Ornithine decarboxylase activity in developing rat brain

—Total ornithine decarboxylase (ODC) (EC 4.1.1.17) activity per rat brain was elevated markedly from 14 days after conception to 12 days postnatum. ODC activity in the brainstem was very low and changed little during postnatal development. Activity in the cerebral hemispheres declined from a high level at birth to the low adult level by 8 days postnatum. Conversely activity in the cerebellum increased markedly from 3 days until 11 days postnatum, then suddenly decreased. Hence, the periods of greatest ODC activity paralleled those of maximal cell proliferation in each brain region. During perinatal brain development ODC activity changed considerably; it declined at about one day prior to term, and then increased rapidly to its highest level of activity at 4 h postnatum. Premature birth by caesarian section or lack of maternal care and nutrition did not affect this early postnatal response. The postnatal burst in ODC activity appears to be unique for brain tissue, since this response did not occur in heart, skeletal muscle or liver. Data from studies in which portions of fractions characterized by high or low enzymatic activity, respectively, were mixed or in which the supernatant enzyme fraction was dialysed are not consistent with the presence of direct inhibitors or activators of the enzyme. In addition, administration of cycloheximide to newborn rats abolished the 4-h postnatal burst in ODC activity. Our results suggest that the increase in ODC activity reflects enzyme synthesis de novo.     

Ornithine decarboxylase activity in regenerating rat adrenal cortex

The activity of ornithine decarboxylase during the regenerating process of adrenal cortex was evaluated in Sprague-Dawley male rats weighing 140–180 g. In this study, 4 groups of rats were enucleated and another 4 groups were sham operated. Animals were maintained at a temperature of 23 ± 1°C and 12:12 h light:dark cycle. At 7 and 11 days post surgery, animals were sacrificed at 0600 h and 1800 h, respectively. Adrenal glands were immediately removed and assayed for ornithine decarboxylase (ODC). The enzyme activity was found to be significantly elevated in enucleated groups as compared to the sham control groups at the 7th and the 11th day of surgery. ODC activity was found to be about 2 times higher at 1800 h by the 7th day and 5 times higher at 1800 h by the 11th day of adrenal surgery when compared to the activity at 0600 h. From these results, it appears that ODC activity not only increases as the regeneration process of adrenal cortex approaches completion, but also becomes more pronounced towards the end of the light period.     

Ornithine decarboxylase activity in rat organs and tissues under artificial hypobiosis

The influence of hypothermia-hypoxia-hypercapnia on ornithine decarboxylase (ODC, EC 4.1.1.17) activities in rat organs and tissues and also on the thymocyte distribution throughout the cell cycle stages was studied. The state of artificial hypobiosis in rats on decrease in the body temperature to 14.4–18.0°C during 3.0–3.5 h was accompanied by drops in the ODC activities in the neocortex and liver by 50–60% and in rapidly proliferating tissues (thymus, spleen, and small intestine mucosa) by 80% of the control value. In kidneys the ODC activity raised to 200% of the control level. Twenty-four hours after termination of the cooling and replacing the rats under the standard conditions, the ODC activities in the neocortex, liver, kidneys, spleen, and intestinal mucosa returned to the control values, but remained decreased in the thymus. Forty-eight hours later the ODC activities in the thymus and spleen exceeded the normal level. The distribution of thymocytes throughout the cell cycle stages did not change in rats in the state of hypothermia (hypobiosis); 24 and 48 h after termination of the cooling the fraction of thymocytes in the S stage was decreased and the fraction of the cells in the G₀+G₁ stage was increased. The normal distribution of thymocytes throughout the cell cycle stages recovered in 72 h. Thus, in the thymus the diminution of the ODC activity preceded the suppression of the cell proliferation rate. The tissue-specific changes in the ODC activity are suggested to reflect adaptive changes in the functional and proliferative activities of organs and tissues during the development of hypobiosis under conditions of hypothermia-hypoxia-hypercapnia.     

Ornithine decarboxylase activity during neonatal development of the rat ventral prostate

The relationship between ornithine decarboxylase activity and growth has been examined in ventral prostates from rats aged 2–60 weeks. The incorporation of [¹²⁵I]iododeoxyuridine in vitro was used to assess DNA-synthetic activity. During 2–7 weeks post-partum ornithine decarboxylase activity/prostate and the protein content and wet weight increased exponentially. In contrast, the incorporation of [¹²⁵I]iododeoxyuridine/prostate fell during the first 4 weeks. This decline was reversed at about the time when the systemic concentrations of gonadal androgens start to rise. After 10 weeks post-partum the incorporation of [¹²⁵I]iododeoxyuridine/prostate and ornithine decarboxylase activity/prostate levelled off, whereas the DNA and protein content of the prostate contonued to increae at a slow rate.     

