Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.1.1.17 (ornithine decarboxylase)
6,351 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of cAMP as a mediator of gonadotropin stimulation of ovarian ornithine decarboxylase (ODC) activity was studied in granulosa cells isolated from small (1--2 mm) porcine ovarian follicles. These cells responded to both FSH and LH with significant increases in intracellular concentration of cAMP. At concentrations of gonadotropins which were saturating for the induction of ODC activity, FSH was a more potent stimulator of both cAMP production and ODC activity than LH. N,O'-Dibutyryl cAMP (1.0--10.0 mM) caused a dose-dependent stimulation of ODC activity which equaled the maximal effect of LH but was significantly less effective than the saturating dose of FSH. 8-Bromo-cAMP was more potent than N,O'-dibutyryl cAMP and as effective as FSH as an inducer of ODC activity. Addition of theophylline, a phosphodiesterase inhibitor, to the incubation medium resulted in a dose-dependent inhibition of ODC activity in both control and gonadotropin-stimulated cells. In contrast, 1-methyl,3-isobutyl xanthine, another phosphodiesterase inhibitor, potentiated effects of both submaximal and maximal effective doses of gonadotropins while producing no effect on basal ODC activity of these cells. The results of this study are consistent with the concept that cAMP can mediate gonadotropin stimulation of ODC in porcine granulosa cells. In addition, this study shows the importance of proper selection of cAMP analogs and phosphodiesterase inhibitors, and their concentration in studying such effects.
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PMID:Gonadotropin stimulation of porcine ovarian ornithine decarboxylase in vitro: the role of 3',5'-adenosine monophosphate. 8 47

The regulation of the activity of the renal enzyme ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) was examined in the rat. In the intact animal adapted to a light/dark cycle of 14 hours and 10 hours, respectively, the level of renal ornithine decarboxylase activity was rhythmical and paralleled the diurnal rhythm in plasma corticosteroid concentration. Renal ornithine decarboxylase activity and plasma corticosterone were highest during the early hours of darkness and lowest during the hours of light. Following hypophysectomy, the level of renal ornithine decarboxylase activity declined rapidly and remained low and without a demonstrable diurnal rhythm. When pituitary hormone levels were temporarily restored in the hypophysectomized rat by the injection of pituitary extract, renal ornithine decarboxylase activity increased rapidly, reached a peak within 8 hours, and returned toward pre-injection levels by 12 hours. Exogenous growth hormone, ACTH and cortisol each increased renal ornithine decarboxylase activity in the hypophysectomized rat, with the highest levels of activity being achieved with growth hormone. Other pituitary hormones (FSH, LH, TSH and prolactin) were ineffective. After bilateral adrenalectomy, renal ornithine decarboxylase activity retained a rhythmical pattern similar to that observed in the intact rat, but the levels were increased. Growth hormone and cortisol increased renal ornitine decarboxylase activity in the adrenalectomized-hypophysectomized animal to the same extent as in the hypophysectomized animal, but ACTH was almost totally ineffective. These data suggest that the pituitary plays a major role in the regulation of renal ornithine decarboxylase activity in the rat, primarily through the rhythmical secretion of growth hormone and ACTH.
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PMID:Hormonal regulation of renal ornithine decarboxylase activity in the rat. 17 86

Pregnant mare serum gonadotrophin given intravenously to immature rats caused a maximal (x 70) increase in ornithine decarboxylase activity (ODC) at 3 h; enzyme activity declined to about ten times the control levels by 9 h and a second rise began after about 20 h. Anti-PMSG given 30 min after PMSG reduced the peak response by 70%. Actinomycin D, or cycloheximide, completely prevented an increase in ODC when given with PMSG, but only cycloheximide lowered the enzyme activity when given 18 h later. Ovine FSH plus LH also produced a peak in ODC at 3 h but the activity decreased quickly and by 9 h it was at the control level. Secretion of endogenous FSH and LH, induced by hourly injections of LH releasing hormone (LH-RH) increased ODC to the same extent as did the exogenous hormones; ODC was still higher than in the controls 4 h after the last dose of LH-RH. Increased endogenous levels of FSH and LH did not consistently raise ovarian cyclic AMP content and the increases found were much less than those obtained after injection of PMSG or FSH+LH. The results indicate that increased ODC is induced and maintained by the continual presence of gonadotrophin. The dependence of increased ODC upon increased cyclic AMP cannot be unequivocally determined because of important differences in the timing of the responses and the difficulty in determining biologically significant changes in cyclic AMP.
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PMID:Temporal changes in ovarian ornithine decarboxylase and cyclic AMP in immature rats stimulated by exogenous or endogenous gonadotrophins. 19 94

