Stimulation Of Ornithine Decarboxylase Activity Research Articles

Inhibition of cytomegalovirus-stimulated human cell ornithine decarboxylase by α-difluoromethylornithine

1. The relationship between synthesis of putrescine, human cytomegalovirus DNA synthesis, cell DNA synthesis, and human cytomegalovirus replication has been studied. 2. Stimulation of ornithine decarboxylase activity by shifting low serumarrested whole human embryo cells to high serum medium is inhibited more than 99% by 2.5 mM dl-α-difluoromethylornithine. The addition of dl-α-difluoromethylornithine to human cells arrested in low serum and subsequently stimulated by the addition of fresh high serum-containing medium, causes a greater percent inhibition of ornithine decarboxylase activity than when the drug is added to growing human cells. 3. Increased ornithine decarboxylase activity produced by infection of low serum-arrested human cells was inhibited by 5.0 mM of dl-α-difluoromethylornithine. However, at a concentration of 5.0 mM, neither dl-α-methylornithine nor dl-α-difluoromethylornithine affected human cytomegalovirus growth or was toxic to these cells. These data suggest that the increased putrescine synthesis produced by infection is not required for virus replication. 4. The addition of 5.0 mM dl-α-difluoromethylornithine had no effect on human cytomegalovirus DNA synthesis or human cytomegalovirus-induced stimulation of cell DNA synthesis. However, 5.0 mM dl-α-difluoromethylornithine significantly reduced the stimulation of cell DNA synthesis caused by treatment with mock infecting fluid.

Effects of Epidermal Growth Factor, Fibroblast Growth Factor and Bovine Serum Albumin on Ornithine, Decarboxylase Activity of Porcine Granulosa Cells

Epidermal growth factor, a potent mitrogen for granulosa cells produced a three-fold stimulation of ornithine decarboxylase activity in porcine granulose cells in vitro. Fibroblast growth factor, another compound with mitogenic activity for granulose cells, did not stimulate ornithine decarboxylase. Maximally effective concentrations of a commercial preparation of bovine serum albumin equalled the maximal effect of epidermal growth factor on this enzyme activity. The dominant stimulator(s) in the albumin preparation eluted after bovine serum albumin in gel filtration. At maximally effective concentrations, luteinizing hormone produced substantially greater stimulation than either epidermal growth factor or the bovine albumin preparation. Combinations of saturating doses of any two of these stimulators produced additive effects on enzyme activity.

Effects of 1,3-diaminopropane on testosterone induced hypertrophy and polyamine synthesis in mouse kidney.

The effects of prolonged treatment with 1,3-diaminopropane, a structural analogue of putrescine, on polyamine metabolism and growth in kidney tissue, were studied in mice in which renal hypertrophy was induced by testosterone treatment. Injections of 1,3-diaminopropane resulted in an almost total suppression of the testosterone induced stimulation of ornithine decarboxylase activity and prevented the accumulation of putrescine and spermidine in the kidneys. Renal spermine concentration was even lowered. Administration of 1,3-diaminopropane effectively prevented the testosterone induced increase in renal weight and RNA. In mice receiving 1,3-diaminopropane proteinuria was observed and histological examination revealed renal damage. Due to the nephrotoxic action of 1,3-diaminopropane caution is essential in relating the prevention of renal hypertrophy and the inhibition of polyamine synthesis.

Effect of Follicle-Stimulating Hormone and Its Antiserum on the Activity of Ornithine Decarboxylase in the Ovary of Rat and Hamster*

The ability of FSH to stimulate the activity of ornithine decarboxylase (ODC) in the ovary of the immature rat and cycling hamster has been examined using specific antisera to gonadotropins. The stimulatory effect of FSH on ODC activity in the ovary of the immature rat was abolished when LH antiserum was administered along with FSH, while similar administration of FSH antiserum had no effect on LH action in stimulating ODC activity, thereby demonstrating the specificity of the LH effect. During the estrus cycle of the hamster, ODC activity in the ovary could be detected only on the evening of proestrus, the maximal activity seen at 1700 h being associated with both the Graafian follicles and the rest of the ovarian tissue. Neutralization of the proestrous FSH surge had no effect on the activity of ODC in either of these tissues, while similar administration of LH antiserum at 1300 h of proestrus completely inhibited the ODC activity in both large follicles and the rest of the ovarian tissue. Thus, the surge of LH, but not of FSH, appears to be responsible for regulating the ODC activity in the ovary of the cycling hamster.