Ornithine decarboxylase: a biochemical marker of repair in damaged tissue

The purpose of this study was to: (a) determine the temporal pattern of expression of ornithine decarboxylase (ODC), an established marker of cells engaged in proliferation and differentiation, during repair of traumatized skeletal muscle, and (b) evaluate ODC as a biochemical marker for indexing the extent and rate of repair of traumatized skeletal muscle in response to therapeutic agents. Adult female Wistar rats weighing 240 to 280 grams were anesthetized and injected with 100 ul of 2% lidocaine into the right or left anterior tibialis muscle to induce a localized injury. The animals were treated 1 hour post-injection and every 12 hours for five minutes up to the time of sacrifice using ultrasonic irradiation at 1.5 watts/cm2, sham-irradiation, or no treatment. An analysis of variance for repeated measures and a Tukey's post hoc test were used to determine the significance of treatment effects. Animals irradiated with ultrasound demonstrated an accelerated pattern of change in ODC activity at 24 hours (P less than 0.001), 30 hours (P less than 0.003), and at 48 hours (P less than 0.002) compared to control and sham-irradiated animals at these time intervals. Irradiated animals also demonstrated less edema at 48 hours compared to sham-irradiated and control animals (P less than 0.003). These findings suggest that ODC is a useful biochemical marker for determining the extent and rate of tissue repair in traumatized skeletal muscle, and it provides a temporal and quantifiable parameter for evaluating the efficacy of therapeutic agents used to treat damaged skeletal muscle.     

Ornithine decarboxylase activity in rat tissues in the late periods after irradiation

Ornithine decarboxylase activity in some rat tissues was shown to grow at remote times after gamma irradiation (60Co) with nonlethal doses. The authors suggest that ornithine decarboxylase activity should be used as a biochemical marker of remote effects of ionizing radiation.     

Ornithine decarboxylase activity in insulin-deficient states

The activity of ornithine decarboxylase, the rate-controlling enzyme in polyamine biosynthesis, was determined in tissues of normal control rats and rats made diabetic with streptozotocin. In untreated diabetic rats fed ad libitum, ornithine decarboxylase activity was markedly diminished in liver, skeletal muscle, heart and thymus. Ornithine decarboxylase was not diminished in a comparable group of diabetic rats maintained on insulin. Starvation for 48h decreased ornithine decarboxylase activity to very low values in tissues of both normal and diabetic rats. In the normal group, refeeding caused a biphasic increase in liver ornithine decarboxylase; there was a 20-fold increase in activity at 3h followed by a decrease in activity, and a second peak between 9 and 24h. Increases in ornithine decarboxylase in skeletal muscle, heart and thymus were not evident until after 24–48h of refeeding, and only a single increase occurred. The increase in liver ornithine decarboxylase in diabetic rats was greater than in normal rats after 3h of refeeding, but there was no second peak. In peripheral tissues, the increase in ornithine decarboxylase with refeeding was diminished. Skeletal-muscle ornithine decarboxylase is induced more rapidly when meal-fed rats are refed after a period without food. Refeeding these rats after a 48h period without food caused a 5-fold increase in ornithine decarboxylase in skeletal muscle at 3h in control rats but failed to increase activity in diabetic rats. When insulin was administered alone or together with food to the diabetic rats, muscle ornithine decarboxylase increased to activities even higher than in the refed controls. In conclusion, these findings indicate that the regulation of ornithine decarboxylase in many tissues is grossly impaired in diabetes and starvation. They also suggest that polyamine formation in vivo is an integral component of the growth-promoting effect of insulin or some factor dependent on insulin.     

