Is there a relationship between hypomagnesemia and proton-pump inhibitors in patients on chronic hemodialysis?

Effects of Proton Pump Inhibitors on Patient Survival in Patients Undergoing Maintenance Hemodialysis

Data to draw definite conclusions regarding the association between proton pump inhibitor (PPI) and all-cause mortality in patients undergoing hemodialysis (HD) remain insufficient. The object of this retrospective study was to assess the impact of PPIs on patient survival within a substantial cohort of individuals receiving maintenance HD. To achieve this, the study employed laboratory and clinical data sourced from the 4th, 5th, and 6th National HD Quality Assessment Programs. The programs included patients undergoing maintenance HD (n = 54,903). Based on the PPI prescription data collected over the 6-month HD quality assessment, the patients were categorized into three groups: Group 1, comprising individuals with not prescription; Group 2, consisting of patients prescribed PPIs for less than 90 days; and Group 3, comprising patients prescribed PPIs for 90 days or more. The respective number of patients in Groups 1, 2, and 3 was 43,059 (78.4%), 5065 (9.2%), and 6779 (12.3%), respectively. Among the study groups, the 5-year survival rates were as follows: Group 1-70.0%, Group 2-68.4%, and Group 3-63.0%. The hazard ratio for Group 3 was 1.09 (95% CI, 1.04 to 1.15; p < 0.001) and 1.10 (95% CI, 1.03 to 1.18; p = 0.007) compared to Groups 1 or 2 based on multivariable analysis. Multivariable analyses revealed a lower rate of patient survival in Group 3 compared to the other groups, while Groups 1 and 2 exhibited similar patient survival rates. Our study revealed a significant association between long-term PPI usage and increased mortality among patients undergoing HD. However, distinct trends were observed in subgroup analyses. The association between long-term PPI usage and mortality was prominent in patients who did not have a high gastrointestinal burden or comorbidities. Meanwhile, this association was not observed in patients who did have a high gastrointestinal burden or comorbidities.

Lansoprazole Increases Inorganic Pyrophosphate in Patients with Pseudoxanthoma Elasticum: A Double-Blind, Randomized, Placebo-Controlled Crossover Trial

Pseudoxanthoma elasticum (PXE) is characterized by low levels of inorganic pyrophosphate (PPi) and a high activity of tissue-nonspecific alkaline phosphatase (TNAP). Lansoprazole is a partial inhibitor of TNAP. The aim was to investigate whether lansoprazole increases plasma PPi levels in subjects with PXE. We conducted a 2 × 2 randomized, double-blind, placebo-controlled crossover trial in patients with PXE. Patients were allocated 30 mg/day of lansoprazole or a placebo in two sequences of 8 weeks. The primary outcome was the differences in plasma PPi levels between the placebo and lansoprazole phases. 29 patients were included in the study. There were eight drop-outs due to the pandemic lockdown after the first visit and one due to gastric intolerance, so twenty patients completed the trial. A generalized linear mixed model was used to evaluate the effect of lansoprazole. Overall, lansoprazole increased plasma PPi levels from 0.34 ± 0.10 µM to 0.41 ± 0.16 µM (p = 0.0302), with no statistically significant changes in TNAP activity. There were no important adverse events. 30 mg/day of lansoprazole was able to significantly increase plasma PPi in patients with PXE; despite this, the study should be replicated with a large number of participants in a multicenter trial, with a clinical end point as the primary outcome.

Acquired Disorders of Hypomagnesemia

Magnesium disorders are common in clinical practice and when present can manifest clinically as cardiovascular, neuromuscular, or other organ dysfunction. Hypomagnesemia is far more common than hypermagnesemia, which is largely seen in patients with reduced glomerular filtration rates receiving magnesium-containing medications. In addition to inherited disorders of magnesium handling, hypomagnesemia is also seen with excessive gastrointestinal or renal losses and due to medications such as amphotericin B, aminoglycosides, and cisplatin. Laboratory assessment of body magnesium stores largely relies on the measurement of serum magnesium levels that are a poor proxy for total body stores but does correlate with the development of symptoms. Replacement of magnesium can be challenging, with oral replacement strategies being generally more effective at slowly replacing body stores but intravenous replacement being more effective at treating the more life-threatening and severe cases of hypomagnesemia. We conducted a thorough review of the literature using PubMed (1970-2022) and the search terms magnesium, hypomagnesemia, drugs, medications, treatment, and therapy. In the absence of clear data on optimal management of hypomagnesemia, we have made recommendations on magnesium replacement based on our clinical experience.