Selective inhibition by interferon of serum-stimulated biochemical events in 3T3 cells

We examined the effect of mouse interferon on the stimulation of [ 86Rb +] uridine, 2-deoxyglucose and Pi uptake and of ornithine decarboxylase activity produced by serum in quiescent cultures of Swiss 3T3 cells. We found that interferon causes a differential dose-dependent inhibition of the stimulation of ornithine decarboxylase activity and the second phase of Pi uptake. Other protein-synthesis independent or dependent events are not affected.

Regulation of Ornithine Decarboxylase Activity in Rat Ovarian Cells in Vitro

Incubation of rat ovarian cell suspension with human choriogonadotropin (hCG) caused a marked enhancement of ornithine decarboxylase (EC 4.1.1.17) activity after a lag period of several hours. Even though ovarian ornithine decarboxylase could be induced in minimum essential medium by the hormone alone, supplementation of the medium with various sera greatly enhanced the stimulation of the enzyme activity. All the sera tested (human, fetal calf and horse) were able to stimulate ornithine decarboxylase activity even in the absence of hCG. Maximum stimulation of the enzyme activity by hCG and/or serum occurred in ovarian cell suspensions prepared from 30 to 33-day-old rats. There was a close correlation between the stimulation of ornithine decarboxylase activity and the accumulation fo cyclic AMP in response to the administration of the hormone (in the presence or absence of serum). However, while various sera alone markedly enhanced ovarian ornithine decarboxylase activity in vitro they, if anything, only marginally stimulated the accumulation of cyclic AMP and the secretion of progesterone in ovarian cells in the absence of gonadotropin. A similar dissociation of the stimulation of ornithine decarboxylase activity from the production of cyclic AMP and progesterone was likewise found when the ovarian cells were incubated in an enriched medium (M199) supplemented with albumin and lactalbumin hydrolysate in the absence of the hormone. Under these culture conditions ornithine decarboxylase activity was strikingly enhanced, greatly exceeding the stimulation obtained with various sera, while the accumulation of cyclic AMP and the secretion of progesterone remained virtually unchanged. Specific inhibition (up to 90%) of gonadotropin-induced ornithine decarboxylase activity by difluoromethyl ornithine or 1,3-diamino-2-propanol had little effect on the ability of the ovarian cells to respond to the hormone with increasing production of cyclic AMP and progesterone. While showing that rat ovarian ornithine decarboxylase can be induced in vitro by choriogonadotropin or various sera, our results indicate that the activation of the enzyme involves at least two different mechanisms: (i) One (in response to gonadotropin) involving a prior stimulation of cyclic AMP production, and (ii) another (in response to serum) that is not associated with increases in the accumulation of the cyclic nucleotide.

Multiplication Stimulating Activity Regulates Ornithine Decarboxylase in Isolated Porcine Granutlosa Cells in Vitro

The polypeptide growth factor, multiplication stimulating activity (MSA), stimulates ornithine decarboxylase (ODC) activity in isolated porcine granulosa cells maintained under chemically defined conditions in vitro. The stimulatory action of MSA is saturable, and dose-dependent (0.1-1000 ng/ml). MSA effects are additive to those of luteinizing hormone (LH), but not those of follicle stimulating hormone (FSH). Stimulation of ODC activity by MSA requires cellular protein and RNA synthesis, and appears to be mediated independently of cyclic AMP. These observations provide the first demonstration of MSA action in the mammalian ovary.

6-Hydrxydopa-induced stimulation of ornithine decarboxylase activity in the developing rat brain.