Ornithine decarboxylase activity in Helianthus tuberosus

Ornithine decarboxylase (ODC, EC 4.1.1.17) was studied in crude extracts of parenchyma slices of dormant tubers activated for 12 h, tuber shoots and shoot apices. It was highest in shoot apices. The enzyme activity was measured by the production of ¹⁴CO₂ from labelled ornithine; V_max was 450 nmol (mg protein)^-1h^-1, K_m for ornithine and pyridoxal phosphate were, respectively, 30 m M and 5μ M . Only when partially purified, the ¹⁴CO₂ production was inhibited by α-difluoromethylornithine, while in crude extracts dithiothreitol was inhibitory. Ornithine and arginine decarboxylase (ADC, EC 4.1.1.19) activities from parenchyma tubers were not greatly altered by exogenously supplemented ornithine, even though its endogenous pool increased. Exogenously supplemented arginine enhanced ornithine decarboxylase activity, whereas putrescine decreased it slightly. The possibility of artifactual activities in the crude extract is also discussed.     

The influence of androgen status on metabolic activity in the rat epididymis

Forty-two bovine fetal fluid samples (29 by transsacrosciatic amniocentesis, 2 by transischiorectal amniocentesis, 11 from slaughter-house material) were set up in tissue culture. Thirteen cultures failed due to either incubator failure, bacterial or fungal contamination, or the paucity of culturable cells. Sufficient growth for sex chromosome analysis was obtained in 29 smaples. Twenty-four of these were correctly sexed, three could not be verified and two were incorrectly sexed.Contamination of fetal fluid samples with maternal cells was found to be a major problem which could lead to the misinterpretation of results. To minimize this possibility: the first 1–2 ml of aspirated fetal fluids must be discarded; multiple cultures should be initiated from each sample; and when male cells are not observed, numerous metaphase spreads from each culture and from several passages must be analyzed.     

Androgen-dependence of ornithine decarboxylase in the rat epididymis

Ornithine decarboxylase (ODC) activity was measured in epididymides of 45-day-old rats. Higher ODC activity was detected in the corpus and cauda than in the caput epididymidis. Bilateral castration for 7 days caused epididymal ODC to fall to undetectable values, whereas testosterone restored activity to normal values. The effect of the androgen was significantly inhibited by cyproterone acetate. The caput was more sensitive to the action of testosterone than were the corpus and caudal segments. Unilateral castration for 4 or 8 days did not affect ODC on the control or castrated side, but the activity fell in epididymides of both sides after removal of the remaining testis. These results show that epididymal ODC activity is androgen-dependent.     

Ornithine decarboxylase as a tool in developmental neurobiology.

The developmental pattern of ornithine decarboxylase (ODC) activity has proven valuable in elucidating the influence of the perinatal environment on maturation of the central and peripheral nervous systems. Effects of hormones, drugs and maternal-neonatal interactions on ODC can be used to predict subsequent alterations in brain growth, central neurotransmitter systems and ontogeny of sympathetic nerve function.     

Ornithine decarboxylase activity associated with a particulate fraction of brain

The enzymic decarboxylation of ornithine by adult rat brain largely occurs in the particulate fraction. The activity is primarily due to ornithine decarboxylase (ODC) as evidenced by several criteria: i) the concurrent production of equimolar amounts of CO₂ and putrescine, ii) the sensitivity of the reaction to difluoromethylornithine (DFMO), a specific inhibitor of ODC, iii) the lack of major effect of two inhibitors of ornithine-2-oxo-acid transaminase, upon the DFMO-sensitive component of decarboxylation, iv) the failure to profoundly reduce decarboxylation activity in the presence of a large excess of many aminoacids which could compete for non-specific decarboxylases. The insoluble ODC activity appears largely within synaptosomal and mitochondrial-enriched morphological fractions, yet cannot be attributed to trapped soluble ODC. Particulate ODC has a pH optimum and kinetic parameters that differ from those of soluble cerebral ODC.     

Ornithine decarboxylase activity and: [125I]iododeoxyuridine incorporation in rat prostate.

The relationship between ornithine decarboxylase activity and [125I]iododexyuridine incorporation was studied in prostates from castrated rats (aged 5, 26 and 80 weeks) injected daily with testosterone for up to 10 days. The results suggest that ornithine decarboxylase activity is a parameter of secretory activity, rather than growth, in the ventral prostate. In the dorsolateral prostate, ornithine decarboxylase activity tends to parallel [125I]iododeoxyuridine incorporation.     