Choosing the right chronic medication for hemodialysis patients. A short ABC for the dialysis nephrologist

BACKGROUND

Adapting drug treatments for patients on hemodialysis with multiple chronic pathologies is a complex affair. When prescribing a medication, the risk-benefit analysis usually focuses primarily on the indication of the drug class prescribed. However, the pharmacokinetics of the chosen drug should also be taken into account. The purpose of our review was to identify the drugs to be favored in each therapeutic class, according to their safety and pharmacokinetic profiles, for the most common chronic diseases in patients on chronic hemodialysis.

METHODS

We conducted a narrative review of the literature using Medline and Web of Science databases, targeting studies on the most commonly-prescribed drugs for non-communicable diseases in patients on chronic hemodialysis.

RESULTS

The search identified 1224 articles, 95 of which were further analyzed. The main classes of drugs included concern the cardiovascular system (anti-hypertensives, anti-arrhythmics, anti-thrombotics, hypocholesterolemics), the endocrine and metabolic pathways (anti-diabetics, gastric anti-secretory, anticoagulant, thyroid hormones, anti-gout) and psychiatric and neurological disorders (antidepressants, anxiolytics, antipsychotics and anti-epileptics).

CONCLUSION

We report on the most often prescribed drugs for chronic pathologies in patients on chronic hemodialysis. Most of them require adaptation, and in some cases one better alternative stands out among the drug class. More pharmacokinetic data are needed to define the pharmacokinetics in the various dialysis techniques.

Hypomagnesemia as a Risk Factor and Accelerator for Vascular Aging in Diabetes Mellitus and Chronic Kidney Disease

The age-old axiom that one is as old as his or her vessels are, calls for ongoing critical re-examination of modifiable risk factors of accelerated vascular ageing in chronic kidney diseases. Attempts to modulate vascular risk with cholesterol-lowering agents have largely failed in advanced chronic kidney disease (CKD). In addition to nitrogen waste products, many pathological biochemical processes also play a role in vascular calcification in chronic kidney damage. Magnesium, a cation vital for the body, may substantially reduce cardiovascular diseases' risk and progression. This narrative review aimed to address the relationship between hypomagnesemia and vascular calcification, which promotes further cardiovascular complications in diabetes, aging, and CKD. Articles with predefined keywords were searched for in the PubMed and Google Scholar databases with specific inclusion and exclusion criteria. We hypothesized that a decrease in serum magnesium levels contributes to increased vascular calcification and thereby increases cardiovascular mortality. In summary, based on existing evidence in the literature, it appears that simple and inexpensive oral magnesium supplementation may reduce the cardiovascular mortality of patients who are already severely affected by such diseases; in this context, the concept of 'normal' vs. 'ideal' serum magnesium levels should be carefully re-examined.

Fibroblast growth factor 23 is independently associated with renal magnesium handling in patients with chronic kidney disease

BACKGROUND

Disturbances in magnesium homeostasis are common in patients with chronic kidney disease (CKD) and are associated with increased mortality. The kidney is a key organ in maintaining normal serum magnesium concentrations. To this end, fractional excretion of magnesium (FEMg) increases as renal function declines. Despite recent progress, the hormonal regulation of renal magnesium handling is incompletely understood. Fibroblast Growth Factor 23 (FGF23) is a phosphaturic hormone that has been linked to renal magnesium handling. However, it has not yet been reported whether FGF23 is associated with renal magnesium handling in CKD patients.

METHODS

The associations between plasma FGF23 levels, plasma and urine magnesium concentrations and FEMg was investigated in a cross-sectional cohort of 198 non-dialysis CKD patients undergoing renal biopsy.

RESULTS

FGF23 was significantly correlated with FEMg (Pearson's correlation coefficient = 0.37, p<0.001) and urinary magnesium (-0.14, p=0.04), but not with plasma magnesium. The association between FGF23 and FEMg remained significant after adjusting for potential confounders, including estimated glomerular filtration rate (eGFR), parathyroid hormone and 25-hydroxyvitamin D.

