scholarly journals Effect of streptozotocin-diabetes on rat liver mitochondrial adenosine triphosphatase turnover

1988 ◽  
Vol 251 (2) ◽  
pp. 621-624 ◽  
Author(s):  
A Jordá ◽  
E Pérez-Pastor ◽  
M Portolés
Keyword(s):  
Rat Liver ◽  
Half Life ◽  
Adenosine Triphosphatase ◽  
Streptozotocin Diabetes ◽  
Diabetic Rats ◽  
Mitochondrial Enzymes ◽  
Turnover Rates ◽  
Membrane Atpase ◽  
Isotope Technique ◽  
Double Isotope

The apparent turnover rates of some mitochondrial enzymes can be modified in diabetes. We studied the effect of streptozotocin-diabetes on the half-life of a protein tightly bound to the inner membrane, ATPase. The half-life (t 1/2), measured by the double-isotope technique, decreased by approx. 20% in diabetes (from approximately equal to 2.56 days in controls to approximately equal to 2.06 days in diabetic rats). These results suggest that diabetes produces an increase in degradation of ATPase by a mechanism which is not yet clear, possibly influenced by alterations induced by diabetes in hepatic lysosomes that are associated with hepatic autophagy.

scholarly journals Species and tissue distribution of the regulatory protein of glucokinase

1993 ◽  
Vol 294 (2) ◽  
pp. 551-556 ◽  
Author(s):  
A Vandercammen ◽  
E Van Schaftingen
Keyword(s):  
Guinea Pig ◽  
Rat Liver ◽  
Human Liver ◽  
Regulatory Protein ◽  
Control Level ◽  
Streptozotocin Diabetes ◽  
Diabetic Rats ◽  
Rat Tissues ◽  
Adult Rat ◽  
Toad Bufo

Rat liver is known to contain a regulatory protein that inhibits glucokinase (hexokinase IV or D) competitively versus glucose. This inhibition is greatly reinforced by the presence of fructose 6-phosphate and antagonized by fructose 1-phosphate and by KCl. This protein was now measured in various rat tissues and in the livers of various species by the inhibition it exerts on rat liver glucokinase. Rat, mouse, rabbit, guinea-pig and pig liver, all of which contain glucokinase, also contained between 60 and 200 units/g of tissue of a regulatory protein displaying the properties mentioned above. By contrast, this protein could not be detected in cat, goat, chicken or trout liver, or in rat brain, heart, skeletal muscle, kidney and spleen, all tissues from which glucokinase is missing. Fructose 1-phosphate stimulated glucokinase in extracts of human liver, indicating the presence of regulatory protein. In addition, antibodies raised against rat regulatory protein allowed the detection of an approximately 60 kDa polypeptide in rat, guinea pig, rabbit and human liver. The livers of the toad Bufo marinus, of Xenopus laevis and of the turtle Pseudemys scripta elegans contained a regulatory protein similar to that of the rat, with, however, the major difference that it was not sensitive to fructose 6-phosphate or fructose 1-phosphate. In rat liver, the regulatory protein was detectable 4 days before birth. Its concentration increased afterwards to reach the adult level at day 30 of extrauterine life, whereas glucokinase only appeared after day 15. In the liver of the adult rat, starvation and streptozotocin-diabetes caused a 50-60% decrease in the concentration of regulatory protein after 7 days, whereas glucokinase activity fell to about 20% of its initial level. When 4-day-starved rats were refed, or when diabetic rats were treated with insulin, the concentration of regulatory protein slowly increased to reach about 85% of the control level after 3 days, whereas the glucokinase activity was normalized after the same delay. The fact that there appears to be no situation in which glucokinase is expressed without regulatory protein is in agreement with the notion that the regulatory protein forms a functional entity with this enzyme.

scholarly journals Studies on the metabolism of rat liver copper-metallothionein

1985 ◽  
Vol 227 (3) ◽  
pp. 903-908 ◽  
Author(s):  
R K Mehra ◽  
I Bremner
Keyword(s):  
Rat Liver ◽  
Half Life ◽  
Pulse Labelling ◽  
Turnover Rates ◽  
Liver Cytosol ◽  
Total Liver ◽  
Liver Copper