The developmental alteration in the specific activity of ornithine decarboxylase (ODC) was investigated in the brain of rats treated with 6-hydroxydopa (6-OHDOPA) at birth. The specific activity of ODC in the cerebral hemispheres, brain stem and cerebellum declined from high level on day 4 to the non-detectable level in the adult. The neonatal treatment with 6-OHDOPA (75 mg/kg, s. c., 3 days) produced the rapid increase of ODC activity in the cerebral hemispheres and the brain stem in the 4- and 5-day-old rat. An injection of 6-OHDOPA appears to affect cellular activity of catecholamine neurons and glial cells in the developing brain.

Calcium, asparagine and cAMP are required for ornithine decarboxylase activation in intact Chinese hamster ovary cells

Asparagine specifically activated ornithine decarboxylase activity 5–7 fold by 7–8 h in confluent cultures maintained with a salts/glucose medium. When dibutyryl cAMP was added with asparagine, a 40–50 fold stimulation of ornithine decarboxylase activity was produced. Ornithine decarboxylase activation in the salts/glucose medium was not sensitive to actinomycin D. Omission of Ca ++ and Mg ++ from the medium abolished the ability of asparagine and/or dibutyryl cAMP to stimulate enzyme activity. Calcium was essential for the asparagine and dibutyryl cAMP mediated stimulation of ornithine decarboxylase activity.

Epidermal Growth Factor Stimulates Ornithine Decarboxylase Activity in the Digestive Tract of Mouse

SummaryThis study examined the effect of EGF (6 μg g-1 body wt, subcutaneously) on OD concentration in stomach, duodenum, midgut and colon, as well as a control tissue, heart, in 8-day-old mice. The animals were killed 4 hr after either EGF or control water injections. OD activity, expressed as picomoles of 14CO2 liberated from 1-[14C]l-ornithine per mg wet weight tissue, was significantly higher in the animals given EGF than in controls in the stomach (EGF 29.9 ± 6.8; control 9.9 ± 3.6, P < .05) and the duodenum (EGF 51.7 ± 16.9; control 6.5 ± 4.3, P < .05) but not in the midgut, colon or heart. It is concluded that epidermal growth factor stimulated ornithine decarboxylase activity in the stomach and duodenum of neonatal mice suggesting a possible role for EGF (or urogastrone) in mucosal repair and defense in these tissues.

Prostaglandin stimulation of ovarian ornithine decarboxylase [formula omitted

Prostaglandins E 1 and E 2 caused a 5–10 fold stimulation of ornithine decarboxylase activity in granulosa cells isolated from porcine ovarian follicles. The minimally effective concentration of prostaglandin E 2 was 10 ng/ml and the plateau of activity was reached at 500 ng/ml. Prostaglandin F 2α was ineffective. 1-Methyl,3-isobutyl-xanthine, a phosphodiesterase inhibitor, potentiated the effect of both submaximal and maximal effective doses of prostaglandin E 2, suggesting that the effect of prostaglandin E 2 is mediated by cAMP. The effect of prostaglandin E 2 was similar to that of luteinizing hormone and a cAMP analogue, 8-Bromo-cAMP.

Effects of thyroid state on ornithine decarboxylase activity of the adenohypophysis of the rat and chicken

In White Leghorn chickens, 0.5 ng/kg of thyrotropin-releasing hormone (TRH) increased ornithine decarboxylase activity in the rostral lobe of the adenohypophysis without any alteration of enzyme activity in the caudal lobe. In rats, administration of TRH (250 ng/100 g body weight) increased thyroid-stimulating hormone (TSH) release but did not increase ornithine decarboxylase activity in the adenohypophysis. However, surgical thyroidectomy performed on rats resulted in declining levels of T 3 and T 4 in the plasma, an increase in the plasma level of TSH, and a twofold increase in ornithine decarboxylase activity in the adenohypophysis. In the chicken, administration of both methimazole and thyroxine caused elevated ornithine decarboxylase activity in the rostral and caudal lobes of the adenohypophysis. The hormone stimulation of ornithine decarboxylase activity, an early indicator of new biosynthesis, is suggested as a marker to study control mechanisms in the adenohypophysis.