CONCLUSIONS

We report that plasma FGF23 is independently associated with measures of renal magnesium handling in a cohort of non-dialysis CKD patients. A potential causal relationship should be investigated in future studies.

Magnesium intake by enteral formulation affects serum magnesium concentration in patients undergoing hemodialysis

Decreased serum magnesium levels are associated with mortality and fractures in patients with chronic kidney disease; however, there is no recommendation for Mg intake in these populations. This study used cross-sectional analysis to examine the association between Mg intake and serum Mg levels in patients undergoing hemodialysis. Sixty-one patients were included. The daily Mg intake was 185 mg (IQR: 151-203 mg), and serum Mg level was 2.4 mg/dL (IQR: 2.2-2.7 mg/dL). Multiple regression analysis showed that intake of enteral formulation by tube feeding was an independent factor associated with serum Mg level (B = 0.90 [95% confidence interval: 0.61-1.20], p < 0.01). These findings may aid in serum Mg level management through diet and enteral formulation in patients undergoing hemodialysis.

An overview of diagnosis and management of drug-induced hypomagnesemia

Magnesium (Mg) is commonly addressed as the "forgotten ion" in medicine. Nonetheless, hypomagnesemia should be suspected in clinical practice in patients with relevant symptomatology and also be considered a predisposing factor for the development of other electrolyte disturbances. Furthermore, chronic hypomagnesemia has been associated with diabetes mellitus and cardiovascular disease. Hypomagnesemia as a consequence of drug therapy is relatively common, with the list of drugs inducing low serum Mg levels expanding. Culprit medications linked to hypomagnesemia include antibiotics (e.g. aminoglycosides, amphotericin B), diuretics, antineoplastic drugs (cisplatin and cetuximab), calcineurin inhibitors, and proton pump inhibitors. In recent years, the mechanisms of drug-induced hypomagnesemia have been unraveled through the discovery of key Mg transporters in the gut and kidney. This narrative review of available literature focuses on the pathogenetic mechanisms underlying drug-induced hypomagnesemia in order to increase the insight of clinicians toward early diagnosis and effective management.

Association between serum magnesium levels and abdominal aorta calcification in patients with pre-dialysis chronic kidney disease stage 5

BACKGROUND

Several studies have revealed the relationship between serum magnesium levels and vascular calcification in chronic kidney disease patients. Despite excellent predictability of abdominal aorta calcification for cardiovascular disease events, the relationship between serum magnesium levels and abdominal aorta calcification, as evaluated by quantitative methods, in pre-dialysis patients remains unclear. This study aimed to determine the abdominal aorta calcification volume using computerized tomography and its association with serum magnesium levels in pre-dialysis chronic kidney disease stage 5 patients.

METHODS

This single-center cross-sectional study included 100 consecutive patients with pre-dialysis chronic kidney disease stage 5 between January 2016 and May 2020 at Aichi Medical University Hospital, Japan. The relationships between serum magnesium levels and the abdominal aorta calcification volume were assessed using multiple linear regression models after adjusting for clinically relevant factors. We also assessed clinical factors that affect serum magnesium levels.

RESULTS

The mean serum magnesium level was 2.0 mg/dL (interquartile range, 1.8 to 2.3). Multivariate analyses revealed that a higher serum magnesium level (stand. β = -0.245, p = 0.010) was significantly associated with a reduced abdominal aorta calcification volume, and that a history of cardiovascular disease (stand. β = 0.3792, p < 0.001) and older age (stand. β = 0.278, p = 0.007) were significantly associated with an increased abdominal aorta calcification volume. Moreover, multivariate analysis showed that the use of proton pump inhibitor or potassium-competitive acid blocker was significantly associated with lower serum magnesium levels (stand. β = -0.246, p = 0.019).

CONCLUSIONS

The present study revealed that the higher Mg level was significantly associated with lower volume of abdominal aorta calcification in pre-dialysis chronic kidney disease stage 5 patients. Further studies should be undertaken to determine the appropriate magnesium level to suppress vascular calcification.

Use of proton pump inhibitors in dialysis patients: a double-edged sword?

