scholarly journals A study of stabilization of gluconeogenic activity in rat liver slices by calcium and manganese ions

1972 ◽  
Vol 129 (2) ◽  
pp. 231-239 ◽  
Author(s):  
Anne Roobol ◽  
G. A. O. Alleyne
Keyword(s):  
Rat Liver ◽  
Phosphoenolpyruvate Carboxylase ◽  
Incubation Medium ◽  
Lysosomal Enzymes ◽  
Glucose Production ◽  
Liver Slice ◽  
Manganese Ions ◽  
Slice Preparation ◽  
Carboxylase Activity ◽  
Bivalent Cations

1. The effect of some bivalent cations on gluconeogenesis by the rat liver-slice preparation has been investigated. 2. Ca2+and Mn2+stimulated glucose production from a range of substrates but not from glycerol. Mg2+had no effect on the rate of glucose production. 3. Ca2+were required to maintain phosphoenolpyruvate carboxylase activity in the slice preparation. 4. Ca2+and Mn2+, but not Mg2+, retarded the release of lysosomal enzymes from the slice into the incubation medium. 5. It is proposed that Ca2+and Mn2+stimulate glucose production by stabilizing the lysosome system in the liver-slice preparation. 6. The value of the liver-slice preparation as a means of measuring hepatic gluconeogenesis is discussed.

scholarly journals Effect of micromolar concentrations of manganese ions on calcium-ion cycling in rat liver mitochondria

1983 ◽  
Vol 212 (3) ◽  
pp. 773-782 ◽  
Author(s):  
B P Hughes ◽  
J H Exton
Keyword(s):  
Rat Liver ◽  
Calcium Ion ◽  
Incubation Medium ◽  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Rat Liver Mitochondria ◽  
Manganese Ions ◽  
Dose Dependent Decrease ◽  
Incubation Temperatures ◽  
Dose Dependent

The effects of micromolar concentrations of Mn2+ on the rat liver mitochondrial Ca2+ cycle were investigated. It was found that the addition of Mn2+ to mitochondria which were cycling 45Ca2+ led to a rapid dose dependent decrease in the concentration of extramitochondrial 45Ca2+ of about 1 nmol/mg of protein. The effect was complete within 30 s, was half maximal with 10 microM Mn2+ and was observed in the presence of 3 mM Mg2+ and 1 mM ATP. It occurred over a broad range of incubation temperatures, pH and mitochondrial Ca2+ loads. It was not observed when either Mg2+ or phosphate was absent from the incubation medium, or in the presence of Ruthenium Red. These findings indicate that micromolar concentrations of Mn2+ stimulate the uptake of Ca2+ by rat liver mitochondria, and provide evidence for an interaction between Mg2+ and Mn2+ in the control of mitochondrial Ca2+ cycling.

scholarly journals Mechanisms of loss of latency of lysosomal enzymes. Effects of incubation on the properties of lysosomal membranes

1980 ◽  
Vol 186 (1) ◽  
pp. 243-256 ◽  
Author(s):  
R C Ruth ◽  
W B Weglicki
Keyword(s):  
Rat Liver ◽  
Incubation Medium ◽  
Lysosomal Enzymes ◽  
Fragility Curves ◽  
Osmotic Fragility ◽  
Lysosomal Membrane ◽  
Assay Medium ◽  
Additional Amount ◽  
Before And After ◽  
Free Activity

1. The effects of sucrose and KCl on the loss of latency of lysosomal enzymes caused by incubation at 37 degrees C, pH 7.4, were examined by using Triton-filled lysosomes from rat liver and two fractions from livers of rats not injected with Triton. 2. After incubation, the percentage free activity of lysosomal enzymes was measured before and after cooling to 0 degrees C in order to determine the amount of latency lost at 37 degrees C without cooling and the additional amount lost on cooling the incubated lysosomes to 0 degrees C. 3. The latency that is lost without cooling is first decreased and then increased by increasing the osmotic strength of the incubation medium with KCl, or with sucrose in the presence of KCl. However, if the osmotic strength is increased with sucrose alone, loss of latency is decreased up to 0.25M-sucrose, but is increased only slightly at higher sucrose concentrations. Apparently the lysosome is permeated by hyperosmolar KCl but not by sucrose during incubation. 4. If the osmotic strength of the assay medium is increased with KCl, the loss of latency caused by incubation for 60 min in hyperosmolar KCl is repressed. Thus it appears that a KCl-permeated lysosome can be obtained which is relatively stable until exposure to lower osmolarities. 5. The loss of latency caused by cooling incubated lysosomes to 0 degrees C is largely eliminated if the osmotic strength of the medium in which the lysosomes are cooled is raised sufficiently with either sucrose or KCl. 6. Osmotic-fragility curves were obtained after incubation for 1 and 60 min at iso-osmoticity (0.2M-KCl or 0.25 M-sucrose). Although little loss of latency occurs at iso-osmoticity, lysosomes incubated for 60 min display greatly increased fragility on exposure to hypo-osmolar KCl, hypo-osmolar sucrose or hyperosmolar KCl. 7. It is suggested that permeability to KCl at 37 degrees C and the increase in fragility on exposure to hypo-osmolar conditions are both consequences of injury, probably from enzymic action, sustained by the lysosomal membrane during incubation at 37 degrees C.