The degradation of purified 35S-labelled rat liver isometallothioneins (MT) by lysosomal extracts was studied. Zn-MT-I was more readily hydrolysed than Zn-MT-II, but no significant degradation of the Cu-containing metallothioneins could be detected, even after 24 h incubation. The susceptibility of MT to degradation in vitro may be related to the strength of the metal-thiolate bonds. However, the turnover rates of cytosolic MT in vivo, as established by pulse-labelling techniques, are apparently subject to different controls. The half-lives of MT-I and -II in the liver cytosol of Cu2+-injected rats were only 15.4 +/- 1.5 and 18.2 +/- 1.1 h respectively. Approx. 25% of the total liver MT was present in particulate fractions (probably in lysosomes) of the liver and had a half-life of 25.1 +/- 4.1 h.

A Double Isotope Technique for Estimating Insulin Degradation in Vivo

1974 ◽  
Vol 13 (01) ◽  
pp. 85-97
Author(s):  
F. Ritzl ◽  
L. E. Feinendegen ◽  
H. G. Schnippering
Keyword(s):  
Diabetes Mellitus ◽  
Half Life ◽  
Isotopic Ratio ◽  
Internal Standard ◽  
The Body ◽  
Autoimmune Response ◽  
Clinical Diabetes ◽  
Insulin Degradation ◽  
Isotope Technique ◽  
Double Isotope

Summary1) A double isotope technique is described which permits measuring by external counting the catabolism of insulin in the human liver. 131I-insulin is used together with 51Cr-insulin as internal standard. Following catabolism of the labeled insulins 131I migrates into the iodine pool of the body whereas 51Cr remains at the site of insulin breakdown. Therefore, site and rate of insulin catabolism can be recognized from the change in the isotopic ratio 131I/51Cr.2) In the livers of 3 normal individuals, insulin half-lives of 58, 95, and 92.5 minutes were measured. In 3 patients with sub-clinical diabetes mellitus, insulin half-lives were 124.5 minutes, 127 minutes, and 99.5 minutes. One patient with clinical diabetes showed an insulin half-life of only 47.8 minutes; a second patient with clinical diabetes mellitus due to autoimmune response leading to large amounts of insulin antibody in his peripheral blood, showed an insulin half-life greatly prolonged to 972 minutes.3) The 51Cr-labeled insulin was indistinguishable from 125I-labeled insulin in the immunoassay, in molecular size, in diffusion rate in tissues, absorption to subcellular particles, and rate of hydrolysis in liver homogenates in vitro.

Turnover and Distribution of 131Iodine-Labelled Human Fibrinogen

1964 ◽  
Vol 11 (02) ◽  
pp. 404-422 ◽  
Author(s):  
Annemarie Amris ◽  
C. J Amris
Keyword(s):  
Body Weight ◽  
Cancer Patient ◽  
Distribution Ratio ◽  
Half Life ◽  
Fibrinolytic Activity ◽  
The Other ◽  
Turnover Rates ◽  
Human Fibrinogen ◽  
Coagulation Defects ◽  
Fractional Turnover

Summary14 patients (5 diabetics with arteriosclerotic complications, 4 patients with thrombo-embolic disease, 4 with cirrhosis, coagulation defects and increased fibrinolytic activity, and 1 cancer patient) and 3 control patients were subjected to turnover studies with 13iodine labelled human fibrinogen.Half-life times in the control patients were found to be 4 days, the fractional turnover rates 19–23 per cent, of intravascular fibrinogen per day, and the absolute turnover 0.02 to 0.06 gm per day per kg. body weight. The other patient’s half-life times and turnover rates varied considerably from 0.9–5.5 days, 13–160 per cent, per day of intravascular fibrinogen and 0.02–0.4 gm per day per kg. body weight respectively.As fibrinogen unlike other proteins subjected to turnover studies, is converted to fibrin, it is not possible to measure the true intra-extravascular distribution ratio of fibrinogen. But intravascular fibrinogen could be approximated to constitute 68–99 per cent, of the total fibrinogen. There is justification in believing that fibrinogen is degradated through a continuous coagulation in equilibrium with fibrinolysis, and that the organism contains a greater mass of fibrin, the “fibrin pool”. Considerations of the turnover mechanism can however only be hypothetical.

