Uptake, metabolism and subcellular distribution of [125I]T4 in calf thyroid slices

1984 ◽  
Vol 105 (3) ◽  
pp. 341-349 ◽  
Author(s):  
G. D. Chazenbalk ◽  
D. L. Kleiman de Pisarev ◽  
G. J. Juvenal ◽  
M. A. Pisarev
Keyword(s):  
Rat Liver ◽  
Paper Chromatography ◽  
Subcellular Distribution ◽  
Inhibitory Action ◽  
Soluble Fraction ◽  
Temperature Dependent ◽  
Liver Slices ◽  
Liver Homogenates

Abstract. Previous work from our laboratory has shown that iodothyronines have a direct inhibitory action on the thyroid. In the present studies the uptake, metabolism and subcellular distribution of labelled thyroxine were analyzed. The entry of this hormone reaches a plateau after 15–20 min incubation and is temperature-dependent. The T/M values for T4 were much lower than those of labelled T3 and the curve was different from that obtained with [125I]. The influence of a series of compounds on the T/M values for thyroxine was studied. KI, T3, IOP PTU and MMI were without effect. Absence of Ca++ in the buffer, or addition of KClO4 or ouabain caused a slight decrease, while TSH produced a stimulation in the T/M ratio. Calf thyroid slices dehalogenated thyroxine, producing both T3 and rT3. TSH increased the generation of these two compounds. Neither PTU nor IOP altered the production of T3 and rT3 significantly. The lack of effect of IOP on T3 and rT3 generation was confirmed in calf thyroid homogenates. However, and in agreement with previous reports, IOP significantly decreased production of both triiodothyronines in rat liver slices and in rat liver homogenates. When the subcellular distribution of labelled thyroxine was examined most of the radioactivity appeared in the soluble fraction and less than 1 % was present in purified nuclei. The addition of unlabelled thyroxine to the slices only caused a significant displacement in the radioactivity of purified nuclei. The presence of labelled thyroxine in the nuclei was confirmed by paper chromatography.

scholarly journals The influence of some methodological factors on measurement of tryptophan oxygenase activities in crude homogenates of rat liver

1983 ◽  
Vol 209 (3) ◽  
pp. 831-836 ◽  
Author(s):  
L Stowell ◽  
J Mørland
Keyword(s):  
Rat Liver ◽  
Liver Tissue ◽  
Post Mortem ◽  
Temperature Dependent ◽  
Tryptophan Oxygenase ◽  
Oxygenase Activity ◽  
Liver Homogenates ◽  
Independent Reaction

1. With two different methods for assaying the tryptophan oxygenase activity in rat liver homogenates, the effects of some methodological factors on the activity of the enzyme were studied. 2. In fed, but not in starved, rats a compound(s) absorbing at 365 nm, interfering with the reading of kynurenine absorbance, disappeared gradually during incubation. 3. A correction for this tryptophan-independent reaction was necessary in order to determine correct tryptophan oxygenase activity. 4. Blood remaining in liver tissue post mortem can serve as a source of cofactor haem for tryptophan oxygenase, causing spuriously high values for the activity of the holoenzyme form of tryptophan oxygenase. 5. A rapid and progressive activation of tryptophan oxygenase post mortem occurs in undisrupted liver tissue, and this activation is temperature-dependent.

INTRACELLULAR DISTRIBUTION OF PHOSPHOMONOESTERASES IN RAT LIVER HOMOGENATE

1954 ◽  
Vol 32 (1) ◽  
pp. 383-394 ◽  
Author(s):  
Claude Allard ◽  
Gaston de Lamirande ◽  
Hugo Faria ◽  
Antonio Cantero
Keyword(s):  
Acid Phosphatase ◽  
Rat Liver ◽  
Mouse Liver ◽  
Soluble Fraction ◽  
Liver Homogenate ◽  
Mitochondrial Fraction ◽  
Nuclear Fraction ◽  
Absolute Requirement ◽  
Rat Liver Cells ◽  
Liver Homogenates

