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Biomedical subjects

C K Kurup

Publications and source records attributed to C K Kurup.

At least 73 records · Page 4Linked to original sources
PubMed1974

Mode of inhibition of mitochondrial energy transduction by chlorophenoxyisobutyrate.

1. alpha-p-Chlorophenoxyisobutyric acid, the ethyl ester of which is widely used as an antihypercholesterolaemic drug, is an inhibitor of energy-transfer reactions in isolated rat liver mitochondria. 2. The compound at lower concentrations (<4.0mumol/mg of mitochondrial protein) inhibits state 3 oxidation, stimulates state 4 oxidation, abolishes respiratory control and stimulates the latent adenosine triphosphatase activity of mitochondria. The inhibition imposed on state 3 oxidation is relieved by dinitrophenol. 3. At higher concentrations it inhibits coupled phosphorylation as well as dinitrophenol-stimulated adenosine triphosphatase activity. The inhibition of state 3 oxidation under these conditions is not reversed by uncouplers. 4. The three coupling sites of phosphorylation exhibit differential susceptibility to inactivation by this compound. Coupled phosphorylation at the first site is abolished at a drug concentration of 3.0mumol/mg of protein. The third site is inactivated when the concentration of the drug reaches 5.0mumol/mg of protein. The second site is the most refractory and drug concentrations of the order of 10.0mumol/mg of protein are required effectively to inhibit phosphorylation at this site. 5. The compound also inhibits ATP-dependent reversal of electron transport as well as the adenosine triphosphatase activity in submitochondrial particles. 6. The oxidation of NADH and succinate in these particles is not inhibited. 7. These properties indicate that the compound acts as an ;inhibitory uncoupler' of energy-transfer reactions in isolated mitochondria.

Adenosine Triphosphatases↗
PubMed1972

Effect of hypobaric stress on enzymes of tryptophan metabolism.

1. On exposure of rats to hypobaric stress the tryptophan pyrrolase and tyrosine aminotransferase activities of the liver increased about threefold in 4h. 2. The tryptophan hydroxylase activity increased about 50% on exposure for 24h or more. 3. The increased activities reverted to the basal value on removal of the stress. 4. Treatment with cycloheximide inhibited the increase in the enzyme activities when the time of exposure was short (4h). However, the inhibitor-treated animals showed paradoxically high tyrosine aminotransferase activity on prolonged exposure (24h). 5. The pattern of haematin saturation indicated that the increase in pyrrolase activity under low pressure resembled that obtained with cortisol and not with tryptophan. 6. Repeated administration of cortisol or tryptophan did not have any effect on the activity of tryptophan hydroxylase. 7. The stress-induced increase in hydroxylase activity was not eliminated by the prior administration of 5-hydroxytryptophan to the animals.

5-Hydroxytryptophan↗
PubMed1972

Increase in hepatic catalase and glycerol phosphate dehydrogenase activities on administration of clofibrate and clofenapate to the rat.

1. Clofenapate (methyl 2-[4-(p-chlorophenyl)phenoxy]-2-methylpropionate) fed to the rat in the diet increased the content of mitochondrial protein in the liver by 50-60%. In this respect it resembled the related compound clofibrate (ethyl alpha-p-chlorophenoxyisobutyrate), which is widely used as an antihypercholesterolaemic drug. 2. Both compounds when fed to the rat enhanced the activity of alpha-glycerol phosphate dehydrogenase in the liver mitochondria manyfold, but were without effect on the enzyme in the soluble fraction. 3. On the other hand, the catalase activity in the supernatant fraction increased twofold after administration of the drugs. The mitochondrial catalase activity showed a consistent decrease. 4. It was unlikely that under the influence of the drug the increase in catalase activity took place in the mitochondrial particles and was leached into the cytosol during isolation. 5. The increase in catalase activity in the cytosol under the influence of the drug is best explained on the assumption that peroxisomes which contain this enzyme, and which are known to increase on administration of the drug, were broken during the process of cellular fractionation and released the enzyme into the cytosol. 6. All the above effects shown by both drugs were fully reversed when drugs were withdrawn from the diet. 7. Clofenapate was effective in bringing about the above changes when administered to the animal at one-hundredth the concentration of clofibrate.

Animals↗
PubMed1970

Increase of hepatic mitochondria on administration of ethyl alpha-p-chlorophenoxyisobutyrate to the rat.

1. The antihypercholesterolaemic drug ethyl alpha-p-chlorophenoxyisobutyrate when fed to the rat orally or mixed with the diet increased the content of mitochondria in the liver by 50-100%. Other subcellular fractions did not show any significant change. 2. In oxidative activity, respiratory control and phosphorylating ability no significant difference was observed between the mitochondria isolated from the livers of the drug-treated rats and those from normal animals. 3. In agreement with earlier reports, administration of the drug depressed the concentration of serum cholesterol and increased liver weight and the liver content of ubiquinone. However, the increase of ubiquinone was greater in the nuclear than in the mitochondrial protein.

Animals↗
PubMed1969

The cryptic nature of hepatic microsomal sulphite oxidase.

1. The activity of rat liver microsomal sulphite oxidase (EC 1.8.3.1) was increased several-fold on aging of microsomes, on delipidation by extraction with acetone or on solubilization with deoxycholate, suggesting its existence in a cryptic state. 2. In rat liver most of the sulphite oxidase was present in the nuclear fraction and only a small portion in the microsomes. 3. Microsomal sulphite oxidase activity was low in the developing embryo and increased rapidly after birth.

Acetone↗