Magnesium Absorption Research Articles

Short bowel syndrome cause of hypomagnesaemia importance of its diagnosis and treatment

The short bowel syndrome (SIC) is a complex entity characterized by a malabsorptive state usually secondary to extensive intestinal resection originating a clinical, metabolic and/or nutritional disorder due to the reduction of the effective intestinal absorptive surface. The diagnosis is essentially clinical and, due to the patients malabsorptive process, it requires nutritional support to maintain their basic requirements, as the case reported. The clinical features of SIC patients depend on the grade of the alteration of function of the the small intestine or the impairment secondary to the surgical resection. We know that electrolytes are absorbed predominantly in the proximal gut. The regulation of ion/mineral levels depend on both the intestinal absorption and the renal excretion. We present an unusual case of SIC with only low absorption of magnesium. We discuss the most outstanding aspects of the case and review the literature.

Intracellular absorption of transdermal magnesium demonstrated by ESEM-EDS

Magnesium, the second most abundant intracellular cation in human body, plays a fundamental role in intracellular metabolism. As a cofactor in a huge number of key enzimatic reactions, magnesium is especially important for those enzymes that use nucleotides as cofactors or substrates (phosphotransferases, phosphohydrolases, etc.). The majority of magnesium studies were performed by detecting serum magnesium concentration, measure that doesn’t consider the intracellular uptake. In the present study, a different approach has been carried out. By means of an Environmental Scanning Electron Microscope (ESEM) equipped with an Energy Dispersive Spectroscopy (EDS) detector, the intracellular magnesium presence and uptake has been measured in a semiquantitative approach on samples of exfoliating epithelial cells from the oral mucosa [1]. The intracellular magnesium uptake has been experimentally induced by applying, twice a day and for 4 months, on the skin of healthy volunteers, a spray of a magnesium chlorate supersaturated solution. Epithelial cells and blood samples were collected at time zero and every 2 months of treatment. Despite the constant serum concentration of magnesium along the treatment and in absence of any side effect, the EDS analysis reveals a progressive and regular intracellular magnesium increasing of about 100% of the values at each experimental step. Results can confirm the high specificity and, more in general, the high reliability of the EDS analysis about a parameter that can result neglect utilizing only the serum concentration. Moreover, transdermal absorption of magnesium can represent an efficient way of magnesium administration, low dose and side effect free, to be utilize in chronic clinical magnesium deficiency [2].

Efficacy of oral potassium chloride administration in treating lactating dairy cows with experimentally induced hypokalemia, hypochloremia, and alkalemia

Hypokalemia occurs commonly in lactating dairy cows. The objectives of this study were to determine (1) whether a 24-h oral KCl dose of 0.4g/kg of body weight (BW) was effective and safe in hypokalemic cattle; (2) whether potassium was best administered as 2 large doses or multiple smaller doses over a 24-h period; and (3) the effect of oral KCl administration on plasma Mg concentration and urine Mg excretion in fasted lactating dairy cattle. Plasma K and Cl concentrations were decreased, and blood pH increased, in 15 lactating Holstein-Friesian cows by administering 2 intramuscular (i.m.) 10-mg injections of isoflupredone acetate 24h apart followed by 2 i.m. injections of furosemide (1mg/kg of BW) 8h apart and by decreasing feed intake. Cows were randomly assigned to 1 of 3 treatment groups with 5 cows/group: untreated control (group C); oral administration of KCl at 0.05g/kg of BW 8 times at 3-h intervals (group K3); and oral administration of KCl at 0.2g/kg of BW twice at 12-h intervals (group K12). A 24-h KCl dose rate of 0.4g/kg of BW increased plasma and milk K concentration and plasma Cl concentration, and corrected the metabolic alkalosis and alkalemia, with no clinically significant difference between 2 large doses (group K12) or multiple small doses (group K3) of KCl over 24 h. Oral KCl administration decreased peripheral fat mobilization in cattle with experimentally induced hypokalemia, as measured by changes in plasma nonesterified fatty acid concentration, and slightly augmented the fasting-induced decrease in plasma Mg concentration. Our findings support recommendations for a 24-h oral KCl dose of 0.4g/kg of BW for treating moderately hypokalemic cattle. Additional Mg may need to be administered to inappetant lactating dairy cattle being treated with oral KCl to minimize K-induced decreases in magnesium absorption.

