Hormone-stimulated Mg2+ accumulation into rat hepatocytes: a pathway for rapid Mg2+ and Ca2+ redistribution

Fagan, Theresa E.; Scarpa, Antonio

doi:10.1016/s0003-9861(02)00051-6

Cited by 8 publications

(3 citation statements)

References 32 publications

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“…A major difference can be noticed in hepatocytes from fed vs. starved rats. Consistent with previous reports (7,35), fed hepatocytes accumulate Mg 2ϩ almost exclusively via what appears to be an Na ϩ -dependent mechanism, as indicated by the Na ϩ removal and imipramine data, whereas variations in extracellular glucose enlarge the amplitude of Mg 2ϩ accumulation by 10 -15% at the most. Yet, as mentioned previously, the Na ϩ electrochemical gradient across the cell membrane makes unlikely that Mg 2ϩ entry occurs via the reverse operation of the Na ϩ /Mg 2ϩ exchanger, as observed in plasma membrane vesicles isolated from the basolateral domain of the hepatocyte (2).…”

Section: Discussionsupporting

confidence: 92%

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Role of glucose in modulating Mg²⁺homeostasis in liver cells from starved rats

Torres

Youngner

Romani

2005

American Journal of Physiology-Gastrointestinal and Liver Physi

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α1- and β-Adrenoceptor stimulation elicits Mg2+ extrusion from liver cells in conjunction with hepatic glucose output (T. Fagan and A. Romani. Am J Physiol Gastrointest Liver Physiol 279: G943–G950, 2000.). To characterize the role of intrahepatic glucose on Mg2+ transport, male Sprague-Dawley rats were starved overnight before being anesthetized and used as organ donors. Perfused livers or collagenase-dispersed hepatocytes were stimulated by α1 (phenylephrine)- or β (isoproterenol)-adrenergic agonists. Mg2+ extrusion was assessed by atomic absorbance spectrophotometry. In both experimental models, the administration of pharmacological doses of adrenergic agonists did not elicit Mg2+ extrusion. The determination of cellular Mg2+ indicated an ∼9% decrease in total hepatic Mg2+ content in liver cells after overnight fasting, whereas the ATP level was unchanged. Hepatocytes from starved rats accumulated approximately four times more Mg2+ than liver cells from fed animals. This enlarged Mg2+ accumulation depended in part on extracellular glucose, since it was markedly reduced in the absence of extracellular glucose or in the presence of the glucose transport inhibitor phloretin. The residual Mg2+ accumulation observed in the absence of extracellular glucose was completely abolished by imipramine or removal of extracellular Na+. Taken together, these data indicate 1) that hepatic glucose mobilization is essential for Mg2+ extrusion by adrenergic agonist and 2) that starved hepatocytes accumulate Mg2+ via two distinct pathways, one of which is associated with glucose transport, whereas the second can be tentatively identified as an imipramine-inhibited Na+-dependent pathway.

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Section: Discussionsupporting

confidence: 92%

“…A little more uncertainty exists about the pathway used for Mg 2ϩ accumulation. Also, this process appears to require a physiological concentration of Na ϩ (35) but not Ca 2ϩ (7) in the extracellular milieu. Yet, the intrinsic nature of the transport mechanism remains undefined.…”

Section: Discussionmentioning

confidence: 99%

Role of glucose in modulating Mg²⁺homeostasis in liver cells from starved rats

Torres

Youngner

Romani

2005

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…The liver was chosen as targeted tissue for this analysis since it plays a major role in Mg homeostasis [4] and it regulates many metabolic pathways, including glucose, xenobiotics and steroid hormone metabolisms. Moreover, only few studies have reported on the impact of Mg deficiency on liver [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

N-Acetylcysteine Partially Reverses Oxidative Stress and Apoptosis Exacerbated by Mg-Deficiency Culturing Conditions in Primary Cultures of Rat and Human Hepatocytes

Martin¹,

Abadie²,

Heyd³

et al. 2006

Journal of the American College of Nutrition

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Our results indicate that Mg deficiency exacerbates the rate of apoptosis in cultured hepatocytes, associated with an increase in oxidative stress, the sensitivity of human hepatocytes being equivalent to that of rat hepatocytes. They also indicate a dual role of NAC and/or GSH, i.e. protective for hepatocytes placed in a Mg-deficient environment, while deleterious for hepatocytes placed in a Mg-physiological environment.

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Mg2+ release coupled to Ca2+ uptake: A novel Ca2+ accumulation mechanism in rat liver

Cefaratti

2006

Mol Cell Biochem

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Isolated hepatocytes release 2-3 nmol Mg2+/mg protein or approximately 10% of the total cellular Mg2+ content within 2 minutes from the addition of agonists that increase cellular cAMP, for example, isoproterenol (ISO). During Mg2+ release, a quantitatively similar amount of Ca2+ enters the hepatocyte, thus suggesting a stoichiometric exchange ratio of 1 Mg2+:1Ca2+. Calcium induced Mg2+ extrusion is also observed in apical liver plasma membranes (aLPM), in which the process presents the same 1 Mg2+:1Ca2+ exchange ratio. The uptake of Ca2+ for the release of Mg2+ occurs in the absence of significant changes in Deltapsi as evidenced by electroneutral exchange measurements with a tetraphenylphosphonium (TPP+) electrode or 3H-TPP+. Collapsing the Deltapsi by high concentrations of TPP+ or protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) does not inhibit the Ca2+-induced Mg2+ extrusion in cells or aLPM. Further, the process is strictly unidirectional, serving only in Ca2+ uptake and Mg2+ release. These data demonstrate the operation of an electroneutral Ca2+/Mg2+ exchanger which represents a novel pathway for Ca2+ accumulation in liver cells following adrenergic receptor stimulation.

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Hormone-stimulated Mg2+ accumulation into rat hepatocytes: a pathway for rapid Mg2+ and Ca2+ redistribution

Cited by 8 publications

References 32 publications

Role of glucose in modulating Mg²⁺homeostasis in liver cells from starved rats

Role of glucose in modulating Mg²⁺homeostasis in liver cells from starved rats

N-Acetylcysteine Partially Reverses Oxidative Stress and Apoptosis Exacerbated by Mg-Deficiency Culturing Conditions in Primary Cultures of Rat and Human Hepatocytes

Mg2+ release coupled to Ca2+ uptake: A novel Ca2+ accumulation mechanism in rat liver

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Hormone-stimulated Mg2+ accumulation into rat hepatocytes: a pathway for rapid Mg2+ and Ca2+ redistribution

Cited by 8 publications

References 32 publications

Role of glucose in modulating Mg2+homeostasis in liver cells from starved rats

Role of glucose in modulating Mg2+homeostasis in liver cells from starved rats

N-Acetylcysteine Partially Reverses Oxidative Stress and Apoptosis Exacerbated by Mg-Deficiency Culturing Conditions in Primary Cultures of Rat and Human Hepatocytes

Mg2+ release coupled to Ca2+ uptake: A novel Ca2+ accumulation mechanism in rat liver

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Role of glucose in modulating Mg²⁺homeostasis in liver cells from starved rats

Role of glucose in modulating Mg²⁺homeostasis in liver cells from starved rats