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Biomedical subjects

E T Wallick

Publications and source records attributed to E T Wallick.

At least 55 records · Page 3Linked to original sources
PubMed1977

Modification of (Na+,K+)-ATPase function by purified antibodies to the holoenzyme. Effects on enzyme activity and (3H)ouabain binding.

Antibodies (abys) raised to (Na+,K+)-ATPase were purified by elution methods and shown to be cross-reactive with anti-gamma-globulin and the original antigen. Abys were isolated from two different antisera and the effects on (Na+,K+)-ATPase hydrolytic activity and [3H]ouabain binding were measured. The antisera fractions differed as to their maximum level of inhibition of hydrolytic activity and maximal [3H]ouabain binding, but both fractions caused inhibition of maximal [3H]ouabain binding to the same quantitative extent as inhibition of hydrolytic activity. Variable effects on the rate of [3H]ouabain binding were noted which were highly dependent on ligand conditions. During the "turnover state conditions" of the enzyme, the abys stimulated the rate of [3H]ouabain binding to the (Na+,K+)-ATPase. We conclude that effects of aby-(Na+,K+)-ATPase interaction depend upon degree of purity of aby, specificity, aby/enzyme ratios, and ligand conditions.

Adenosine Triphosphatases↗
PubMed1977

The effect of palmitoyl-coenzyme A on rat heart and liver mitochondria. Oxygen consumption and palmitoylcarnitine formation.

Rat heart and liver mitochondria, respectively, oxidized palmitoyl-CoA and palmitoylcarnitine optimally at 20-30 and 10-20 nmol substrate/mg. The oxidation of palmitoyl-CoA was accompanied by a lag in State 3 respiration that was proportional to the palmitoyl-CoA concentration. The delay in State 3 rates was more prolonged in liver than in heart at comparable palmitoyl-CoA levels. A similar range of palmitoyl-CoA concentrations produced significant inhibition of respiration in mitochondria oxidizing glutamate-malate. The inhibition was not due to a detergent effect of palmitoyl-CoA since addition of carnitine restored State 3 rates. Electron microscopic examination of mitochondria at low palmitoyl-CoA levels revealed normal ultrastructure. At comparable concentrations of palmitoyl-CoA, formation of palmitoylcarnitine by mitochondria from rat heart and liver followed first-order kinetics. The apparent first-order rate constants decreased with increasing palmitoyl-CoA. These results suggest that substrate inhibition may influence the rate of palmitoyl carnitine formation even at physiological concentrations of palmitoyl-CoA. The apparent first-order rate constant at palmitoyl-CoA levels (12 nmol palmitoyl CoA/mg) optimally oxidized by liver mitochondria, was one-third the value of the apparent rate constant measured in heart mitochondria at the identical substrate level. The prolongation in time to reach equilibrium may acocunt for the relatively greater respiratory sensitivity of liver mitochondria to increasing levels of palmitoyl-CoA.

Animals↗
PubMed1977

Recent advances in cardiac glycoside-Na+,K+-ATPase interaction.

Na+,K+-ATPase has been purified from lamb kidney and consists of two polypeptide peaks on polyacrylamide gel electrophoresis with an enzyme activity of 1,000 mumole Pi/mg pro per hr. A scheme depicting the interaction of cardiac glycoside with the enzyme and ligand effects on binding has been constructed. Under all ligand conditions, ouabain binding tends to reach the same maximum if sufficient ouabain is present. Initial rates vary with ligand conditions. Using a chase method, the rate of dissociation of the glycoside from the enzyme is not influenced by the ligands present, although with separation of the enzyme-glycoside complex from the binding medium, differences are noted. The effect of ouabain on Na binding demonstrated two classes of sites, KD = 0.2 mM and KD = 18 mM. Denaturation decreased the high affinity sites. There was also a good correlation between ouabain binding and inhibition of Na binding. Clearly, ligands are critical in regulating cardiac glycoside interaction with the enzyme.

Adenosine Triphosphatases↗
PubMed1976

Specific sodium-22 binding to a purified sodium + potassium adenosine triphosphatase. Inhibition by ouabain.

Analysis of sodium-22 binding to purified sodium + potassium ion-activated adenosine triphosphatase (Na+, K+)-ATPase reveals the presence of two classes of binding sites. The higher affinity site (Kd = 0.2 mM) binds 6 to 7 nmol of sodium per mg of protein. Pretreatment of (Na+, K+)-ATPase with ouabain blocks the binding of sodium to this higher affinity site. Neither heat-denatured enzyme nor phospholipids extracted from the (Na+, K+)-ATPase contain a ouabain-inhibitable, higher affinity sodium binding site. The ouabain enzyme complex therefore appears to contain altered binding sites for cations.

Adenosine Triphosphatases↗
PubMedDate not supplied

Canine mesenteric artery Na+,K+-ATPase: vasopressor receptor for digitalis?

Localization and characterization studies of Na+,K+-ATPase in canine superior mesenteric artery were undertaken to examine the role of the Na+-K+ pump in the vasopressor response of cardiac glycosides. The enzymatic component of the membrane-bound Na+-K+ pump, Na+,K+-ATPase, was found by histochemical and cell fractionation techniques to be localized primarily in the sarcolemma of the smooth muscle cell in superior mesenteric artery. The enzyme could be enriched in microsomal and partially purified sarcolemma preparations of superior mesenteric artery and first-order arterial side branches. Binding of [3H]ouabain to arterial microsomes followed pseudo-first-order reaction kinetics. In the presence of magnesium plus ATP, sodium stimulates and potassium inhibits the rate of binding. Scatchard analysis indicated a single class of [3H]ouabain binding sites with a KD of 2-9 nM and a Bmax of 2.3-3.5 pmol/mg protein. Although the characteristics of [3H]ouabain binding to mesenteric artery microsomes resemble the characteristics of [3H]ouabain binding to purified Na+,K+-ATPase, the density or total number of Na+-K+ pump sites in mesenteric artery is small compared with either heart muscle or kidney parenchyma. In isolated mesenteric arterial strips, more than 80% of a 2.5 microM ouabain-induced contraction could be inhibited or reversed by alpha-adrenoceptor blockade with 1 microM phentolamine. These data indicate that although cardiac glycosides interact with specific receptor sites in smooth muscle of canine superior mesenteric artery, the direct vasoconstrictor effect, which may be related to this digitalis-smooth muscle Na+,K+-ATPase interaction, is meager and may be a reflection of the low density of Na+-K+ pump sites.

Animals↗