Health-promoting effects in the gut and influence on lipid metabolism of Himanthalia elongata and Gigartina pistillata in hypercholesterolaemic Wistar rats

The intake of Himanthalia elongata and Gigartina pistillata from the Spanish Atlantic coasts was evaluated in Wistar rats. Both seaweed diets showed higher (p < 0.001) faecal excretion. Colonic fermentation increased (p < 0.001) total short-chain fatty acids (SCFAs) in Himanthalia-fed rats due to the higher (p < 0.001) levels of acetic, propionic and butyric acids. The intake of Gigartina increased (p < 0.001) propionic acid and decreased (p < 0.001) butyric acid. The apparent absorption and true retention of calcium and magnesium enhanced (p < 0.05) with Himanthalia diet, while Gigartina produced no significant effect. The serum concentration of HDL-C increased (p < 0.01), triglycerides (TGL) decreased (p < 0.001) and bile acids diminished (p < 0.001) in faeces of Himanthalia-fed rats. The Gigartina diet produced a decrease (p < 0.001) in TGL, total cholesterol (p < 0.01) and LDL-C (p < 0.05) in serum and reduced TGL in liver (p < 0.001). Thus, both seaweeds improved the lipid profile, and Himanthalia increased SCFA production and the absorption and retention of Ca and Mg as a result of the gut fermentation.

Reducing effect of calcium in combination with magnesium and lactulose on body fat mass in middle-aged Japanese women.

It has been reported that adequate calcium intake decreases body fat and appropriate intakes of magnesium suppress the development of the metabolic syndrome. Furthermore, lactulose increases the absorption of calcium and magnesium. An optimal combination of calcium, magnesium and lactulose may therefore reduce body fat mass. An open-label randomized controlled trial was conducted to investigate the body fat-reducing effects of a test food containing 300 mg calcium, 150 mg magnesium, and 4.0 g lactulose. Body composition parameters and blood hormone and urine mineral concentrations were measured at baseline and at 6 and 12 months thereafter. Whole-body fat mass was measured with dual-energy x-ray absorptiometry. Seventy-six middle-aged Japanese women (47.5±4.7 years) were randomized to the intake group (n=48) or the non-intake control group (n=28). At 12 months the difference in body fat mass change between the two groups (intake group - control group) was -0.8 kg (95% CI: -1.5 - 0.0 kg, p=0.046), although there were no differences in anthropometric data between the two groups. Body fat percentage at 12 months tended to be lower in the intake group, but the difference was not significant (p=0.09). These findings may suggest that calcium in combination with magnesium and lactulose can reduce body fat mass in middle-aged Japanese women. However, the contribution of magnesium and lactulose are unclear in this study. Further studies are needed to clarify these contributions.

Magnesium

Pantano, Francesco; Vincenzi, Bruno; Santini, Daniele; Tonini, Giuseppe Author Information