Large cohort-based studies have shown that proton pump inhibitors (PPIs) are linked to rare but multiple and varied secondary events when used in the general population. Although clinicians accept the negative effects of PPIs on renal function, there is a lack of available data regarding the potential consequences of their use by dialysis patients in whom the risk of gastrointestinal bleeding is quite high. This review aims to highlight the risks and benefits of PPIs use in dialysis patients. To summarize, the benefit on the reduction of high digestive bleeding seems certain, but without any beneficial impact on overall survival. The impact on quality of life seems to be significant. The data on the occurrence of peritonitis during PPIs treatment are very contradictory. There is evidence regarding the occurrence of hypomagnesaemia in haemodialysis patients with PPIs; which may lead to increase bone fragility. New data show an increased cardiovascular risk and even a risk of death linked to the use of PPIs on dialysis. Several mechanisms of IPP toxicity are advanced to explain these findings.

Use of proton pump inhibitors is associated with an increase in adverse cardiovascular events in patients with hemodialysis: Insight from the kids registry

BACKGROUND

Proton pump inhibitors (PPIs) are known to increase the risk of mortality and cardiovascular events in the general population. However, in patients with maintenance hemodialysis, PPI effects are under investigated.

METHODS

We analyzed the risk of PPIs for cardiovascular events using the Kagoshima Dialysis (KIDS) registry, a prospective, multicenter, observational study in patients with maintenance hemodialysis in Japan.

RESULTS

In all, 531 patients were enrolled from June 2015 to December 2018. One-year follow-up data were available for 376 patients (Use of PPIs at baseline (PPI group): 217 patients and without PPIs (No PPI group): 159 patients). The incidence of a composite outcome (all-cause mortality, non-fatal myocardial infarction, or non-fatal stroke) was higher in patients in the PPI group than the No PPI group (15.2% vs. 4.4%; hazard ratio (HR): 3.65, 95% confidence interval (CI): 1.61-8.23, P = 0.002). In the multivariate analysis, even after adjustment for covariates, the use of PPIs was an independent risk factor for a composite outcome (HR: 2.38, 95% CI: 1.02-5.54, P = 0.045). We performed propensity score matching analysis as a sensitivity analysis, showing a consistent result. The incidence of bleeding showed no difference between the two groups (15.7% vs. 11.3%; HR: 1.46, 95% CI: 0.83-2.59, P = 0.19).

CONCLUSIONS

These results indicate that the use of PPIs in patients with maintenance hemodialysis might increase mortality and cardiovascular events without decreasing the risk of bleeding. Therefore, it should always be analyzed if a patient truly needs PPIs.

Proton pump inhibitors and hypomagnesemia: A meta-analysis of observational studies

BACKGROUND

Previous meta-analyses have suggested that there might be an association between the use of proton pump inhibitors (PPIs) and the development of hypomagnesemia, although the conclusions were no definitive.

METHODS

To provide an update on this topic, we performed a meta-analysis of all observational studies that examined the association between the use of PPIs and the development of hypomagnesemia. A literature search was conducted in MEDLINE, Scopus and Cochrane Central Register of Controlled Trials (January 1970 to June 2018) to identify observational studies that examined the association between the use of PPIs and the incidence and prevalence of hypomagnesemia.

STUDY ELIGIBILITY CRITERIA

In the absence of randomized controlled trials, we focused primarily on observational studies, including cross-sectional, case-control, retrospective, and prospective cohort studies. There was no limitation on sample size or study duration. Random-effect models meta-analyses were used to compute pooled unadjusted and adjusted odds ratios (ORs) for binary variables.

RESULTS

Sixteen observational studies were identified, including 13 cross-sectional studies, 2 case-control studies, and 1 cohort study, with a total of 131,507 patients. The pooled percentage of PPI users was 43.6% (95% confidence interval [CI] 25.0%, 64.0%). Among PPI users, 19.4% (95% CI 13.8%, 26.5%) had hypomagnesemia compared to 13.5% (95% CI 7.9%, 22.2%) among nonusers. By meta-analysis, PPI use was significantly associated with hypomagnesemia, with a pooled unadjusted OR of 1.83 (95% CI 1.26, 2.67; P = .002) and a pooled adjusted OR of 1.71 (95% CI 1.33, 2.19; P < .001). In subgroup analyses, high-dose PPI use was associated with higher odds for hypomagnesemia relative to low-dose PPI use (pooled adjusted OR 2.13; 95% CI 1.26, 3.59; P = .005).

CONCLUSION

Our findings are in support of the results of the previous meta-analyses. Furthermore, we found a dose-response between the PPI use and development of hypomagnesemia.