Acid phosphatase or phosphomonoesterase II activity of rat and mouse liver homogenates, prepared in 0.25 M sucrose, was found mainly in the cytoplasmic granules. Since the small percentage of activity of the nuclear fraction activity could be explained by the presence of mitochondria (which were actually counted in this fraction) it is concluded that rat and mouse liver nuclei do not contain acid phosphatase activity.A rather broad range of acid phosphatase activity was observed in rat and mouse livers depending on the time elapsed between the preparation of homogenate and the activity determinations. However, a preincubation of the tissues or isolated fractions at 37° C. for 60 min. was sufficient to increase the activity to an optimal value, and thus eliminate variations due to the latency of this enzyme.Alkaline phosphatase or phosphomonoesterase I activity was also found to be latent in rat liver homogenates. The phenomenon was less apparent than for acid phosphatase and seemed to depend mostly on the nature of the buffer employed in the assay system.Some evidence for the presence of two forms of alkaline phosphatase in rat liver cells is presented. One form of the enzyme was found to have an absolute requirement of magnesium for activity and was present in the soluble fraction, whereas the other which was not activated by magnesium seemed firmly linked to the nuclei and microsomes and was absent in the soluble fraction. The activity in the mitochondrial fraction was small and seemed of doubtful significance.

INTRACELLULAR DISTRIBUTION OF PHOSPHOMONOESTERASES IN RAT LIVER HOMOGENATE

1954 ◽  
Vol 32 (4) ◽  
pp. 383-394 ◽  
Author(s):  
Claude Allard ◽  
Gaston de Lamirande ◽  
Hugo Faria ◽  
Antonio Cantero
Keyword(s):  
Acid Phosphatase ◽  
Rat Liver ◽  
Mouse Liver ◽  
Soluble Fraction ◽  
Liver Homogenate ◽  
Mitochondrial Fraction ◽  
Nuclear Fraction ◽  
Absolute Requirement ◽  
Rat Liver Cells ◽  
Liver Homogenates

Acid phosphatase or phosphomonoesterase II activity of rat and mouse liver homogenates, prepared in 0.25 M sucrose, was found mainly in the cytoplasmic granules. Since the small percentage of activity of the nuclear fraction activity could be explained by the presence of mitochondria (which were actually counted in this fraction) it is concluded that rat and mouse liver nuclei do not contain acid phosphatase activity.A rather broad range of acid phosphatase activity was observed in rat and mouse livers depending on the time elapsed between the preparation of homogenate and the activity determinations. However, a preincubation of the tissues or isolated fractions at 37° C. for 60 min. was sufficient to increase the activity to an optimal value, and thus eliminate variations due to the latency of this enzyme.Alkaline phosphatase or phosphomonoesterase I activity was also found to be latent in rat liver homogenates. The phenomenon was less apparent than for acid phosphatase and seemed to depend mostly on the nature of the buffer employed in the assay system.Some evidence for the presence of two forms of alkaline phosphatase in rat liver cells is presented. One form of the enzyme was found to have an absolute requirement of magnesium for activity and was present in the soluble fraction, whereas the other which was not activated by magnesium seemed firmly linked to the nuclei and microsomes and was absent in the soluble fraction. The activity in the mitochondrial fraction was small and seemed of doubtful significance.

PHOSPHOLIPID METABOLISM IN RAT LIVER SLICES: EFFECT OF HYPOPHYSECTOMY AND ADRENALECTOMY ON THE LABELLING OF PHOSPHOLIPIDS WITH ACETATE-1-C14

1957 ◽  
Vol 35 (2) ◽  
pp. 143-150 ◽  
Author(s):  
Dorothy Kline ◽  
R. J. Rossiter
Keyword(s):  
Fatty Acids ◽  
Nutritional Status ◽  
Rat Liver ◽  
Adrenal Glands ◽  
Soluble Fraction ◽  
Phospholipid Metabolism ◽  
Acetone Insoluble ◽  
Liver Slices ◽  
Ad Libitum

In rats fed ad libitum the labelling of the acetone-insoluble lipids (phospholipids) of liver slices respiring in the presence of acetate-1-C14 was decreased 2 days after the removal of either the pituitary or the adrenal glands. The effect was not observed 4 days after hypophysectomy. Moreover, the effect was not observed with liver slices from hypophysectomized or adrenalectomized animals that were either deprived of food for the 12 hours immediately prior to killing, or force-fed with glucose 4 hours before killing. Hypophysectomy caused a decrease in the labelling of the fatty acids in the acetone-soluble fraction remaining in solution after precipitation of the phospholipids. This decrease was observed both in liver slices from animals fed ad libitum and in those from fasted (12 hours) animals. In rats fed ad libitum the labelling of the non-esterified cholesterol of the liver slices was decreased by hypophysectomy, but not by adrenalectomy. It is concluded that the decrease in the labelling of the acetone-insoluble lipids in liver slices from operated rats was primarily the result of a change in the nutritional status of the operated animals. The data are insufficient to permit any conclusions concerning the cause of the decrease in labelling of either the fatty acids of the acetone-soluble lipids, or the non-esterified cholesterol.