Hypomagnesaemia: A Harbinger of a Crohnʼs Flare

Purpose: Crohn's disease affects patients and with a spectrum of symptoms they individually classify as their “flare”. Classically, a Crohn's disease flare presents with abdominal, bloody diarrhea, mild tenesmus and symptoms of malabsorption such as steatorrhoea or vitamin deficiencies. We present a case of a male patient who presented with profound refractory hypomagnesemia as a sign of his Crohn's flare. A 71-year-old male presented with weakness, dizziness, lightheadedness, and an unsteady gait of 1 week duration. He also admitted to difficulties in concentrating and remembering things recently. The patient stated it had become so difficult to walk that he fell and sustained injuries 3 days prior to presentation. The patient denies any fever, chills, chest pain, or palpitations but did admit to non-bloody diarrhea and generalized abdominal pain that began on the day of admission. The patient stated he had never felt these symptoms before and were unlike his previous presentations. His history was significant for Crohn's disease, hypertension, hyperlipidemia and CABG 10 years prior. On physical exam his abdomen was soft and notable for only mild epigastric tenderness. A working diagnosis of ischemia or neurologic insult was entertained but the EKG was significant for sinus tachycardia without ST changes and troponins were negative. A CT of the head demonstrated no intracranial mass or hemorrhage. However a CT scan of the abdomen reveal thickening of the distal and terminal ileum suggestive of Crohn's disease. Additionally his labs demonstrated profound hypomagnesaemia of 0.4 mg/dL and hypocalcemia of 6.0 mg/dL with a normal albumin requiring a monitored setting. The patient also had a normal WBC count without left shift. The patient was not on any medications that would cause low magnesium, denied alcohol use, and had no evidence of renal disease. These low values persisted despite aggressive repletion through both IV and oral means. However through supportive care his flare subsided and the values of both electrolytes improved dramatically. The patient is currently doing well and has had no further bouts of Crohn's disease. His final magnesium level was 2.0 mg/dL on discharge. Hypomagnesaemia may be an early sign of Crohn's disease, as presented in this case; symptoms may precede the onset of a flare. The majority of magnesium absorption is in the small bowel; specifically in the distal ileum. Inflammation in this region prevents the transcellular transporter receptor channel melastatin TRPM 6 and 7 from absorbing magnesium. We recommend a prospective analysis of magnesium levels in patients with Crohn's flare to further correlate these findings.

An infant with recurrent convulsive seizures of 3 weeks duration: Questions

A 1-month-old Japanese boy was admitted to the hospital with a history of recurrent convulsive seizures of 3 weeks in duration. He was born at term (40 week gestation) at a normal birth weight of 2.76 kg following an uneventful pregnancy. He was the first child of healthy parents; there was no history of consanguinity. The infant was well until the 14th day of life when he developed convulsive seizures. On admission, the physicians observed tetanic manifestations, such as carpopedal spasms and convulsive seizures. The patient’s serum calcium level was 5.0 mg/dL (normal range 8.0–10.5 mg/dL), and the inorganic phosphate level was 6.2 mg/dL (normal range 2.5– 4.5 mg/dL). Calcium gluconate and parathyroid hormone (PTH) were administered intramuscularly in high doses, but the tetanic convulsions did not resolve. At that time, the serum magnesium level was measured and found to be extremely low at 0.16 mEq/L (normal range 1.44–1.81 mEq/L). The urinary excretion of magnesium was also low at 0.13 mEq/day (normal 0.31 mEq/L). Parenteral magnesium therapy (8 mEq/day) was started. After a few days, the serum concentrations of magnesium and calcium increased to nearly normal levels, and the tetanic manifestations disappeared completely. Oral magnesium therapy (magnesium chloride, 1 mEq/kg/day) has been continued without any further tetanic manifestations. The magnesium supplement was discontinued on two occasions, and the tetanic convulsions reappeared promptly. The fractional excretion of Mg for this patient was 2.7 % despite a very low level of serum magnesium (normal range 2.1–14.3 % in normagnesemic individuals, but is close to 0 if there is permanent depletion of magnesium), indicating the presence of a renal magnesium leak. The intestinal absorption of magnesium [(1−Mg in stool/Mg intake)×100 (%)] was lower than the amount of absorption observed in people with normal levels of magnesium (absorption in patient 19.6– 32.9 %; normal levels 50.2–60.2 %). The serum calcium and magnesium levels of the parents were within normal limits.

Hydrogen absorption of catalyzed magnesium below room temperature

Hydrogen absorption of magnesium (Mg) catalyzed by 1 mol% niobium oxide (Nb2O5) was demonstrated under the low temperature condition even at −50 °C. The kinetic and thermodynamic properties were examined for MgH2 with and without Nb2O5. By considering the remarkable absorption features at such low temperature, the essential hydrogen absorption properties were investigated under accurate isothermal conditions. As the results, the activation energy of hydrogen absorption for the catalyzed Mg was evaluated to be 38 kJ/mol, which was significantly smaller than that of MgH2 without the catalyst. The kinetic improvement was also found on the hydrogen desorption process. On the other hand, thermodynamic properties were not changed by the catalyst as a matter of course. Therefore, the Nb2O5 addition mainly affects the reaction rates between Mg and hydrogen and shows the excellent catalytic effects.