Proton Pump Inhibitors and the Kidney: Implications of Current Evidence for Clinical Practice and When and How to Deprescribe

Proton pump inhibitors (PPIs), long thought to be safe, are associated with a number of nonkidney adverse health outcomes and several untoward kidney outcomes, including hypomagnesemia, acute kidney injury, acute interstitial nephritis, incident chronic kidney disease, kidney disease progression, kidney failure, and increased risk for all-cause mortality and mortality due to chronic kidney disease. PPIs are abundantly prescribed, rarely deprescribed, and frequently purchased over the counter. They are frequently used without medical indication, and when medically indicated, they are often used for much longer than needed. In this In Practice review, we summarize evidence linking PPI use with adverse events in general and adverse kidney outcomes in particular. We review the literature on the association of PPI use and risk for hypomagnesemia, acute kidney injury, acute interstitial nephritis, incident chronic kidney disease, kidney disease progression, end-stage kidney disease, and death. We provide an assessment of how this evidence should inform clinical practice. We review the impact of this evidence on patients' perception of risk, synthesize PPI deprescription literature, and provide our recommendations on how to approach PPI use and deprescription.

Proton Pump Inhibitors and Fracture Risk: A Review of Current Evidence and Mechanisms Involved

The number of patients with gastroesophageal problems taking proton pump inhibitors (PPIs) is increasing. Several studies suggested a possible association between PPIs and fracture risk, especially hip fractures, but the relationship remains contentious. This review aimed to investigate the longitudinal studies published in the last five years on the relationship between PPIs and fracture risk. The mechanism underlying this relationship was also explored. Overall, PPIs were positively associated with elevated fracture risk in multiple studies (n = 14), although some studies reported no significant relationship (n = 4). Increased gastrin production and hypochlorhydria are the two main mechanisms that affect bone remodeling, mineral absorption, and muscle strength, contributing to increased fracture risk among PPI users. As a conclusion, there is a potential relationship between PPIs and fracture risks. Therefore, patients on long-term PPI treatment should pay attention to bone health status and consider prophylaxis to decrease fracture risk.

Does the use of proton pump inhibitors increase the risk of hypomagnesemia: An updated systematic review and meta-analysis

BACKGROUND

Proton pump inhibitors (PPIs) are commonly used in the treatment of acid-related diseases; however, the association between the use of PPIs and potential risk of hypomagnesemia is controversial.

METHODS

In the present study, databases including PubMed, EMBASE, MEDLINE, PsycINFO, CINAHL, the Cochrane Library, and 4 Chinese databases were searched since the inception until April 2018. Previous observational studies on the incidence of hypomagnesemia in individuals exposed to PPIs were included.

RESULTS

This systematic review involved 15 studies including 129,347 participants, and the sample size varied from 52 to 95,205. Meta-analysis of 14 studies indicated that the use of PPIs increased the risk of hypomagnesemia [RR, 1.44, 95% CI, 1.13-1.76; I, 85.2%]. Subgroup analysis revealed that the use of PPI was not associated with the incidence of hypomagnesemia in outpatients [RR, 1.49; 95% CI, 0.83-2.14; I, 41.4%] and hospitalized patients [RR, 1.05; 95% CI, 0.81-1.29; I, 62.1%], respectively. The use of PPIs was not related to the risk of hypomagnesemia based on the cut-off values of 1.8 mg/dL [RR, 1.73; 95% CI, 0.87-2.58; I, 65.2%], 1.7 mg/dL [RR, 1.48; 95% CI, 0.90-2.06; I, 87.6%], and 1.6 mg/dL [RR, 0.98; 95% CI, 0.69-1.27; I, 67.9%].

CONCLUSION

The association between the exposure to PPI and the incidence of hypomagnesemia remained unclear. Due to the remarkable heterogeneity in previous studies, a definitive conclusion could not be drawn. Further research should be conducted to investigate the relationship between the use of individual PPI and potential risk of hypomagnesemia, and a dose-response analysis may be required.