scholarly journals Transformation of the glucocorticoid receptor in rat liver cytosol by lysosomal enzymes.

1979 ◽  
Vol 254 (5) ◽  
pp. 1537-1539 ◽  
Author(s):  
J. Carlstedt-Duke ◽  
O. Wrange ◽  
E. Dahlberg ◽  
J.A. Gustafsson ◽  
B. Högberg
Keyword(s):  
Glucocorticoid Receptor ◽  
Rat Liver ◽  
Lysosomal Enzymes ◽  
Liver Cytosol ◽  
Rat Liver Cytosol

Regulation of glucagon-stimulated production of glucose in rat liver by guanosine 3′,5′-cyclic phosphate

1976 ◽  
Vol 54 (6) ◽  
pp. 834-837 ◽  
Author(s):  
Richard M. Epand ◽  
Connie Prosser
Keyword(s):  
Rat Liver ◽  
Guanylate Cyclase ◽  
Glucose Production ◽  
Liver Slices ◽  
Cyclic Phosphate ◽  
Camp And Cgmp

Exogenous cGMP can inhibit both basal and glucagon-stimulated production of glucose in liver slices from fed rats. Thus, cAMP and cGMP have opposite effects on the production of glucose in rat liver. Acetylcholine, an activator of guanylate cyclase (EC 4.6.1.2) in other systems, also inhibits the glucagon-stimulated production of glucose. No effect on glucose production was observed with secretin or exogenous GTP.

Pharmacologic perturbation of rat liver lysosomes: Effects on release of lysosomal enzymes and of lipids into bile

1988 ◽  
Vol 95 (4) ◽  
pp. 1088-1098 ◽  
Author(s):  
Richard B. Sewell ◽  
Susan A. Grinpukel ◽  
Alan R. Zinsmeister ◽  
Nicholas F. LaRusso
Keyword(s):  
Rat Liver ◽  
Lysosomal Enzymes ◽  
Liver Lysosomes ◽  
Rat Liver Lysosomes

Autoregulation of 3, 3′,5′-triiodothyronine production by rat liver microsomes

1981 ◽  
Vol 98 (2) ◽  
pp. 240-245 ◽  
Author(s):  
T. Kaminski ◽  
J. Köhrle ◽  
R. Ködding ◽  
R.-D. Hesch
Keyword(s):  
Rat Liver ◽  
Incubation Medium ◽  
Liver Microsomes ◽  
Inhibitory Effect ◽  
Incubation Mixture ◽  
Rat Liver Microsomes ◽  
Experimental Conditions ◽  
Physiological Concentration ◽  
Enzyme Binding ◽  
Ph Dependent

Abstract. Conversion of thyroxine (T4) to 3,3′,5′-triiodothyronine (rT3) was studied in rat liver microsomes. Addition of rT3 at a physiological concentration to the incubation medium inhibited the deiodination of thyroxine to rT3. With a concentration of rT3 greater than 37.6 nM no net rT3 production at pH 8.0 was observed. Further increases in rT3 concentration resulted only in degradation of added rT3 and no net synthesis of rT3 from T4 could be detected. The inhibitory effect of rT3 upon its own production from T4 was pH dependent, 5 fold lower amounts of hormone being required to inhibit completely rT3 production at pH 7.4 than at pH 8.0. With the same experimental conditions no significant effect of rT3 on the conversion of T4 to 3,5,3′-triiodothyronine (T3) could be observed at pH 8.0 with all concentrations of added iodothyronine. A linear production of 3,3′-T2 from added rT3 was determined over the whole range of rT3 concentration, suggesting a lack of saturation of deiodinating enzyme. Binding of rT3 by anti-rT3 antibody added to the incubation mixture enhanced rT3 production from T4 by protecting rT3 from being degraded and/or diminishing the inhibitory effect of this iodothyronine on its own production. It was concluded that rT3 influenced its own production and that this effect may represent an important autoregulatory process in the iodothyronine metabolism.

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