Perils and pitfalls of long-term effects of proton pump inhibitors

This review summarizes the literature regarding long-term adverse effects of proton pump inhibitors (PPIs). A PubMed search (1966 to February 2013) for English language studies was conducted using key terms PPI: omeprazole, esomeprazole, pantoprazole, lansoprazole, dexlansoprazole, rabeprazole, pneumonia, Clostridium difficile, osteoporosis, risk of fractures, thrombocytopenia, rhabdomyolysis, anemia, iron deficiency, hypomagnesemia, vitamin B12 and nephritis. The risk of pneumonia was increased 27–39% in short-term use of PPIs in three meta-analyses. C. difficile infections were also associated with the use of PPIs (odds ratio: 2.15; 95% CI: 1.81–2.55; p < 0.00001). This effect appears to be dose related. The US FDA has recently issued a warning regarding fractures and the impaired magnesium absorption associated with the use of PPI. Thrombocytopenia, iron deficiency, vitamin B12 deficiency, rhabdomyolysis and acute interstitial nephritis have also been reported with the use of PPIs. There is mounting evidence that PPIs are associated with serious adverse effects. Practitioners should be vigilant and counsel patients accordingly.

Magnesium intake and risk of amyotrophic lateral sclerosis: Results from five large cohort studies

A low magnesium intake has been suggested to be associated with amyotrophic lateral sclerosis (ALS) in pathological and case-control studies, but prospective studies in humans are lacking.The relation between dietary intake of magnesium and ALS risk was explored in five large prospective cohort studies (the Nurses’ Health Study, the Health Professionals Follow-up Study, the Cancer Prevention Study II Nutrition Cohort, the Multiethnic Cohort Study, and the National Institutes of Health – AARP Diet and Health Study), comprising over 1,050,000 males and females contributing 1093 cases of ALS during a mean of 15 years of follow-up. Cox proportional hazards models were used within each cohort, and cohort-specific estimates were subsequently pooled using a random-effects model. Results demonstrated that dietary magnesium intake was not associated with ALS risk, relative risk 1.07, 95% confidence interval 0.88 − 1.31 comparing the highest quintile of intake with the lowest. This finding does not support a protective effect of magnesium intake on ALS risk. Further analyses should explore magnesium intake in combination with heavy metal exposure and genetic variants affecting magnesium absorption.

Absorption Studies Show that Phytase from Aspergillus niger Significantly Increases Iron and Zinc Bioavailability from Phytate-Rich Foods

Iron and zinc deficiency are major public health problems affecting many parts of the world, including Southeast Asia. Infants, young children, and women of reproductive age are particularly vulnerable due to their high requirements. Even though iron and zinc are present in significant amounts in the plant-based diets typically consumed in developing countries, their bioavailability is low due to high levels of absorption inhibitors such as phytate. Phytase has been used in animal nutrition for decades to improve the bioavailability of certain minerals in feed. To show the effect of phytase in human nutrition based on evidence from human studies. Phytase can be used either during processing or as an active food ingredient degrading dietary phytate during stomach transit time. Evidence from human studies testing the effect of phytase on iron and zinc bioavailability using stable isotopes was reviewed. Twelve studies tested the effect of phytase on iron and five tested its effect on zinc bioavailability. Most of these studies used a phytase derived from Aspergillus niger. They found a beneficial effect unless phytate concentrations were too low or levels of inhibitors or enhancers of iron absorption were too high. Twenty to 320 phytase units per 100 g of flour significantly improved iron absorption, even though higher levels might further increase iron bioavailability. For zinc, not enough information is available to determine optimal activities. Phytase clearly has a beneficial effect on iron and zinc absorption from phytate-rich foods. It also has the potential to increase the absorption of magnesium, calcium, and phosphorus in areas such as Southeast Asia where mineral deficiencies are widespread.

