Magnesium Adenosine Triphosphate Research Articles

A METHOD FOR THE CYTOCHEMICAL DEMONSTRATION OF SODIUM-ACTIVATED ADENOSINE TRIPHOSPHATASE.

(1) In the histochemical method for adenosine triphosphatase, when magnesium and ATP are in equivalent concentrations, and sodium is present in the medium, staining occurs in the tissues. When sodium is omitted from this medium some structures—previously stained in the presence of sodium—fail to stain. (2) Ouabain inhibits staining when magnesium and ATP are equivalent and sodium is present in the medium. (3) The effects of calcium, potassium and sodium on staining with the proposed medium parallel the effects of these ions on activity of sodium-activated ATPase in vitro. (4) When magnesium ions and ATP are not equivalent in the substrate, sodium and ouabain fail to affect staining. (5) Certain tissue structures—such as the axonic nerve ending—which have been shown to contain sodium-activated ATPase in vitro, stain in the presence of sodium when magnesium and ATP are equivalent, but fail to stain when sodium is omitted from this medium.

Ameboid movement: I. Reactivation of glycerinated models of Amoeba proteus with adenosinetriphosphate

A modified glycerol extraction and reactivation procedure was devised for the preparation of Amoeba proteus models. These models contract in the presence of magnesium ions and ATP, and their general behavior resembles that of the muscular models. Compared to the usual procedures of preparation of muscular and cellular models, the most important modifications consist in the use of a preliminary treatment of the live amoebae with a dilute solution of EDTA, a gradual extraction with glycerol and the use of a low ionic strength (0.05) for all the solutions.

Thyroxine and the release of protein from rat liver mitochondria.

Thyroactive compounds at concentrations down to 5 × 10−6 M have the property of decreasing the amount of protein released by rat liver mitochondria in a suspending medium of either sucrose or phosphate at pH 7.4. This reaction is marked after 30 minutes at 37 C but is detectable at 25 C. A small amount of protein is released during the phase of rapid swelling produced by thyroid hormones, but thereafter the protein content of the suspending medium remains almost constant. By contrast, the delayed swelling noted in solvent controls is accompanied by continuous release of larger amounts of protein. Both magnesium ions and ATP at high concentrations affect the reaction in a complex manner, decreasing the release of protein in the solvent controls, an effect that is antagonized by the thyronines. These findings may be related to the preservation by thyronines of the failing metabolic systems of isolated tissues.

The demonstration of adenosinetriphosphatase activity with the electronmicroscope.

A new method for the demonstration of adenosine triphosphatase (ATP'ase) activity in tissue blocks with the electron-microscope has been developed. This method consists of short fixation (2–3 minutes,ph 7.3) in a OsO4-Tris-HCl mixture, incubation with a medium containing Tris-HCl buffer, tartrate, lead and magnesium ions, ATP and sucrose (ph 6.8) and routine postfixation. The method combines satisfactory histochemical specificity with good preservation of tissue fine structure. Estimations of enzymatic activity of ATP'ase and alkaline phosphatase, as observed with the electronmicroscope, were compared with activity determinations in tissue homogenates. The occurence of a positive histochemical reaction in swollen mitochondria is discussed.

Effect of adenosine triphosphate, magnesium, and calcium on the phosphate uptake by rabbit erythrocytes

1. 1. The addition of adenosine triphosphate (ATP) to rabbit erythrocytes in vitro stimulated the uptake of labelled orthophosphate ions. 2. 2. The addition of calcium or magnesium ions alone inhibited phosphate uptake when the concentrations of Ca, Mg, and phosphate were approximately equal. 3. 3. The addition of both magnesium ions and ATP had a variable effect on phosphate uptake ranging from inhibition, when the concentrations of phosphate and magnesium were approximately equal, to stimulation when the concentration of ATP was greater or less than that of Mg. 4. 4. An attempt has been made to explain these observations on the basis of the known effects of ATP on the solubility of divalent alkaline metal phosphates and the possible interactions which might occur in a system including ATP, Mg and phosphate ions.

Kidney Citrate Levels in Nucleotide Shock

DURING recent studies on carbohydrate metabolism in shock, we have examined the citrate-level in the kidney of the fasting rat by Buffa and Peters's modification1 of the method of Pucher, Sherman and Vickery2, during the shock state produced by the parenteral injection of nucleotides. A marked increase (P = 0.01) in the citrate content of the kidney occurred 1 hr. after the intraperitoneal injection of a lethal dose of adenosinetriphosphate (250 mgm. magnesium adenosinetriphosphate per 100 gm. body-weight in the strain of rat used, at an environmental temperature of 18–22° C.; see table). This increase was not maintained, and 4 hr. after the injection the level had returned to normal. In its time relationships this effect resembles that seen in fluoro-acetate poisoning; but in the latter condition the increase in the citrate content of the rat kidney is much greater1,3.