Image analysis of the histochemical demonstration of glucose-6-phosphatase activity in rat liver

1986 ◽  
Vol 86 (2) ◽  
pp. 181-190 ◽  
Author(s):  
R. Hildebrand ◽  
A. Schleicher
Keyword(s):  
Image Analysis ◽  
Phosphatase Activity ◽  
Rat Liver ◽  
Histochemical Demonstration

scholarly journals CYTOPHOTOMETRIC QUANTITATION OF GLUCOSE 6-PHOSPHATASE ACTIVITY IN RAT LIVER

1969 ◽  
Vol 17 (2) ◽  
pp. 107-109 ◽  
Author(s):  
D. E. ABRAHAMSON ◽  
J. L. RIGATUSO ◽  
A. LAZAROW
Keyword(s):  
Phosphatase Activity ◽  
Rat Liver ◽  
Optical Density ◽  
Incubation Time ◽  
Specific Inhibitor ◽  
Histochemical Demonstration ◽  
Precipitation Method ◽  
Normal Tissues ◽  
Fresh Frozen ◽  
Normal Rat

The Wachstein-Meisel lead sulfide precipitation method was used for the histochemical demonstration of glucose 6-phosphatase activity in fresh-frozen normal rat liver sections. Transmittances, microspectrophotometrically determined over cytoplasmic areas of stained sections, were used to calculate the optical density of the stain. In spite of the fact that no absorption maximum was found, the spectrum of glucose 6-phosphatase stain showed proportional increases with increased incubation time. The extinction at a fixed wavelength was shown to be a linear function of incubation time. Studies in which normal tissues were incubated in buffer-substrate and then removed and reincubated for an additional period of time in buffer-substrate containing a specific inhibitor of glucose 6-phosphatase indicate that the increase in optical density of the stain was a result of glucose 6-phosphatase activity.

scholarly journals Protein histidine phosphatase activity in rat liver and spinach leaves

FEBS Letters ◽  
1995 ◽  
Vol 364 (1) ◽  
pp. 51-54 ◽  
Author(s):  
Harry R. Matthews ◽  
Carol MacKintosh
Keyword(s):  
Phosphatase Activity ◽  
Rat Liver ◽  
Spinach Leaves

scholarly journals Insulin-receptor phosphotyrosyl-protein phosphatases

1988 ◽  
Vol 256 (3) ◽  
pp. 893-902 ◽  
Author(s):  
M J King ◽  
G J Sale
Keyword(s):  
Insulin Receptor ◽  
Phosphatase Activity ◽  
Rat Liver ◽  
Protein Phosphatase ◽  
Egf Receptor ◽  
Soluble Fraction ◽  
Protein Phosphatases ◽  
Egf Receptors ◽  
Cell Extracts ◽  
Dependent Protein

Calmodulin-dependent protein phosphatase has been proposed to be an important phosphotyrosyl-protein phosphatase. The ability of the enzyme to attack autophosphorylated insulin receptor was examined and compared with the known ability of the enzyme to act on autophosphorylated epidermal-growth-factor (EGF) receptor. Purified calmodulin-dependent protein phosphatase was shown to catalyse the complete dephosphorylation of phosphotyrosyl-(insulin receptor). When compared at similar concentrations, 32P-labelled EGF receptor was dephosphorylated at greater than 3 times the rate of 32P-labelled insulin receptor; both dephosphorylations exhibited similar dependence on metal ions and calmodulin. Native phosphotyrosyl-protein phosphatases in cell extracts were also characterized. With rat liver, heart or brain, most (75%) of the native phosphatase activity against both 32P-labelled insulin and EGF receptors was recovered in the particulate fraction of the cell, with only 25% in the soluble fraction. This subcellular distribution contrasts with results of previous studies using artificial substrates, which found most of the phosphotyrosyl-protein phosphatase activity in the soluble fraction of the cell. Properties of particulate and soluble phosphatase activity against 32P-labelled insulin and EGF receptors are reported. The contribution of calmodulin-dependent protein phosphatase activity to phosphotyrosyl-protein phosphatase activity in cell fractions was determined by utilizing the unique metal-ion dependence of calmodulin-dependent protein phosphatase. Whereas Ni2+ (1 mM) markedly activated the calmodulin-dependent protein phosphatase, it was found to inhibit potently both particulate and soluble phosphotyrosyl-protein phosphatase activity. In fractions from rat liver, brain and heart, total phosphotyrosyl-protein phosphatase activity against both 32P-labelled receptors was inhibited by 99.5 +/- 6% (mean +/- S.E.M., 30 observations) by Ni2+. Results of Ni2+ inhibition studies were confirmed by other methods. It is concluded that in cell extracts phosphotyrosyl-protein phosphatases other than calmodulin-dependent protein phosphatase are the major phosphotyrosyl-(insulin receptor) and -(EGF receptor) phosphatases.

scholarly journals Fatty acyl-CoA esters inhibit glucose-6-phosphatase in rat liver microsomes

1995 ◽  
Vol 307 (2) ◽  
pp. 391-397 ◽  
Author(s):  
R Fulceri ◽  
A Gamberucci ◽  
H M Scott ◽  
R Giunti ◽  
A Burchell ◽  
...  
Keyword(s):  
Palmitic Acid ◽  
Phosphatase Activity ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Fatty Acyl ◽  
Rat Liver Microsomes ◽  
Control Value ◽  
Scattering Measurements ◽  
Induced Changes ◽  
Enzymic Assay

In native rat liver microsomes glucose 6-phosphatase activity is dependent not only on the activity of the glucose-6-phosphatase enzyme (which is lumenal) but also on the transport of glucose-6-phosphate, phosphate and glucose through the respective translocases T1, T2 and T3. By using enzymic assay techniques, palmitoyl-CoA or CoA was found to inhibit glucose-6-phosphatase activity in intact microsomes. The effect of CoA required ATP and fatty acids to form fatty acyl esters. Increasing concentrations (2-50 microM) of CoA (plus ATP and 20 microM added palmitic acid) or of palmitoyl-CoA progressively decreased glucose-6-phosphatase activity to 50% of the control value. The inhibition lowered the Vmax without significantly changing the Km. A non-hydrolysable analogue of palmitoyl-CoA also inhibited, demonstrating that binding of palmitoyl-CoA rather than hydrolysis produces the inhibition. Light-scattering measurements of osmotically induced changes in the size of rat liver microsomal vesicles pre-equilibrated in a low-osmolality buffer demonstrated that palmitoyl-CoA alone or CoA plus ATP and palmitic acid altered the microsomal permeability to glucose 6-phosphate, but not to glucose or phosphate, indicating that T1 is the site of palmitoyl-CoA binding and inhibition of glucose-6-phosphatase activity in native microsomes. The type of inhibition found suggests that liver microsomes may comprise vesicles heterogeneous with respect to glucose-6-phosphate translocase(s), i.e. sensitive or insensitive to fatty acid ester inhibition.

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