Modification of ornithine decarboxylase activity by adrenergic stimulation in cultured chicken spleen cells

1. In vivo, adrenergic agonists promote an increase of ornithine decarboxylase activity (ODC) in chicken spleen, as opposed to a decrease in thymus and bursa of Fabricius. The increase is not due to the cell fraction separated on Lymphoprep, i.e. the spleen cells, but it could be due to the macrophages. 2. With spleen cells in culture, a marked increase of ODC activity is observed during the first 3 hr, followed by a decrease. 3. cAMP drastically decreases after 10 min in culture. 4. Adrenergic agonists promote a decrease of activity, both alpha and beta receptors being involved in these modifications. TPA promotes partial desensitization. 5. Selenite, which in vivo has the same effect as epinephrine, enhances ODC activity in culture. Propranolol partially counteracts this effect, while prazosin has a synergistic effect. TPA partially desensitizes spleen cells to selenite.

Polyamines in rat liver during experimental inflammation

The effect of turpentine, a chemical inflammatory agent, on polyamine synthesis has been studied. Ornithine decarboxylase activity is markedly increased in liver 6 hrs after subcutaneous injection of turpentine, and then decreases. No significant modification is observed in S-adenosylmethionine decarboxylase. Putrescine injected prior to turpentine prevents this increase. Putrescine, spermidine and spermine concentrations are all increased following turpentine, but with different patterns: spermidine alone keeps increasing for 50 hours. Putrescine and spermidine injected prior to turpentine partially counteract the increase of serum alpha 2-macroglobulin, which is believed to be a marker of inflammation.

Selenium and polyamine metabolism: different effect of selenite on liver and bursa of Fabricius ornithine decarboxylase activity

1. When injected i.p., sodium selenite promoted a marked increase of rat liver ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) activities; when administered with the diet for 6 weeks, a less marked increase in liver ODC was observed, whereas SAMDC was not significantly changed. 2. Protein synthesis was involved in the observed modifications. The rate of ODC inactivation was also changed. 3. ODC increase was accompanied by an enhanced putrescine concentration in liver. 4. A marked increase of ODC, accompanied by an enhancement of putrescine, was promoted by selenite (i.p.) also in chicken liver, together with an enhancement of glutathione concentration. Spermidine acetyltransferase (SAT) was also increased. 5. In the bursa of Fabricius, SAT activity was also increased, whereas ODC was decreased. However the expected modifications in polyamine concentration were not observed. 6. Decrease of ODC activity in the bursa was not due to an antizyme. 7. In vitro, selenite concentrations known to inhibit cell proliferation (greater than 1 microgram/ml) inhibited both ODC and SAT activities; at lower concentration, SAT activity was enhanced.

Effect of vanadate and pyridoxal phosphate on S-adenosylmethionine

Vanadate in the presence of pyridoxal phosphate promotes the decarboxylation of S-adenosylmethionine. Pyridoxal has a lower effect; pyridoxine none. The rate of decarboxylation depends on pyridoxal phosphate and vanadate concentration. Vanadate as low as 10(-7) M gives significant decarboxylation. The reaction seems to occur through the formation of a Schiff base. The spectral shift elicited by S-adenosylmethionine on pyridoxal phosphate due to the presence of the sulfonium function is influenced by vanadate. Orthovanadate is a little less effective then metavanadate; vanadyl sulfate is even less efficient, and the effect of Cu2+ at the same concentration is still lower. Bleomycin partially prevents the vanadium effect. In vivo, vanadate promotes a marked increase in chicken liver S-adenosylmethionine and S-adenosylhomocysteine concentration, whereas the polyamine concentration is unaffected.

Muscarinic receptors: evidence for a nonuniform distribution in tracheal smooth muscle and exocrine glands

Muscarinic receptor distribution in smooth muscle, exocrine glands, and epithelium of the ferret trachea was determined using [3H]propylbenzilylcholine mustard ([3H]PrBCM) binding and autoradiography. Specific, atropine-sensitive [3H]PrBCM binding was quantified autoradiographically in the trachealis muscle (approximately 21 binding sites/microns2), surface epithelium (approximately 6 binding sites/microns2), and submucosal glands (approximately 5 binding sites/microns2). Serous and mucous cells in the glands did not differ in receptor density. Binding sites on gland and epithelial cells were associated with basolateral membranes. In the trachealis muscle, a gradient in receptor density was observed, with outer layers of muscle containing 3 to 10 times more receptors per unit area than inner layers. Receptor distribution in both glands and muscle paralleled the distribution of cholinergic axons. However, at the light microscope level, there was no evidence for the presence of receptor "hot spots" related to the position of individual axons. The parallelism in the distribution of axons and receptors suggests the possibility of neural control of the genesis and/or maintenance of receptor distribution in these tissues.