Under defined conditions in vitro FSH and LH caused a dose-dependent stimulation of ornithine decarboxylase (ODC) activity in granulosa cells isolated from porcine ovarian follicles. In cells from small follicles, FSH was at least twice as potent an inducer of the enzyme activity as LH. The cells from medium-sized follicles were more responsive to both hormones than cells from small follicles. In addition, the cells from medium-sized follicles were approximately equally responsive to maximal FSH and LH stimulation. Incubation of cells from either small follicles or medium-sized follicles with maximum effective doses of LH plus FSH caused no additive effects.
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PMID:FSH and LH stimulation of ornithine decarboxylase activity: studies with porcine granulosa cells in vitro. 56 91

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.
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PMID:Effect of follicle-stimulating hormone and its antiserum on the activity of ornithine decarboxylase in the ovary of rat and hamster. 57 30

Prolactin (PRL) has been shown to exert many different actions in various biological systems. Polyamines are known to influence the growth and function of the seminal vesicles (SV). Furthermore, ornithine decarboxylase (ODC) is considered a key enzyme in the biosynthesis of polyamines and is regulated by PRL in certain target tissues. Adult Ames dwarf mice (df/df), genetically deficient in PRL, were used for this study. The experimental groups were as follows: Group 1, pituitary-grafted; Group 2, sham-operated; Group 3, castrated + testosterone propionate (TP)-treated (25 micrograms/mouse, 3 times/wk, s.c.) + grafted; and Group 4, castrated + TP as above. The animals were killed 40 days later, and polyamines and ODC activity in SV and liver were determined. Serum PRL, FSH, and testosterone (T) were also measured. In the grafted groups, there were significant elevations in serum PRL and FSH levels. In the gonad-intact, pituitary-grafted group, animals exhibited an elevation in plasma T levels, and similar levels were achieved in the castrated, androgen-replaced groups. In hyperprolactinemic mice, the weights of SV were significantly greater than in the corresponding control groups. The relative weights of the SV showed a similar pattern. An increase in ODC activity was observed in both SV and liver in hyperprolactinemic groups. In those animals in which serum T levels were held constant, an increase in the enzyme activity in SV was detected in hyperprolactinemic group whereas in liver, no significant difference was observed. Concentrations of polyamines in the SV were increased in hyperprolactinemic, castrated, TP-treated mice. The present results indicate that PRL can exert a direct stimulatory effect on the growth, ODC activity, and polyamine levels in the SV.
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PMID:Effects of hyperprolactinemia on ornithine decarboxylase activity and polyamine levels in seminal vesicles of genetically prolactin-deficient adult dwarf mice. 200 32

The effect of follicle stimulating hormone on the activity of ornithine decarboxylase (ODC) was determined in primary culture of rat Sertoli cells. Three different FSH preparations (NIH oFSH-S-15, S-16, and eFSH) inhibited ODC activity in rat Sertoli cells under different media conditions. The inhibition was both time- and dose-dependent. The mechanism of the FSH inhibitory effect was studied using dibutyryl cyclic adenosine monophosphate (dbcAMP), 1-methyl-3-isobutylxanthine (MIX), forskolin, and isoproterenol. All of these agents, known to elevate cellular cAMP levels, inhibited ODC activity in cultured rat Sertoli cells. The combined effect of each of these substances plus FSH was either greater than, or equal to, that of FSH alone, and was not additive. Dibutyryl cyclic guanosine monophosphate had no effect on the ODC activity. These findings suggest that FSH inhibition of ODC activity in the rat Sertoli cell may be mediated by cAMP.
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PMID:Inhibition of ornithine decarboxylase activity by follicle stimulating hormone in primary culture of rat Sertoli cells. 244 78

In our colony of female rats (220-320 g body weight) undergoing regular 4-day oestrous cycles there were significant, marked rises in concentrations of LH, FSH and prolactin between 09.00 and 19.00 h on pro-oestrus. The i.p. injection of difluoromethylornithine (DFMO; 40-400 mg/kg), a specific inhibitor of the activity of ornithine decarboxylase, at 15.00 h on pro-oestrus had a differential effect on the rise in plasma concentrations of the various hormones thereafter. The drug produced a significant, partial, dose-related suppression of the rise in plasma concentrations of LH and prolactin, but had no significant effect on the rise in FSH. For time-course studies, 120 mg DFMO/kg were injected at 13.00, 15.00 or 17.00 h and groups of animals killed at 19.00 h. Only the injection at 15.00 h was effective in causing a significant reduction in plasma concentrations of LH and prolactin at 19.00 h. Pituitary content of the hormones was found to be unaffected by the administration of DFMO at the times and doses tested. These results suggest that DFMO has a selective inhibitory effect on enhanced LH and prolactin secretion on the afternoon of pro-oestrus in the rat, whilst not affecting FSH release. There seems to be a limited time (after 13.00 but before 17.00 h) during which its administration is effective.
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PMID:Differential effect of difluoromethylornithine on the increases in plasma concentrations of reproductive hormones on the afternoon of pro-oestrus in the rat. 250 98

