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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Carnitine acetyltransferase (EC 2.3.1.7) activity in sheep liver mitochondria was 76nmol/min per mg of protein, in contrast with 1.7 for rat liver mitochondria. The activity in bovine liver mitochondria was comparable with that of sheep liver mitochondria. Carnitine palmitoyltransferase activity was the same in both sheep and rat liver mitochondria. 2. The [free carnitine]/[acetylcarnitine] ratio in sheep liver ranged from 6:1 for animals fed ad libitum on lucerne to approx. 1:1 for animals grazed on open pastures. This change in ratio appeared to reflect the ratio of propionic acid to acetic acid produced in the rumen of the sheep under the two dietary conditions. 3. In sheep starved for 7 days the [free carnitine]/[acetylcarnitine] ratio in the liver was 0.46:1. The increase in acetylcarnitine on starvation was not at the expense of free carnitine, as the amounts of free carnitine and total acid-soluble carnitine rose approximately fivefold on starvation. An even more dramatic increase in total acid-soluble carnitine of the liver was seen in an alloxan-diabetic sheep. 4. The [free CoA]/[acetyl-CoA] ratio in the liver ranged from 1:1 in the sheep fed on lucerne to 0.34:1 for animals starved for 7 days. 5. The importance of carnitine acetyltransferase in sheep liver and its role in relieving ;acetyl pressure' on the CoA system is discussed.
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PMID:Aspects of carnitine ester metabolism in sheep liver. 548 54

1. The content of citrate in ;freeze-clamped' livers from starved and alloxan-diabetic rats was measured by using the specific citrate assay method of Gruber & Moellering (1966). 2. The content of citrate fell progressively during a period of 48hr. starvation to reach a plateau value that is 50% of the value for livers from fed rats. Some possible explanations for the conflicting reports of changes in hepatic citrate content during starvation are discussed. 3. The hepatic contents of ATP, pyruvate, lactate, glycogen and the hexose phosphates were decreased during starvation, whereas those of acetyl-CoA and AMP were increased. 4. Acute alloxan-diabetes produced similar changes in the contents of these metabolic intermediates. 5. The effects of starvation and diabetes on the citrate and acetyl-CoA contents are discussed in relation to control of gluconeogenesis, fatty acid synthesis and the activity of citrate synthase.
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PMID:The effects of starvation and alloxan-diabetes on the contents of citrate and other metabolic intermediates in rat liver. 565 Mar 65

1. The activities of hydroxymethylglutaryl-CoA synthase and lyase in rat liver were found to be two- to 15-fold greater than those reported by other authors under similar conditions. 2. When expressed on the basis of body weight, no appreciable differences were found between the activities of hydroxymethylglutaryl-CoA synthase in whole homogenates of livers from normal and starved rats. The synthase activity increased by 70% and 140% in livers of alloxan-diabetic rats and rats fed on a high-fat diet respectively. 3. Hydroxymethylglutaryl-CoA lyase activity showed no significant increases in starvation or alloxan-diabetes, but a 40% increase was found in fat-fed rats. 4. Less than 12% of the activities of both enzymes were found in the cytoplasmic fraction of normal liver. The cytoplasmic activity doubled in alloxan-diabetes and starvation; on feeding with a high-fat diet the increase, though significant, was less marked. 6. The intracellular distribution of glutamate dehydrogenase indicated that the changes in the cytoplasmic activities observed were not due to leakage from the mitochondria. 7. Feeding with a normal or high-fat diet after 48hr. starvation caused within 24hr. a decrease in the cytoplasmic activity of hydroxymethylglutaryl-CoA synthase to values lower than those found in rats fed on a corresponding diet for a longer period of time. 8. Acetoacetyl-CoA deacylase activity in liver was about 20% of that of hydroxymethylglutaryl-CoA synthase and was primarily located in the cytoplasm. Starvation or alloxan-diabetes did not alter the acetoacetyl-CoA deacylase activity. 9. It is concluded that variations in the concentrations of enzymes involved in acetoacetate synthesis play no major role in the regulation of ketone-body formation in starvation and alloxan-diabetes. The changes in the cytoplasmic activities of hydroxymethylglutaryl-CoA synthase and lyase suggest that acetoacetate synthesis can occur in the cytoplasm. This may play a role in the disposal of surplus acetyl-CoA arising in the cytoplasm when lipogenesis is inhibited.
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PMID:Activity and intracellular distribution of enzymes of ketone-body metabolism in rat liver. 566 51