Ovine placental lactogen stimulation of ornithine decarboxylase activity in brain and liver of neonatal rats

Ovine placental lactogen (oPL), growth hormone (oGH), prolactin (oPRL) and human placental lactogen (hPL) were administered intracisternally (ic) or intraperitoneally (ip) to 17 day old rats and brain and liver ODC activities determined four hours later. When given ic, oPL, oGH and oPRL caused significant increases in brain ODC activity, while hPL had no significant effect. After ip administration, oPL and oGH also caused a significant increase in brain as well as liver ODC activity but oPRL and hPL were without significant effect. The stimulation of polyamine metabolism by oPL together with earlier reports of its potent somatotropic effects and its high concentration in the fetus supports the hypothesis that oPL may be important in the regulation of fetal growth.

The effects of isoproterenol on taurine concentration in the rat heart

Administration of the β-agonist isoproterenol to rats caused a sharp increase in the influx rate of taurine into the heart, but had no effect on the rate of biosynthesis of taurine in the heart. Influx rates of other amino acids were also stimulated, the distribution ratios, (dpm/g heart)/(dpm/ml plasma), of β-amino acids being 3–4 times higher than α-amino acids. The doses of isoproterenol employed induced cardiac hypertrophy, but the stimulation of taurine influx appeared to be an independent phenomenon, in that near maximum stimulation of influx was achieved prior to stimulation of ornithine decarboxylase activity. Reserpine treatment also produced stimulation of taurine influx with no effect on biosynthesis. These results indicate a close connection between increased sympathomimetic activity and increased influx of amino acids.

Stimulation of ornithine decarboxylase by relaxin

Relaxin, a protein hormone of pregnancy, stimulated ornithine decarboxylase activity (EC 4.1.1.17) in two of its target tissues. Both the mouse public symphysis and uterus respond to a single injection of relaxin; within 2–4 hours after hormonal treatment of the mice, ornithine decarboxylase activity was observed to increase 2–8 fold over control levels. This increase in enzymatic activity may represent one step in the mechanism by which relaxin exerts its effects.

In VitroStimulation of Thyroid Ornithine Decarboxylase Activity and Polyamines by Thyrotropin*

Thyrotropin (TSH) stimulation of ornithine decarboxylase (ODC) activity and polyamine levels was studied in vitro in rat thyroids. The elevation in ODC activity was related to the concentration of TSH in the incubation medium with peak activity at a concentration of 25mU/ml. ODC activity with 50 mU/ml of TSH was 3 to 5-fold higher than control activity at 5 h of incubation; this stimulation was enhanced by the addition of 0.5 mM 3-isobutyl-l-methyl xanthine (MIX), a phosphodiesterase inhibitor. Dibutyryl cyclic AMP (DbcAMP) also stimulated ODC activity with a dose response up to 2.0 mm. The increase in ODC activity with TSH and MIX was prevented by incubation with actinomycin D (10 microgram/ml) or puromycin (0.2 mM). Putrescine concentrations in rat thyroids rose to three times basal levels after 6 h of incubation with TSH and MIX; no significant elevation in spermidine or spermine was observed after up to 7 h incubation. The increase in tissue putrescine preceded a rise in [3H]uridine incorporation into acid-soluble material that occurred at 7 h. The results suggest that stimulation of thyroid ODC activity by TSH is mediated by a cyclic AMP; the data further are consistent with a role for polyamines in the control of RNA synthesis in the thyroid.

Tissue-specific stimulation of ornithine decarboxylase activity by pituitary factors immunologically related to growth hormone.

Ornithine decarboxylase (L-ornithine carboxylase, EC 4.1.1.17) is an important enzyme in polyamine synthesis. Its activity is influenced by several peptides hormones, including growth hormones, which have physiological significance in various growth situations. A crude ovine pituitary growth hormone preparation (NIH-GH-S10) was subjected to gel exclusion chromatography (Sephadex G-100) and two major fractions were obtained. One of these corresponded to dimeric growth hormone (GH). The other fraction was excluded by the gel matrix, suggesting a material of higher molecular weight than GH. This was confirmed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Analysis of a high molecular weight fraction by radioimmunoassay (antisera prepared against GH) and by bioassay (weight gain in hypophysectomized rats) gave apparent GH contents of 19% and 6%, respectively. On a weight basis, the high molecular weight fraction was more effective than GH in stimulating the activity of hepatic and adrenal ornithine decarboxylase, but GH was more effective in stimulating renal ornithine decarboxylase activity. Subfractionation of the high molecular weight fraction using a high porosity gel (Sephadex G-200) gave four fractions, which were shown by amino acid analysis and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate to be distinct from GH and heterogenous. These subfractions had different potencies for stimulating renal and hepatic ornithine decarboxylase activity. The ability of crude growth hormone preparations to stimulate ornithine decarboxylase activity in some tissues may be a function of pituitary factors, in addition to GH, which have minimal growth promoting activity.