The effect of testosterone on the induction of Sertoli cell ornithine decarboxylase (ODC) activity was investigated in highly purified cultures derived from testes of 20-day-old rats. Sertoli cell cultures were maintained in serum-free Ham's F-10 medium, with refeeding on days 2 and 4. Before refeeding on day 4, ODC activity was 7.4 U (1 U = 1 pmol 14CO2 released/mg protein.60 min at 37 C). After a medium change, ODC activity increased (41.6 U at 10 h; 180.0 U at 24 h) and then returned to near-basal activity (26.3 U) after 48 h. Simultaneous addition of testosterone (150 ng/ml; 5.2 X 10(-7) M) with the day 4 medium change suppressed the increase in ODC induction (7.53 U at 10 h, 91.6 U at 24 h). Addition of testosterone 24 h before refeeding resulted in greater inhibition of ODC induction (6.9 U at 10 h; 45.4 U at 24 h) than when added simultaneously. Other androgens, 5 alpha-dihydrotestosterone, androsterone, and 5 alpha-androstane-3 alpha,17 beta-diol, also suppressed induction of ODC, whereas 17 beta-estradiol was ineffective, illustrating the steroid specificity of the effect. Coadministration of the antiandrogens hydroxyflutamide or cyproterone acetate partially blocked the testosterone effect. Induction of ODC activity by ovine FSH (10 ng/ml) was also suppressed when Sertoli cells were cultured in the presence of testosterone (150 ng/ml) from the time of isolation. However, induction of ODC activity by (BU)2cAMP was uncompromised by testosterone. These results suggest that testosterone may repress ODC activity and, hence, polyamine biosynthesis in the Sertoli cell, but that cAMP, acting through the trophic hormone FSH, can overcome this suppression of putrescine biosynthesis. Intratesticular and hypophyseal modulation of polyamine biosynthesis may influence not only cellular processes in the Sertoli cell itself but also its role in spermatogenesis.
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PMID:Testosterone suppression of ornithine decarboxylase activity in rat Sertoli cells. 284 Feb 65

Sertoli cells derived from 21-day-old rats were cultured in serum-free Ham's F-10 medium to allow a direct investigation of the effects of FSH on polyamine (PA) biosynthesis in a defined culture system. After 48 h in culture, the basal cellular content consisted predominantly of spermine (1.1 nmol/mg protein) with substantially lower amounts of spermidine (0.1 nmol/mg protein) and undetectable amounts of putrescine. Upon the addition of ovine FSH (3 X 10(-9) M), cellular spermine content became significantly elevated above the control value as early as 1 h after treatment, reaching a 2.5-fold stimulation by 4 h. Spermidine was also elevated by 4 h after FSH treatment, but remained less than 20% of the spermine concentration. At no time did the cellular content of putrescine increase to measurable levels. Extended time-course studies demonstrated that the FSH-induced cellular increase in spermine and spermidine content persisted up to 24 h during the continuous presence of FSH. Bu2cAMP (5 mM) invoked similar changes in PA levels when measured at 4, 8, and 24 h. Ornithine decarboxylase (ODC) activity, which catalyzes the production of putrescine, was increased by FSH in a temporal fashion similar to that of spermine production. Addition of alpha-difluoromethylornithine, an irreversible inhibitor of ODC, blocked increases in both ODC activity and PA in cells stimulated with FSH or Bu2cAMP. Pulse-chase experiments using [3H]ornithine demonstrate that putrescine is initially synthesized, and is subsequently converted to spermidine and spermine. These studies suggest that regulation of PA biosynthesis by FSH is largely expressed as increases in spermine, and to a lesser extent spermidine, suggesting that the more complex PAs may be involved in the regulation of Sertoli cell function.
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PMID:Stimulation of polyamine biosynthesis by follicle-stimulating hormone in serum-free cultures of rat Sertoli cells. 302 35


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