1. Rates of appearance and disappearance of total ketone bodies were determined in normal, starved and alloxan-diabetic rats by measuring specific radioactivities and concentrations of blood acetoacetate and 3-hydroxybutyrate at different times after injection of 3-hydroxy[(14)C]butyrate. 2. The mean rates of appearance were 1.7, 4.2 and 10.9mumoles/min./100g. body wt. respectively for normal, starved and alloxan-diabetic rats. The rates of disappearance were of the same order of magnitude as the rates of appearance. 3. There was a direct correlation between the rates of appearance and disappearance and the blood concentrations of the ketone bodies. 4. The results indicate that in the rat increased ketone-body production is paralleled by increased ketone-body utilization and that the raised ketone-body concentration in the blood in starvation and alloxan-diabetes is due to a slight imbalance between the rates of production and utilization. 5. The findings are discussed in relation to the concept that ketone bodies can serve as fuels of respiration when the supply of carbohydrate is limited.
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PMID:Turnover rates of ketone bodies in normal, starved and alloxan-diabetic rats. 570 13

1. Measurements were made of the non-oxidative reactions of the pentose phosphate cycle in liver (transketolase, transaldolase, ribulose 5-phosphate epimerase and ribose 5-phosphate isomerase activities) in a variety of hormonal and nutritional conditions. In addition, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were measured for comparison with the oxidative reactions of the cycle; hexokinase, glucokinase and phosphoglucose isomerase activities were also included. Starvation for 2 days caused significant lowering of activity of all the enzymes of the pentose phosphate cycle based on activity in the whole liver. Re-feeding with a high-carbohydrate diet restored all the enzyme activities to the range of the control values with the exception of that of glucose 6-phosphate dehydrogenase, which showed the well-known ;overshoot' effect. Re-feeding with a high-fat diet also restored the activities of all the enzymes of the pentose phosphate cycle and of hexokinase; glucokinase activity alone remained unchanged. Expressed as units/g. of liver or units/mg. of protein hexokinase, glucose 6-phosphate dehydrogenase, transketolase and pentose phosphate isomerase activities were unchanged by starvation; both 6-phosphogluconate dehydrogenase and ribulose 5-phosphate epimerase activities decreased faster than the liver weight or protein content. 2. Alloxan-diabetes resulted in a decrease of approx. 30-40% in the activities of 6-phosphogluconate dehydrogenase, ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase and transketolase; in contrast with this glucose 6-phosphate dehydrogenase, transaldolase and phosphoglucose isomerase activities were unchanged. Treatment of alloxan-diabetic rats with protamine-zinc-insulin for 3 days caused a very marked increase to above normal levels of activity in all the enzymes of the pentose phosphate pathway except ribulose 5-phosphate epimerase, which was restored to the control value. Hexokinase activity was also raised by this treatment. After 7 days treatment of alloxan-diabetic rats with protamine-zinc-insulin the enzyme activities returned towards the control values. 3. In adrenalectomized rats the two most important changes were the rise in hexokinase activity and the fall in transketolase activity; in addition, ribulose 5-phosphate epimerase activity was also decreased. These effects were reversed by cortisone treatment. In addition, in cortisone-treated adrenalectomized rats glucokinase activity was significantly lower than the control value. 4. In thyroidectomized rats both ribose 5-phosphate isomerase and transketolase activities were decreased; in contrast with this transaldolase activity did not change significantly. Hypophysectomy caused a 50% fall in transketolase activity that was partially reversed by treatment with thyroxine and almost fully reversed by treatment with growth hormone for 8 days. 5. The results are discussed in relation to the hormonal control of the non-oxidative reactions of the pentose phosphate cycle, the marked changes in transketolase activity being particularly outstanding.
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PMID:The pentose phosphate pathway of glucose metabolism. Hormonal and dietary control of the oxidative and non-oxidative reactions of the cycle in liver. 579 34