Clinical Implications

HomeHypertensionVol. 61, No. 6Clinical Implications Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBClinical Implications Originally published1 Jun 2013https://doi.org/10.1161/HYP.0b013e318297fcdeHypertension. 2013;61:1141Magnesium and Risk of Hypertension (page 1161)Although dietary macro minerals, not only sodium and potassium but also calcium, are thought to play an important role in the primary prevention and control of high blood pressure, less attention has been paid to the possible effects of magnesium. Previous studies used circulating magnesium, which is regulated within a narrow, homeostatic range and may be compensated by magnesium from muscle and bone making it less reflective of dietary intake. Other studies relied on subjective measures of magnesium intake assessed by dietary recall, which correlates moderately with actual systemic magnesium absorption. In this issue of Hypertension, Joosten et al used urinary excretion of magnesium, as estimate of dietary uptake, to assess the association between magnesium and risk of hypertension. Two 24-hour urine collections were obtained from 5511 participants of the prospective, population-based Prevention of Renal and Vascular End-Stage Disease Study. Participants were free of hypertension at baseline and were followed for a median of 7.6 years. Urinary magnesium excretion was strongly and inversely associated with risk of hypertension. This association seemed to be independent of other dietary and nondietary risk factors of hypertension. As expected, no associations were observed between plasma magnesium and risk of hypertension. The current findings could have substantial public health implications given the highly prevalent inadequate magnesium intake in Western societies combined with the enormous burden associated with hypertension.Download figureDownload PowerPointHigh Blood Pressure and White Matter Lesion Progression (page 1354)Download figureDownload PowerPointCerebral white matter lesions (WMLs) are highly frequent in the aging population and increase the risk of stroke and dementia. Slowing down the progression of WMLs can, therefore, potentially lead to a lower incidence of stroke and dementia. The exact pathogenesis of WMLs is still unknown, but converging evidence suggests that high blood pressure is one of the most important determinants for WMLs. Nevertheless, the longitudinal and temporal association between blood pressure and WMLs is not yet entirely elucidated. In this issue of Hypertension, Verhaaren et al report on a population-based MRI-study that investigated how blood pressure levels in the preceding 5 years were related to WML progression during the subsequent 3.5 years. They found that both high systolic and high diastolic blood pressure preceded WML progression and that antihypertensive treatment was associated with less WML progression. The results of Verhaaren et al further add to the evidence suggesting that high blood pressure is causally related to WML progression and indicate that antihypertensive treatment may be beneficial in reducing WML progression in the general population.Blood Pressure Lowering and Cerebral Blood Flow in the Elderly (page 1309)Hypertension frequently leads to adverse effects on the brain. Stroke was recognized as a complication long ago, but the association with cognitive decline and dementia is a more recent finding. Hypertension leads to increased rates of age-associated brain atrophy and small vessel disease which are likely to account for this association. The optimal treatment target for hypertension is unclear, particularly in older people, where many physicians are concerned about causing adverse events caused by brain hypoperfusion. It has been suggested that lowering blood pressure (BP) might accelerate small vessel disease progression. A better understanding of the effects of BP lowering on cerebral blood flow regulation in older people is required.In this issue of Hypertension, Tryambake et al report a randomized controlled trial comparing the effect of 12-week intensive (target BP, <130/80 mm Hg) and usual (target BP, <140/90 mm Hg) BP lowering on cerebral blood flow using serial noninvasive MR arterial spin labeling. Cerebral blood flow increased by 10% with intensive BP lowering but was unchanged with usual BP lowering. These findings are contrary to what many physicians might predict but consistent with previous nonrandomized studies. These findings suggest that BP lowering more intensive than current guideline recommendations might benefit older people’s brains and support the undertaking of long-term intervention trials to determine whether more intensive BP reduces the risk of cognitive decline and dementia.Download figureDownload PowerPoint Previous Back to top Next FiguresReferencesRelatedDetails June 2013Vol 61, Issue 6 Advertisement Article InformationMetrics © 2013 American Heart Association, Inc.https://doi.org/10.1161/HYP.0b013e318297fcde Originally publishedJune 1, 2013 PDF download Advertisement