Stimulation of ornithine decarboxylase activity in chick fibroblasts by non-suppressible insulin-like activity (NSILA), insulin and serum.

A factor isolated from human serum (nonsuppressible insulin-like activity, NSILA) stimulates multiplication of serum-starved chick embryo fibroblasts and stimulates activity of ornithine decarboxylase (ODC). Physiological doses of NSILA (200 muU/ml) and pharmacological doses of insulin (200 mU/ml) stimulate ODC 4-5-fold, 10% fetal calf serum about 18-fold. Combined addition of NSILA and insulin does not result in higher activities, suggesting a common mechanism of action. The increase in cell number obtained with NSILA, insulin or serum parallels the degree of ODC stimulation. Treatment of cells with pronase also stimulates ODC activity. A sharp increase in ODC activity occurs between 2, 5 and 5.0 hours after addition of the growth factors with a peak at 4.0-4.5 hours ("activation period"). As cells leave G1 phase, ODC activity decreases rapidly. To achieve maximal activity of ODC, the growth factors have to be present during the entire "activation period." The potential to reactivate ODC decreases as cells pass through S phase. Results obtained using cycloheximide suggest that ODC is translated only in the second half of the "activation period." Data on effects of dbcAMP and dbcGMP on ODC activation by serum are discussed.

Inhibition of ornithine decarboxylase activity and spermidine accumulation in regenerating rat liver.

Injections of 1,3-diaminopropane, a close structural analogue of putrescine (1,4-diaminobutane), into partially hepatectomized rats powerfully inhibited ornithine decarboxylase (EC 4.1.1.17) activity in the regenerating liver in vivo . The compound did not have any effect on the enzyme activity in vitro (under assay conditions employed) but appeared to exert an inhibitory influence on the synthesis of ornithine decarboxylase itself. Repeated injections of diaminopropane into rats after partial hepatectomy, starting at the time of the operation and continued until 33 h postoperatively, markedly diminished the stimulation of ornithine decarboxylase activity in the regenerating liver remnant, and completely prevented the increases in hepatic spermidine concentration normally occurring in response to partial hepatectomy. Treatment of the rats with diaminopropane did not depress the activity of adenosylmethionine decarboxylase (EC 4.1.1.50) in the regenerating liver. Nor did the compound have any effect, whatsoever, on the activity of spermidine synthase (EC 2.5.1.16) in vitro , thus obiviously proving that the increased accumulation of liver spermidine after partial hepatectomy primarily depends upon a stimulation of ornithine decarboxylase activity and a concomitant accumulation of putrescine. The results also showed that 1,3-diamino-propane could not replace putrescine in the synthesis of higher polyamines in rat liver. The inhibition of ornithine decarboxylase by diaminopropane thus appears to represent “gratuitous” repression of polyamine biosynthesis and might conceivably be used for studies devoted to the elucidation of the physiological functions of natural polyamines.

Human pituitary growth hormone. 44. Effects of plasmin-modified hormone and its fragments on ornithine decarboxylase activity and lipolysis.

The rat hepatic ornithine decarboxylase stimulating activity of plasmin-modified human growth hormone and its two peptide fragments has been investigated. The activity was completely retained after plasmin treatment. The NH2-terminal fragment [Cys (Cam)53-HGH-(1-134)] retained 10% of the activity, whereas the COOH-terminal fragment [Cys (Cam) 165, 182, 189-(141-191)] was not active. The lipolytic activity of human growth hormone was greatly reduced after plasmin treatment, as examined in isolated rabbit adipocytes. It is suggested that the structural requirements for the lipolytic activity of the hormone are different from those required for stimulation of ornithine decarboxylase activity.