1. Measurements were made of the activities of the enzymes of the pentose phosphate pathway concerned in both the oxidative (glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase) and the non-oxidative (ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase, transketolase and transaldolase) reactions of this pathway, together with hexokinase and phosphoglucose isomerase, in adipose tissue in a variety of nutritional and hormonal conditions. 2. Starvation for 2 days caused a significant decrease in the activities of all the enzymes of the pentose phosphate pathway, with the exception of glucose 6-phosphate dehydrogenase, when expressed as activity/2 fat-pads; only the activities of ribose 5-phosphate isomerase and ribulose 5-phosphate epimerase were significantly decreased on the basis of activity/mg. of protein. Re-feeding with a high-carbohydrate or high-fat diet for 3 days restored the activity of all the enzymes of the pentose phosphate pathway to the range of the control values, with the exception of transketolase, which showed a marked ;overshoot' in rats re-fed with carbohydrate. Starvation for 3 days caused a marked decrease in the activities of glucose 6-phosphate dehydrogenase and transketolase. 3. On the basis of activity/two fat-pads, alloxan-diabetes caused a marked decrease, to about half the control value, in the activities of all the enzymes concerned in the pentose phosphate pathway, transketolase showing the smallest decrease; hexokinase and phosphoglucose isomerase activities were also decreased. Treatment with insulin for 3 and 7 days raised the activities to normal or supranormal values, transketolase showing the most marked ;overshoot' effect. On the basis of activity/mg. of protein the activity of none of the enzymes was significantly decreased in alloxan-diabetes; transketolase and transaldolase activities were raised above the control values. With insulin treatment for 3 or 7 days the activities of all the enzymes were significantly increased, except that of ribulose 5-phosphate epimerase at the shorter time-interval. Glucagon treatment did not alter any of the enzyme activities expressed on either basis. 4. Thyroidectomy caused a decrease of 30-40% in the activities of enzymes of the pentose phosphate pathway, except for transketolase activity, which fell to 50% of the control value. Little change occurred in adipose-tissue weight or protein content. 5. Adrenalectomy caused a decrease of 40% in the activity of glucose 6-phosphate dehydrogenase and of 20-30% in the activities of the remaining enzymes of the pentose phosphate pathway; hexokinase activity was also decreased. Treatment with cortisone for 3 days did not significantly raise the activity from that found in adrenalectomized rats. Treatment of normal rats with high doses of cortisone had no significant effect on the activities of the enzymes of the pentose phosphate pathway in adipose tissue. 6. The changes in enzyme activities are discussed in relation to: (a) the concept of constant-proportion groups of enzymes; (b) the known changes in the flux of glucose through alternative metabolic pathways; (c) the pattern of change found in liver with similar hormonal and dietary conditions.
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PMID:The pentose phosphate pathway of glucose metabolism. Hormonal and dietary control of the oxidative nd non-oxidative reactions and related enzymes of the cycle in adipose tissue. 581 81

1. Glucokinase and hexokinase activities have been determined in the livers of newborn rats and attempts made to influence in vivo the development of the glucokinase. 2. Glucokinase first appears in rat liver about 16 days after birth and adult activities are reached 10-12 days later. Evidence is presented which indicates that this represents synthesis of new protein. Hexokinase activities remain constant throughout the period of glucokinase development. 3. Both exogenous glucose and insulin are necessary for the natural development of glucokinase, for this is retarded in starved and alloxan-diabetic neonatal rats. 4. The absence of glucokinase during the first 2 weeks of extrauterine life in the rat is not due to lack of insulin. 5. Attempts to advance the time at which glucokinase first appears by infusions of glucose, insulin and chlorpropamide alone and in various combinations have resulted in marginal effects only. 6. When rats are starved for 3 days during the period of glucokinase development and then re-fed, glucokinase is more rapidly synthesized, indicating that the potential ability to synthesize glucokinase continues to develop throughout the period of starvation. 7. Some possible reasons for the comparatively late development of glucokinase are discussed.
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PMID:The development of hepatic glucokinase in the neonatal rat. 588 29