Activity of some enzymes involved in the metabolism of polyamines in the liver of streptozotocin-diabetic rats

The effect of diabetes on some enzymes of polyamine metabolism was studied in male rats 1-12 days after administration of streptozotocin. Hepatic ornithine decarboxylase activity decreased in the first days after the administration, but increased thereafter. The decrease was not due to an alteration of the ODC-antizyme concentration, nor to a posttranslational modification catalyzed by transglutaminase. S-adenosylmethionine decarboxylase and ornithine transaminase were both increased. Spermidine acetyltransferase activity was practically unchanged, while its inactivating factor was markedly decreased.

Acetylation of polyamines in chicken brain and retina

Both spermidine and spermine are acetylated in chicken brain and retina. From spermidine, more N1-acetylspermidine than N8-acetylspermidine is formed by both the brain and the retinal cytosol. Km for spermidine is similar with the enzyme preparation of the two tissues, but that for spermine is lower with the retinal preparation. Both tissues contain an activity able to reduce spermidine acetyltransferase activity. Both alkaline phosphatase and cAMP-dependent protein kinase (catalytic subunit) are able to inactivate the spermidine acetyltransferase activity of both tissues. Spermidine acetyltransferase activity and polyamine levels have been measured in both brain and retina during embryonic life. Only in the last part of the development can enzyme activity be correlated with the retina spermidine and spermine concentration.

Regulation of ornithine decarboxylase: studies on the effect of insulin and diaminopropane on transglutaminase activity

Transglutaminase activity measurements in the liver of insulin- and diaminopropane treated chickens showed that insulin enhances activity in the supernatant, but has no effect on the nuclear fraction. In the absence of exogenous Ca++ ions, both fractions were more active, showing that insulin promotes an increase in the available Ca++ ions. No modification was observed after diaminopropane. It follows that changes in ornithine decarboxylase activity previously observed under these conditions are not dependent on transglutaminase activity.

Regulation of spermidine acetyltransferase activity by phosphorylation and dephosphorylation

Spermidine acetyltransferase activity is more than 10-fold higher in the pancreas of a 20-hr-fasted than in that of a fed chicken. The preparation of the fed bird inactivates the other. The effect is due to a thermolabile component of microsomes, and is also obtained with alkaline phosphatase. The inactivated preparation partially recovers its activity through phosphorylation catalyzed by a cAMP-dependent protein kinase. The results presented strongly suggest that spermidine acetyltransferase activity is regulated by phosphorylation and dephosphorylation.

Neutral red stains ganglia in the vagal motor pathway to ferret trachea without affecting ganglionic transmission

To determine the effect of Neutral red (0.01%) on neural transmission through ganglia, we used an in vitro nerve-muscle preparation of ferret trachea. Before, during, and after incubating the trachea in Neutral red, we induced isometric muscle contractions first by activating preganglionic fibers with electrical stimulation of the vagus nerve, and then by activating postganglionic nerve fibers with electrical field stimulation. Incubation in Neutral red (0.01%) for 45 min at 38 degrees C reduced the responses to both pre- and postganglionic activation. When the control responses to pre- and postganglionic activation were matched. Neutral red depressed the 2 responses to the same degree, implying that the depression was confined to postganglionic structures. Washout of Neutral red from the medium restored the responses to both pre- and postganglionic activation. Histologic examination of all tissues proved that the ganglia were still stained after the washout procedure. We conclude that Neutral red (0.01%) depresses smooth muscle contractions evoked through neural pathways, and that this depression is reversible and confined to postganglionic structures, leaving ganglionic transmission intact.

Ornithine decarboxylation in rat liver nuclei

1. Decarboxylation of ornithine in rat liver cytosol produces putrescine; on the contrary, no putrescine is formed in nuclei. 2. In nuclei, decarboxylation is not inhibited by alpha-difluoromethylornithine and depends on NADH reoxidation. This shows that decarboxylation occurs after transamination of ornithine. 3. The increase of ornithine transaminase activity may be partially responsible for the enhanced decarboxylation after 1-methyl-3-isobutylxanthine administration. Data obtained in the presence of Ca2+ suggest that modification of nuclear Ca2+ concentration may also be responsible.