Ornithine decarboxylase protein diversity and activity modulation in HTC cells

Ornithine decarboxylase of HTC cells was chromatographically separated into three ionically distinct but kinetically similar forms of this protein. The sequential appearance of these ornithine decarboxylase species during enzyme induction, and the accumulation of normally minor species under conditions that stabilize this enzyme, suggest that these represent modifications that are associated with the extremely rapid turnover of this protein $\text{in vivo}$. These forms may also be differentially active or unequally distributed $\text{in vivo}$ as indicated by the selective inactivation of one of the forms by short exposure to α-difluoromethylornithine.     

Ornithine decarboxylase is upregulated by the androgen receptor in skeletal muscle and regulates myoblast proliferation

The aim of this study is to determine if the Odc1 gene, which encodes ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, is directly regulated by the androgen receptor (AR) in skeletal muscle myoblasts and if Odc1 regulates myoblast proliferation and differentiation. We previously showed that expression of Odc1 is decreased in muscle from AR knockout male mice. In this study, we show in vivo that Odc1 expression is also decreased >60% in muscle from male muscle-specific AR knockout mice. In normal muscle homeostasis, Odc1 expression is regulated by age and sex, reflecting testosterone levels, as muscle of adult male mice expresses high levels of Odc1 compared with age-matched females and younger males. In vitro, expression of Odc1 is 10- and 1.5-fold higher in proliferating mouse C(2)C(12) and human skeletal muscle myoblasts, respectively, than in differentiated myotubes. Dihydrotestosterone increases Odc1 levels 2.7- and 1.6-fold in skeletal muscle cell myoblasts after 12 and 24 h of treatment, respectively. Inhibition of ODC activity in C(2)C(12) myoblasts by α-difluoromethylornithine decreases myoblast number by 40% and 66% following 48 and 72 h of treatment, respectively. In contrast, overexpression of Odc1 in C(2)C(12) myoblasts results in a 27% increase in cell number vs. control when cells are grown under differentiation conditions for 96 h. This prolonged proliferation is associated with delayed differentiation, with reduced expression of the differentiation markers myogenin and Myf6 in Odc1-overexpressing cells. In conclusion, androgens act via the AR to upregulate Odc1 in skeletal muscle myoblasts, and Odc1 promotes myoblast proliferation and delays differentiation.     

Ornithine decarboxylase activity in human endometrium and endometrial cancer cells

Summary Ornithine decarboxylase (ODC) activities were significantly higher in proliferative endometrium during the estrogen-dominated follicular phase of the menstrual cycle than in secretory endometrium after the formation of the progesterone-secreting corpus luteum. The enzymatic activity was increased about fivefold by renewal of the medium during incubations of endometrial fragments or isolated endometrial glands. Endometrial adenocarcinoma cells (HEC-1, HEG-50), both in monolayers and suspension, also responded to medium renewal by increasing ODC activity about 10-fold after 4 h, with subsequent reduction to control levels after 7 h. These effects were blocked by actinomycin D and cycloheximide. Endometrial stromal cells exhibited highly variable ODC activities at different passages. Difluoromethylornithine (DFMO) and sodium molybdate had marked antiproliferative effects in HEC-50 cultures, reducing cell numbers to 10 to 20% of control values 11 d after plating and inhibiting ODC activity by approximately 80% on Day 7. The antiproliferative effect of DFMO, but not that of molybdate, was reversed by 10 μM putrescine, the product of ODC activity. In contrast to DFMO, molybdate had no effect on ODC activity of cell homogenates. Molybdate did not elicit antizyme formation in HEC-50 cells under conditions in which putrescine did. These results indicate that ODC activity, present in both epithelial and stromal cells, as shown analytically and also by autoradiography after labeling with [³H]DFMO, may be related to cell proliferation in vivo and that proliferation of human endometrial cancer cells in culture can be arrested by DFMO and by molybdate. This investigation was supported by PHS grant HD 07197, awarded by the National Institute of Child Health and Human Development and PHS grant CA 15648, awarded by the National Cancer Institute.     

Ornithine decarboxylase activity and actin polymerization in testosterone--stimulated mouse kidney

Renal hypertrophy was induced in mice by injection of testosterone. Associated with an increase in renal tissue mass were increases in the concentrations of spermine and spermidine and in the activity of ornithine decarboxylase (ODC), the rate limiting enzyme in their synthesis. The increased activity of ODC was shown to be due to an increase in tissue ODC content. Total tissue actin was not altered by testosterone treatment although the proportion of unpolymerized (soluble) actin was increased significantly. These data are discussed in relation to the postulated mechanism of polyamine stimulation of actin polymerization.