Urinary Magnesium Excretion and Risk of Hypertension

Observational studies on dietary or circulating magnesium and risk of hypertension have reported weak-to-modest inverse associations, but have lacked measures of actual dietary uptake. Urinary magnesium excretion, an indicator of intestinal magnesium absorption, may provide a better insight in this association. We examined 5511 participants aged 28 to 75 years free of hypertension in the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study, a prospective population–based cohort study. Circulating magnesium was measured in plasma and urinary magnesium in two 24-hour urine collections, both at baseline. Incident hypertension was defined as blood pressure ≥140 mm Hg systolic or ≥90 mm Hg diastolic, or initiation of antihypertensive medication. During a median follow-up of 7.6 years (interquartile range, 5.0–9.3 years), 1172 participants developed hypertension. The median urinary magnesium excretion was 3.8 mmol/24 hour (interquartile range, 2.9–4.8 mmol/24 hour). Urinary magnesium excretion was associated with risk of hypertension in an inverse log-linear fashion, and this association remained after adjustment for age, sex, body mass index, smoking status, alcohol intake, parental history of hypertension, and urinary excretion of sodium, potassium, and calcium. Each 1-unit increment in ln-transformed urinary magnesium excretion was associated with a 21% lower risk of hypertension after multivariable adjustment (adjusted hazard ratio, 0.79; 95% confidence interval, 0.71–0.88). No associations were observed between circulating magnesium and risk of hypertension. In conclusion, in this cohort of men and women, urinary magnesium excretion was inversely associated with risk of hypertension across the entire range of habitual dietary intake.

A mixture of GOS/FOS [reg] added to a low calcium (ca) diet improved ca, phosphorus (p) and magnesium (mg) absorption: experimental model in normal growing rats

Searchable abstracts of presentations at key conferences on calcified tissues ISSN 2052-1219 (online)

マグネシウムの水素吸蔵/放出における五酸化ニオビウムの触媒効果

Hydrogen absorption of magnesium (Mg) catalyzed by 1 mol% niobium oxide (Nb2O5) was demonstrated under the low temperature condition even at −50℃. The kinetic and thermodynamic properties were examined for MgH2 with and without Nb2O5. By considering the remarkable absorption features at such low-temperature, the essential hydrogen absorption properties were investigated under accurate isothermal conditions. As a result, the activation energy of hydrogen absorption for the catalyzed Mg was evaluated to be 38 kJ•mol−1, which was significantly smaller than that of MgH2 without the catalyst. The kinetic improvement was also found on the hydrogen desorption process. On the other hand, thermodynamic properties were not changed by the catalyst. Therefore, the Nb2O5 addition mainly affects the reaction rates between Mg and hydrogen and shows the excellent catalytic effects.

Mannitol improves absorption and retention of calcium and magnesium in growing rats

ObjectiveResistant sugars, which have several desirable properties, are often used in food production and the pharmaceutical industry. We evaluated the effects of mannitol on the absorption and retention of calcium (Ca) and magnesium (Mg) in growing rats. MethodsIn experiment 1, 4-wk-old growing male Wistar rats were given a control diet (C) or mannitol diets containing 2%, 4%, 6%, or 8% mannitol (2M, 4M, 6M, or 8M, respectively) for 28 d to measure the absorption and retention of Ca and Mg. In the last 7 d of the feeding trial, the non-absorbable marker chromium-mordant cellulose was added to the experimental diets to estimate Ca and Mg absorbability in the intestinal segments. In experiment 2, 9-wk-old growing male Wistar rats were fed for 7 d with the experimental diets (C, 4M, or 8M) to observe cecal parameters. ResultsApparent Ca absorption and retention in bone were significantly increased by 6M and 8M. Apparent Mg absorption was significantly increased by 4M, 6M, and 8M, whereas Mg retention in bone was significantly increased by 8M. The Ca/Cr and Mg/Cr in cecal digesta were similar in all groups. Fecal Ca/Cr was significantly decreased by 6M and 8M and Mg/Cr was significantly decreased by 4M, 6M, and 8M. In experiment 2, cecal weight and tissue weight were significantly increased by 8M. A significant decrease in pH was concomitant with a significant change in cecal organic acid concentrations after mannitol consumption. ConclusionAbsorption and retention of Ca and Mg are promoted by mannitol feeding through the fermentation of mannitol in the cecum.