The citrate content of rat liver changes little when normal rats are starved, when starved rats are re-fed with various diets and when normal animals are made diabetic with alloxan. The citrate content of rat kidney changes little on starvation, but it doubles on induction of diabetes. Fluoroacetate poisoning has relatively little effect on the citrate content of liver under a variety of conditions except that normal female rats show a 2.4-fold increase. Fluoroacetate poisoning leads to increases in the citrate content of kidney under all conditions. The relevance of these observations to the regulation of fatty acid synthesis is discussed. The acetic anhydride-pyridine method and the pentabromoacetone method for the estimation of citrate are compared.
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PMID:Citrate content of liver and kidney of rat in various metabolic states and in fluoroacetate poisoning. 603 77

1. Methods are described for the extraction of lipid and assay of mono-, di- and tri-glyceride glycerol and phospholipid phosphorus in rat heart and gastrocnemius muscles. 2. In hearts from normal animals, concentrations found were: monoglyceride, 0.6; diglyceride, 0.1; triglyceride, 12.6mumoles of glyceride glycerol/g. of dry muscle; phospholipid, 171mug.atoms of phospholipid phosphorus/g. of dry muscle. Concentrations of glycerides in gastrocnemius muscle were similar to heart muscle but those of phospholipids were lower (64mug.atoms of phospholipid phosphorus/g. of dry muscle). 3. Alloxan-diabetes increased the concentration of triglyceride in the muscles twofold. This increase was shown to be dependent in the heart on the availability of growth hormone and cortisol but not on the availability of dietary lipid. Total glyceride in the heart was increased after 48 and 72hr. starvation but not after 96hr. Changes in glyceride concentration seen in starvation and diabetes were not associated with significant changes in phospholipid concentration. It is suggested that mobilization of free fatty acids in diabetes leads to the synthesis of additional glyceride in muscle. 4. The possible contribution of glyceride fatty acid in the heart to respiration during perfusion has been calculated from the net loss of glyceride during perfusion, and also from the relative rates of lipolysis and esterification and compared with oxidation of fatty acid required for the balance of oxygen consumption (oxygen not utilized in the oxidation of glucose or glycogen glucose). In the normal or diabetic heart perfused with glucose and insulin the breakdown of glyceride can account for the balance of oxygen consumption. In the normal heart perfused without substrate the balance of oxygen consumption is not entirely accounted for by the breakdown of glyceride.
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PMID:Concentrations of glycerides and phospholipids in rat heart and gastrocnemius muscles. Effects of alloxan-diabetes and perfusion. 604 83

It has been previously demonstrated that glucagon increased plasma post-heparin lipolytic activity (PHLA) in normal rats, but this was not the case in alloxan diabetic rats. The present work was designed to determine if the administration of exogenous glucagon (0.2 mg i.v.) during suppression of endogenous hormone secretion with somatostatin modifies the plasma post-heparin lipolytic activity in normal rats and the action of such hormone upon monoglyceride hydrolase (MGH) activity. It was found that exogenous glucagon significatively increased PHLA and MGH activity in normal rats after 18-24 hours of starvation. However, both enzymatic activities were not influenced by exogenous glucagon when they were measured during somatostatin administration. Therefore it is believed that the enhancement of these activities observed when somatostatin was not simultaneously given was due to the insulin secretion that follows the glucagon injection.
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PMID:Glucagon action upon plasma post-heparin lipolytic and monoglyceride hydrolase activities. Studies involving administration of exogenous hormone during suppression of endogenous hormone secretion with somatostatin. 611 26


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