Arginase, ornithine decarboxylase and S-adenosylmethionine decarboxylase in chicken brain and retina

Arginase, ornithine decarboxylase and S-adenosylmethionine decarboxylase are active in both retina and brain. Activity is higher in cerebellum than in the cerebral hemispheres and optical lobes. Arginase and ornithine decarboxylase are very active in the retina of very young chicks, while S-adenosylmethionine decarboxylase is poorly active. By contrast, S-adenosylmethionine decarboxylase is much more active in brain. The pattern of activity during development is different; only ornithine decarboxylase is very active during embryonal life; S-adenosylmethionine decarboxylase, at all events in brain, is more active in adult life. Ornithine decarboxylase is inhibited in vitro by alpha-difluoromethylornithine, but not in vivo. Diaminopropane inhibits brain ornithine decarboxylase, but does not induce an ornithine decarboxylase-antizyme. Methylglyoxal bis(guanylhydrazone) promotes an increase of S-adenosylmethionine decarboxylase activity in both the brain and the retina in vivo.

Induction of an ornithine decarboxylase-antizyme by diaminopropane in chicken kidney and intestinal mucosa

Administration of diaminopropane to chickens, injected with insulin in order to induce ornithine decarboxylase, prevents the increase of the decarboxylase activity in kidney and in the intestinal mucosa, not in the heart, In the first two tissues, not in the last one, an ornithine decarboxylase-antizyme is detected. The ornithine decarboxylase-antizyme appears therefore to be involved in vivo in the regulation of ornithine decarboxylase activity.

Catabolism of ornithine in chicken liver

It is shown that most ornithine in a chicken liver homogenate is decarboxylated in the particulate fraction. This fraction, however, requires the cytosol for complete activity. The dialyzed supernatant does not activate decarboxylation of ornithine, while the supernatant is more effective when previously inactivated at 100 degrees C. The supernatant can be substituted by the intermediates of the citric acid cycle (oxaloacetate, citrate, succinate, malate), by pyruvate, and partially by ADP as well. Rotenone blocks decarboxylation suggesting that this occurs through the pathway ornithine leads to glutamic semialdehyde leads to glutamate leads to alpha-ketoglutarate, which in turn is decarboxylated. The activating metabolites would thus have a role in reoxidizing NADH, and the ketoacids also in supplying the acceptor for transamination of glutamate, and indirectly for ornithine transamination. Pyruvate and oxaloacetate do not transaminate with ornithine. Insulin promotes a marked increase of cytosol ornithine decarboxylase activity, but has little effect on decarboxylation by the particulate cellular fraction.

S-Adenosylmethionine decarboxylase in liver, heart and pancreas of pyridoxine-deficient chickens

S-adenosylmethionine decarboxylase activity has been measured in liver, heart and pancreas of pyridoxine-deficient chickens: in liver and heart muscle it is increased, while in pancreas the activity is unchanged with respect to control animals. Insulin induced activity in liver and in heart muscle of normal as well as of pyridoxine-deficient chickens, while in the pancreas an induction was observed in the control animals and a decrease in the deficient ones. These data appear to rule out any involvement of pyridoxal phosphate in the reaction catalyzed by S-adenosylmethionine decarboxylase.

Urea cycle enzymes in the liver of a dolphin Platanista indi

Urea cycle enzymes are all shown to be active in dolphin liver. Acetylglutamate-independent cytoplasmic carbamylphosphate synthase is also present. Arginase is a basic protein, although less markedly basic than the dog enzyme. It is 118 per cent activated by heating at 50 degrees. Optimum pH is 10.5. Co++ and Ni++ inhibit the enzyme. AMP deaminase, glutamicoxaloacetic transaminase, glutamate dehydrogenase and ornithine transaminase are also active in dolphin liver.

Carbamylphosphate hydrolysis in donkey liver

Mitochondria, microsomes, and cytosol all hydrolyze carbamylphosphate. Microsomes show the greatest specific activity. The mitochondrial enzyme is localized in the inner membranes, has optimum pH 5.5 and is heat-stable; the cytosol enzyme has optimum pH 5.0 and is heat-labile. Km for carbamylphosphate is 1.1 to 1.2 X 10(-2 M for both the cytosol and the mitochondrial enzyme. Both enzymes are inhibited by high substrate concentrations.