Regulation of (Ca2+-Mg2+)-ATPase activity by calcitonin binding to rat liver plasma membranes

1985 ◽  
Vol 110 (1) ◽  
pp. 124-129 ◽  
Author(s):  
Masayoshi Yamaguchi ◽  
Michiyo Ito
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Inhibitory Effect ◽  
Maximal Inhibition ◽  
Low Concentration ◽  
High Affinity ◽  
Rat Liver Plasma Membranes

Abstract. The plasma membranes isolated from rat liver bound 125I-labelled ([125I]) synthetic [Asu1,7]eel calcitonin (CT), with increasing concentrations of [125I]CT. This specific binding was completely saturated at a concentration of 0.5 nm CT. A high affinity Ca2+ -stimulated, Mg2+-dependent ATPase [(Ca2+-Mg2+)-ATPase] activity in the plasma membranes was significantly decreased by the presence of a very low concentration of CT (7.4 pm), although the hormone did not affect the activity of the plasma membrane 5′-nucleotidase. The concentration of CT needed for maximal inhibition of (Ca2+-Mg2+)-ATPase in the plasma membranes was less than 0.74 nm. The plasma membranes washed with 10−3% digitonin did not show an inhibitory effect of CT on (Ca2+-Mg2+)-ATPase activity, while the reagent did not have a significant effect on the enzyme. These results suggest that the inhibition of (Ca2+-Mg2+)-ATPase activity maybe part of the mechanism by which CT elevates cytosolic Ca2+ in liver cells.

scholarly journals ISOLATION OF RAT LIVER PLASMA MEMBRANES

1970 ◽  
Vol 47 (3) ◽  
pp. 604-618 ◽  
Author(s):  
Oscar Touster ◽  
N. N. Aronson ◽  
John T. Dulaney ◽  
Herman Hendrickson
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Preparative Method ◽  
Membrane Localization ◽  
Plasma Membrane Localization ◽  
Liver Plasma Membranes ◽  
Nucleotide Pyrophosphatase ◽  
Rat Liver Plasma Membranes

Nucleotide pyrophosphatase and phosphodiesterase I of rat liver have been found to be localized primarily in cell particulates highly enriched with respect to the most commonly accepted plasma membrane marker, 5'-nucleotidase, and therefore should themselves be assigned a plasma membrane localization. The observation that plasma membranes sediment in isotonic sucrose with both nuclear and microsomal fractions was exploited to obtain plasma membrane preparations from each fraction. Both preparations are similar in chemical and enzymic composition. Moreover, the preparative method developed in this study appears to give the best combination of yield, purity, and reproducibility available. The question of the possible identity of nucleotide pyrophosphatase and phosphodiesterase I is considered, and evidence is presented suggesting that these activities may be manifestations of the same enzyme.

Demonstration of a high affinity Ca2+-ATPase in rat liver plasma membranes

1982 ◽  
Vol 105 (2) ◽  
pp. 488-494 ◽  
Author(s):  
Yasushi Iwasa ◽  
Takafumi Iwasa ◽  
Kenji Higashi ◽  
Kazuo Matsui ◽  
Eishichi Miyamoto
Keyword(s):  
Rat Liver ◽  
Plasma Membranes ◽  
High Affinity ◽  
Liver Plasma Membranes ◽  
Rat Liver Plasma Membranes

scholarly journals The interactions between the activatory guanine nucleotide binding protein and the catalytic subunit of adenylate cyclase in rat liver plasma membranes

1985 ◽  
Vol 231 (1) ◽  
pp. 39-46 ◽  
Author(s):  
S K-F Wong ◽  
B R Martin
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Rat Liver ◽  
Pertussis Toxin ◽  
Plasma Membranes ◽  
Binding Protein ◽  
Lag Time ◽  
Gtp Binding ◽  
Rat Liver Plasma Membranes ◽  
Maximal Extent

Three GTP-binding proteins of 50 kDa, 45 kDa and 28 kDa were identified by photoaffinity labelling with [gamma-32P]GTP-gamma-azidoanilide (A-GTP) in the rat liver plasma membrane. Pertussis toxin catalysed ADP-ribosylation of a single protein of 40 kDa. A-GTP had no effect on the basal labeling by pertussis toxin. After u.v. irradiation of the membrane in the presence of A-GTP, the GTP-dependent ADP-ribosylation by cholera toxin was increased, while the basal labelling was not affected. These results suggest that A-GTP interacts specifically with the activatory GTP-binding protein (Gs) and does not interact with the inhibitory GTP-binding protein (Gi). The effects of partial photoinactivation of Gs of the rat liver plasma membrane adenylate cyclase system by A-GTP were studied. U.v. irradiation in the presence of increasing concentrations of the analogue caused progressive decrease in the maximal extent of activation by guanosine 5′-[γ-thio]triphosphate, but the Ka was not affected. The rate of activation of liver adenylate cyclase by guanosine 5′-[γ-thio]triphosphate is temperature-dependent. The lag time increased from 0.5 min at 30 degrees C to 2.0-2.5 min at 15 degrees C in the presence of 10 microM-guanosine 5′-[γ-thio]triphosphate. However, Ka remains unaffected by lowering the temperature. Photoinactivation by A-GTP or competitive inhibition by guanosine 5′-[β-thio]diphosphate decreases the maximal extent of activation by guanosine 5′-[γ-thio] triphosphate, but the lag time remains unaffected. The present results support the idea that Gs is tightly associated with the catalytic subunit under basal conditions. The present results also indicate that the transition of an inactive Gs to its active form is the rate-limiting step of the activation of adenylate cyclase by guanosine 5′-[γ-thio]triphosphate in the intact rat liver plasma membranes.

scholarly journals Alkaline ribonuclease and phosphodiesterase activity in rat liver plasma membranes

1973 ◽  
Vol 132 (3) ◽  
pp. 449-458 ◽  
Author(s):  
Terence D. Prospero ◽  
Malcolm L. E. Burge ◽  
Kenneth A. Norris ◽  
Richard H. Hinton ◽  
Eric Reid
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Gradient Centrifugation ◽  
Ribonuclease Activity ◽  
Nuclear Fraction ◽  
Phosphodiesterase Activity ◽  
Ph Optimum ◽  
Liver Plasma Membranes ◽  
Rat Liver Plasma Membranes

The ribonuclease and phosphodiesterase activities of rat liver plasma membranes, purified from the crude nuclear fraction by centrifugation in an A-XII zonal rotor and flotation, were examined and compared. The plasma membrane is responsible for between 65 and 90% of the phosphodiesterase activity of the cell and between 25 and 30% of the particulate ribonuclease activity measured at pH8.7 in the presence of 7.5mm-MgCl2. Both enzymes were most active between pH8.5 and 8.9. Close to the pH optimum, both enzymes were more active in Tris buffer than in Bicine or glycine buffer. Both plasma-membrane phosphodiesterase and ribonuclease were strongly activated by Mg2+, there being at least a 12-fold difference between the activity in the presence of Mg2+ and of EDTA. There is, however, a difference in the response of the enzymes to Mg2+ and EDTA in that the phosphodiesterase is fully activated by 1.0mm-MgCl2 and fully inhibited by 1.0mm-EDTA, whereas the ribonuclease requires 7.5mm-MgCl2 for full activation and 5mm-EDTA for full inhibition. Density-gradient centrifugation has indicated that on solubilization in Triton X-100 most of the ribonuclease activity is released into a small fragment of the same size as that containing the phosphodiesterase activity. The relationship between the two activities is discussed in view of these results.

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