IN VITRO STUDIES ON THE BIOSYNTHESIS OF UBIQUINONE

1960 ◽  
Vol 38 (10) ◽  
pp. 1105-1115 ◽  
Author(s):  
W. E. J. Phillips
Keyword(s):  
Rat Liver ◽  
Intestinal Mucosa ◽  
Mevalonic Acid ◽  
In Vitro Studies ◽  
Detectable Amount ◽  
Exogenous Factor ◽  
Liver Slices ◽  
Liver Homogenates ◽  
Isolated Tissues

Radioactive ubiquinone can be isolated from rat liver following intraperitoneal injections of C14-acetate or mevalonic acid. No detectable amount of radioactive ubiquinone could be isolated from liver homogenates, liver slices, or intestinal mucosa incubated in vitro with C14-acetate or mevalonic acid. The possible requirement of isolated tissues for an exogenous factor is discussed.

THE EFFECT OF FASTING ON ESTERIFICATION OF PALMITATE BY RAT LIVER IN VITRO

1966 ◽  
Vol 44 (1) ◽  
pp. 129-140 ◽  
Author(s):  
Bernard Rubenstein ◽  
David Rubinstein
Keyword(s):  
Rat Liver ◽  
Incubation Medium ◽  
Intact Cell ◽  
Glycerol Kinase ◽  
Glycerophosphate Dehydrogenase ◽  
Liver Slices ◽  
Liver Homogenates

The ability of liver slices from rats fasted 48 hours to esterify palmitate-1-14C is about half of that of slices from fed animals. The same effect can be observed in homogenates of liver freed of nuclei, either with or without mitochondria. In both preparations, the synthesis of triglycerides is chiefly affected. The decrease in esterification by homogenate supernatants containing microsomes from fasted animals can be overcome by using increased amounts of ATP or an ATP generator and NaF in the incubation medium. The ATPase responsible for the higher ATP requirement in liver homogenates from fasted animals is Mg++-dependent. Higher concentrations of ATP inhibit esterification by mitochondrial preparations. Incorporation of both palmitate-9-10-3H and of glycerol-1-3-14C is reduced to the same extent for each compound in slices from fasting animals. Glycerol kinase and α-glycerophosphate dehydrogenase are both unaffected by 48 hours' fasting. It is concluded that the decrease in ATP from the activation of ATPase is responsible for the decreased esterification in the intact cell.

scholarly journals Substrate Specificity of Mammalian D-Glucuronolactone Dehydrogenase

1973 ◽  
Vol 26 (4) ◽  
pp. 839 ◽  
Author(s):  
PG Tonkes ◽  
CA Marsh
Keyword(s):  
Substrate Specificity ◽  
Rat Liver ◽  
Soluble Fraction ◽  
Male Rat ◽  
Liver Homogenates

The NAD+-dependent D-glucuronolactone dehydrogenase from the soluble fraction of male rat liver homogenates was purified 350-fold with an overall recovery of 11 %.

Intensification of the xanthine oxidase activity of rat liver homogenates on storage

1968 ◽  
Vol 46 (9) ◽  
pp. 1047-1056
Author(s):  
D. G. R. Blair ◽  
B. D. McLennan
Keyword(s):  
Xanthine Oxidase ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Enzyme Assay ◽  
Substrate Inhibition ◽  
Temperature Dependent ◽  
Xanthine Oxidase Activity ◽  
Aging Period ◽  
Liver Homogenates ◽  
High Concentrations

The xanthine oxidase activity of rat liver homogenates increased severalfold when the homogenates were stored (aged) at 4 °C for several days. The increase could be demonstrated by measuring xanthine oxidase activity by xanthine utilization or allantoin formation from xanthine. The increase in activity was not correlated with the concentrations of allantoin, uric acid, xanthine, or hypoxanthine in the homogenates, and, therefore, is not attributed to decrease of substrate inhibition, but its demonstration was partially inhibited by relatively high concentrations of xanthine in the enzyme-assay reaction medium.The increase in xanthine oxidase activity was temperature-dependent and was unaffected by the presence of glucose or adenosine 5′-triphosphate. Lysis of unbroken cells during the aging period and microbial contamination were not contributory. Dialysis of a fresh homogenate partially inhibited the increase in activity, but the addition of the dialysate of an aging homogenate to a dialyzed or fresh homogenate did not stimulate activity.The mechanism of the increase in xanthine oxidase activity has not been elucidated, but the fact that stimulation of the activity by methylene blue decreases as the homogenates age, suggests that the rate at which reduced xanthine oxidase is oxidized by air may increase with homogenate aging.

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