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The abundance of magnesium (Mg2+) within mammalian cells is consistent with its relevant role in regulating tissue and cell functions. At the last count, more than three hundred and fifty enzymes, aside from metabolic cycles, appear to require and be regulated by concentrations of Mg2+ that are well within the physiological range observed in tissues and(More)
Upon activation of specific cell signaling, hepatocytes rapidly accumulate or release an amount of Mg(2+) equivalent to 10% of their total Mg(2+) content. Although it is widely accepted that Mg(2+) efflux is Na(+)-dependent, little is known about transporter identity and the overall regulation. Even less is known about the mechanism of cellular Mg(2+)(More)
The plasma membrane of mammalian cells possesses rapid Mg2+ transport mechanisms. The identity of Mg2+ transporters is unknown, and so are their properties. In this study, Mg2+ transporters were characterized using a biochemically and morphologically standardized preparation of sealed rat liver plasma membranes (LPM) whose intravesicular content could be(More)
The effect of the transmembrane potential (delta psi) and the proton concentration gradient (delta pH) across the chromaffin granule membrane upon the rate and extent of catecholamine accumulation was studied in isolated bovine chromaffin granules. Freshly isolated chromaffin granules had an intragranular pH of 5.5 as measured by [14C]methylamine(More)
Values for ionized [Ca] in squid axons were obtained by measuring the light emission from a 0.1-mul drop of aequorin confined to a plastic dialysis tube of 140-mum diameter located axially. Ionized Ca had a mean value of 20 x 10(-9) M as judged by the subsequent introduction of CaEGTA/EGTA buffer (ratio ca. 0.1) into the axoplasm, and light measurement on a(More)
Perfused rat hearts release or accumulate approximately 10% of total Mg2+ content when stimulated with norepinephrine (NE) or carbachol, respectively. Collagenase-dispersed rat ventricular myocytes increase or decrease total cell Mg2+ by 1 mM within 5 minutes when stimulated with these same transmitters. Measurements of Mg2+ transport using 28Mg or atomic(More)
The changes in total Mg were compared with changes in cytosolic free Mg(2+) during metabolic stimulation of collagenase-dispersed rat cardiac myocytes or Langendorff-perfused rat hearts. In myocytes the addition of agents leading to cAMP increase or protein kinase C activation results in a loss or gain of more than 5% of total Mg content within 3 min (i.e.,(More)
Inactivation of a dihydropyridine-sensitive calcium current was studied in a cell line (A7r5) derived from smooth muscle of the rat thoracic aorta. Inactivation is faster with extracellular Ca2+ than with Ba2+. In Ba2+, inactivation increases monotonically with depolarization. In Ca2+, inactivation is related to the amount of inward current, so that little(More)
A 1-month-old boy was admitted because of failure to thrive. He was floppy and had bilateral ptosis, diminished reflexes, and poor suck. He had aspiration pneumonia, developed seizures, and died at age 3 1/2 months. Laboratory data showed lactic acidosis, proteinuria, glycosuria and generalized aminoaciduria. He was an only child, and family history was(More)