Modeling and Simulation of the Effect of Proton Pump Inhibitors on Magnesium Homeostasis. 1. Oral Absorption of Magnesium

Prolonged use of proton pump inhibitors has reportedly caused rare clinically symptomatic hypomagnesemia. A review of the literature suggests PPI drugs may impair intestinal magnesium absorption. With the goal of preventing PPI-induced hypomagnesemia, an oral absorption-centric model was developed by referencing literature data. Our modeling with human data reveals that magnesium absorption is substantial in the distal intestine. We then perform simulations by referring to the reported reduction in mid to distal intestinal pH caused by one week of oral esomeprazole, and to reported reduction of the divalent cation-sensitive current when the carboxyl side chains of glutamic and aspartic residues in the binding channels of TRPM6/TRPM7 were neutralized. Our simulations reveal that short-term PPI therapy may cause a very small reduction (5%) in the serum magnesium level, which is qualitatively consistent with the reported 1% reduction in magnesium absorption following 1 week of omeprazole in humans. Simulations provide insight into the benefit of frequent but small dose of magnesium supplementation in maintaining the serum magnesium level when magnesium deficiency occurs.

Désordres de la magnésémie

Extracellular content in magnesium represents about 1% of total body content, of which plasma magnesium is thus a poor reflect. Hypomagnesaemia is defined by a value lesser than 0.65mmol/L. Its incidence in hospitalized patients ranges between 10 and 15%. Identification of the physiopathology of hypomagnesaemia relies first upon concomitant measurement of plasma and urinary magnesium concentration. Daily magnesium excretion lesser than 1mmol/L or EFMg lesser than 1% sign extra renal origin, due to either low magnesium intake, low intestinal absorption of magnesium or derivation of extracellular magnesium toward bone, such as in bone reparation process after hyperparathyroidism surgery. Daily magnesium excretion higher than 2mmol/L concomitant to hypomagnesaemia indicates native or acquired renal loss of magnesium. Congenital renal and extra-renal losses of magnesium are mainly related to rare monogenic disease, and are inconstantly associated with a renal loss of sodium, potassium and calcium. Recent progress in the genetics of this rare diseases have greatly improved the knowledge about proteins involved in intestinal abortion, renal renal tubular re-absorption of magnesium and its regulations. Hypermagnesemia is a rarer metabolic disorder than hypomagnesemia (about 5% of hospitalized patients). Asymptomatic below 2mmol/L, it progressively alters neuromuscular transmission, autonomic sympathic activity and cardiac conduction, with vital risk above 7mol/L. It is due to acute magnesium input into extracellular volume most often associated with a decrease in glomerular filtration rate, limiting the high physiological ability to excrete magnesium input.

Cultivo de gladíolos em função das doses de calcário e potássio

Para o cultivo do gladíolo no Cerrado, caracterizado por solos de baixa fertilidade e elevada acidez, faz-se necessário o uso de corretivo agrícola e fertilização, especialmente a potássica. Assim, o objetivo desta pesquisa foi avaliar o efeito de diferentes doses de calcário e de potássio na produção comercial de plantas de gladíolo, cultivadas em um Latossolo Vermelho Distroférrico. O experimento foi conduzido na UFGD, em Dourados (MS). O delineamento experimental constou de blocos casualizados com quatro repetições, sendo que a unidade experimental foi composta por duas plantas de gladíolos, cultivar Peter Pears, cultivadas em vaso plástico de 5 L. Os tratamentos foram arranjados em parcelas subdivididas, sendo que nas parcelas foram alocadas as cinco doses de calcário dolomítico (0, 1, 2, 4 e 8 t ha-1) e, nas sub-parcelas, as cinco doses de K2O (0, 20, 40, 80 e 160 kg ha-1), utilizando-se como fonte o cloreto de potássio (KCl). Determinaram-se o comprimento das folhas, o início da floração, a durabilidade e o número de botões florais, a altura da planta e o comprimento das espigas. Após a floração, avaliou-se a matéria fresca, comprimento e diâmetro dos cormos produzidos e o teor de nutrientes da parte aérea. O comprimento das folhas, início da floração e durabilidade dos botões florais não foram influenciados pela calagem nem pela adubação potássica. O excesso de K e CaCO3 foram prejudiciais à altura da planta e ao comprimento da espiga floral, reduzindo o número de botões florais e o diâmetro dos cormos produzidos; doses elevadas de K2O diminuíram a absorção de magnésio pelas plantas. Conclui-se que as doses de calcário e potássio estudadas não foram eficientes para produzir plantas de gladíolo classificadas comercialmente como extras.