STUDIES ON THYROIDAL COLLOID PINOCYTOSIS USING A DOUBLE ISOTOPE TECHNIQUE

1972 ◽  
Vol 70 (1) ◽  
pp. 48-55 ◽  
Author(s):  
Mario A. Pisarev ◽  
Noe Altschuler ◽  
Leslie J. DeGroot
Keyword(s):  
Acid Phosphatase ◽  
Thyroid Hormone ◽  
Trichloroacetic Acid ◽  
Specific Activity ◽  
Acid Precipitation ◽  
Solvent System ◽  
Blood Stream ◽  
Radioactive Materials ◽  
Isotope Technique ◽  
Double Isotope

ABSTRACT The process of secretion of the thyroid hormone involves several steps: pinocytosis of thyroglobulin, fusion of the colloid droplets with the lysosomes, digestion of thyroglobulin by a cathepsin, dehalogenation of tyrosines and release of thyronines into the blood stream. The present paper describes a double isotope technique for studying the first two steps. Thyrotrophin (TSH) administration to rats increased the radioactivity present in all fractions, specially in the 15 000 × g pellet. When the subcellular distribution of acid phosphatase was determined, the highest specific activity was found in this fraction, thus indicating the presence of lysosomes. The content of radioactive materials in the 15 000 × g pellet was analyzed by trichloroacetic acid precipitation and by ascending paper chromatography using n-butanol:ethanol:ammonium hydroxide (5:1:2;v/v) as solvent system. The results obtained showed that 90% of the radioactivity was protein bound and strongly suggest that this material is thyroglobulin.

scholarly journals Anomeric specificity of d-glucose phosphorylation by rat liver glucose-6-phosphatase

1989 ◽  
Vol 261 (2) ◽  
pp. 509-513
Author(s):  
R Ramirez ◽  
D Zähner ◽  
G Marynissen ◽  
A Sener ◽  
W J Malaisse
Keyword(s):  
Rat Liver ◽  
Glycogen Synthesis ◽  
Liver Microsomes ◽  
Diabetic Rats ◽  
Enzymic Activity ◽  
Rat Liver Microsomes ◽  
Maximal Velocity ◽  
Carbamoyl Phosphate ◽  
Glucose Phosphorylation ◽  
Anomeric Specificity

The anomeric specificity of D-glucose phosphorylation by hepatic glucose-6-phosphatase was examined in rat liver microsomes incubated in the presence of carbamoyl phosphate. At 10 degrees C, the Km for the equilibrated hexose and phosphate donor was close to 56 mM and 11 mM, respectively. The enzymic activity, which was increased in diabetic rats, was about 40% lower in untreated than in sonicated microsomes. No anomeric difference in affinity was found in sonicated microsomes. In untreated microsomes, however, the Km for beta-D-glucose was slightly lower than that for alpha-D-glucose. The maximal velocity was higher with beta- than alpha-D-glucose in both untreated and sonicated microsomes. These data indicate that the phosphotransferase activity of glucose-6-phosphatase cannot account for the higher rate of glycolysis and glycogen synthesis found in hepatocytes exposed to alpha- rather than beta-D-glucose.

scholarly journals The effects of environmental temperature on the properties of myofibrillar adenosine triphosphatase from various species of fish

1973 ◽  
Vol 133 (4) ◽  
pp. 735-738 ◽  
Author(s):  
Ian A. Johnston ◽  
Neil Frearson ◽  
Geoffrey Goldspink
Keyword(s):  
Low Temperatures ◽  
Half Life ◽  
Adenosine Triphosphatase ◽  
Environmental Temperature ◽  
Cold Water ◽  
Warm Water ◽  
Adenosine Triphosphatase Activity ◽  
Water Fish ◽  
Different Temperatures ◽  
Myotomal Muscle

1. Myofibrillar adenosine triphosphatase (ATPase) activities were measured for white myotomal muscle of 19 species of fish. 2. The activity was measured at different temperatures and after periods of preincubation at 37°C. 3. The inactivation half-life at 37°C depended on environmental temperature, increasing as the temperature increased. 4. Cold-water fish had higher myofibrillar adenosine triphosphatase activity at low temperatures than had warm-water fish. 5. The significance of these results is discussed.

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