river Bahlui, Iasi, between April and May, 2019, for the study of digestive helminths and their effect on the digestive tract. Macroscopic examination of the general cavity revealed distension of the small intestine. The sectioning of the intestinal wall revealed a variable number of parasites (1 – 12) with a whitish cylindrical body, anchored in the duodenal mucosa. The morphological study of the parasites confirmed the species as Acantocephalus ranae. The prevalence of the infection was 60 % and the average intensity was 4.83 ± 4.15. Lesions of the small intestine were characterized by catarrhal enteritis, hemorrhagic spots and ulcers on the mucosa, occlusion and obstruction of the intestinal lumen. Histologically, eosinophilic inflammatory infiltrate in the glandular crypts, mucosal and submucosal edema, fibrosis and conjunctival hyperplasia, total mucosal atrophy, were found. The infection with Acanthocephalus ranae in Pelophylax ridibundus caused severe pathological changes, conditioned by the intensity of the infection, aspects revealed for the first time in Romania.


2020 ◽  
Vol 13 (4) ◽  
pp. 344-347
Author(s):  
Islam Khuseynovich Shidakov

Intestinal intussusception is rare in children over the age of 6 years and, in most cases, is due to the presence of anatomical reasons. Tumors of the gastrointestinal tract are one of the etiological factors in the development of ileus in older children. The paper presents the case of a 7-year-old child who was admitted to the clinic with the abdominal pain syndrome that resolved on its own. With a repeated pain attack, intestinal intussusception was diagnosed, the patient was urgently operated. Laparoscopic complete reduction of intussusception failed, which required conversion of the access. After straightening the intussusception of the small intestine, there was detected a tumor of the ileum, which practically blocked the intestinal lumen. The segment of the intestine with the tumor was resected with an end-to-end anastomosis. In the postoperative period, the patient was diagnosed with intestinal lymphoma based on the test studies of the operating material. After stabilizing the condition, the child was transferred to an oncological center.


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