The risks of long-term use of proton pump inhibitors: a critical review

Proton pump inhibitors (PPIs) are among the most frequently prescribed medications. Their use is likely even higher than estimated due to an increase in the number of PPIs available without a prescription. Appropriate indications for PPI use include Helicobacter pylori infection, erosive esophagitis, gastric ulcers, and stress ulcer prevention in high-risk critically ill patients. Unfortunately, PPIs are often used off-label for extended periods of time. This increase in PPI usage over the past two decades has called into question the long-term effects of these medications. The association between PPI use and infection, particularly Clostridium difficile and pneumonia, has been the subject of several studies. It’s proposed that the alteration in gastrointestinal microflora by PPIs produces an environment conducive to development of these types of infections. At least one study has suggested that long-term PPI use increases the risk of dementia. Drug interactions are an important and often overlooked consideration when prescribing any medication. The potential interaction between PPIs and antiplatelet agents has been the subject of multiple studies. One of the more recent concerns with PPI use is their role in the development or progression of chronic kidney disease. There is also some literature suggesting that PPIs contribute to the development of various micronutrient deficiencies. Most of the literature examining the potential adverse effects of PPI use is composed of retrospective, observation studies. There is a need for higher quality studies exploring this relationship.

Y. Chiu D, Kalra PA, Green D. Prevalence and outcomes of proton pump inhibitor associated hypomagnesemia in chronic kidney disease

Background

Proton pump inhibitors (PPIs) are one of the most widely prescribed medications across the world. PPIs have been associated with significant electrolyte abnormalities including hypomagnesaemia. We explored the prevalence of PPI associated hypomagnesaemia (PPIH) in different Chronic Kidney Disease (CKD) stages, in different PPI agents, and the impact of PPIH on survival in CKD.

Methods

This was a subgroup analysis of the Salford Kidney Study, a prospective, observational, longitudinal study of non-dialysis CKD patients. Patients with outpatient magnesium samples obtained between 2002 and 2013 were included in the analysis. The prevalence hypomagnesaemia based on mean values over 12 months as well as ‘ever’ hypomagnesaemia were investigated.

Results

1,230 patients were included in this analysis, mean age 64.3± 32.3 years and mean eGFR 29.2±15.8 ml/min/1.73m². Mean serum magnesium in those on PPI was significantly lower than those not on PPI overall (0.85±0.10 mmolL^-1 versus 0.79±0.12 mmolL^-1 respectively, p<0.001). This finding was maintained at all CKD stages. The adjusted odds ratio (OR) for mean hypomagnesaemia in PPI use was 1.12 (95% CI 1.06–1.18) p = <0. ‘Ever hypomagnesaemia’ had an OR of 1.12 (95% CI 1.07–1.16) p = <0.001. The expected rise in serum magnesium with declining eGFR was not observed in those on a PPI but was seen in those not on PPI. There was no difference in serum magnesium between PPI drugs. Thiazide diuretics were also associated with hypomagnesaemia independent of PPI use. Cox regression analysis demonstrated no reduction in survival in patients with PPI associated hypomagnesaemia.

Conclusion

No specific PPI drugs show a favourable profile in regards of risk for hypomagnesaemia in CKD. Avoiding concurrent use of PPI and thiazide may be of value in patients with hypomagnesaemia.

Magnesium Counteracts Vascular Calcification: Passive Interference or Active Modulation?

Over the last decade, an increasing number of studies report a close relationship between serum magnesium concentration and cardiovascular disease risk in the general population. In end-stage renal disease, an association was found between serum magnesium and survival. Hypomagnesemia was identified as a strong predictor for cardiovascular disease in these patients. A substantial body of in vitro and in vivo studies has identified a protective role for magnesium in vascular calcification. However, the precise mechanisms and its contribution to cardiovascular protection remain unclear. There are currently 2 leading hypotheses: first, magnesium may bind phosphate and delay calcium phosphate crystal growth in the circulation, thereby passively interfering with calcium phosphate deposition in the vessel wall. Second, magnesium may regulate vascular smooth muscle cell transdifferentiation toward an osteogenic phenotype by active cellular modulation of factors associated with calcification. Here, the data supporting these major hypotheses are reviewed. The literature supports both a passive inorganic phosphate-buffering role reducing hydroxyapatite formation and an active cell-mediated role, directly targeting vascular smooth muscle transdifferentiation. However, current evidence relies on basic experimental designs that are often insufficient to delineate the underlying mechanisms. The field requires more advanced experimental design, including determination of intracellular magnesium concentrations and the identification of the molecular players that regulate magnesium concentrations in vascular smooth muscle cells.