Ornithine decarboxylase is important in intestinal mucosal maturation and recovery from injury in rats

Mucosal polyamine profile in normal and adapting (hypo and hyperplastic) intestine: effects of DFMO treatment

The polyamines, putrescine, spermidine, and spermine, are believed to play an important role in modulating normal and adaptive intestinal mucosal growth. Polyamine synthesis is rate limited by ornithine decarboxylase (ODC) and ODC activity is specifically inhibited by -difluoromethyl ornithine (DFMO). To assess the importance of polyamines in adaptive growth we first measured mucosal polyamine profiles at different sites in the normal rat intestine and compared the results with those obtained in adaptive hypoplasia (seven days parental nutrition, TPN), in the adaptive hyperplasia of two weeks after 90% small bowel resection (SBR) or pancreatico biliary diversion (PBD). We then examined the effects of DFMO (2% in drinking water, daily from two days before surgery) on the polyamine concentrations and the adaptive response to PBD. The hyperplasia of SBR and PBD was associated with increases in all the polyamine concentrations particularly putrescine. TPN induced a modest degree of hypoplasia and little change in polyamine synthesis resulting in subnormal polyamine concentrations and significantly inhibited the mucosal adaptive response. Changes in polyamine metabolism are important in intestinal mucosal adaptation and by controlling these changes adaptive growth can be controlled.

Polyamines in normal and cancer cells

Based on available evidence, it appears that polyamines are critical for proliferation of both normal and transformed cells. Although the requirement of polyamines for DNA replication and cell proliferation is established, the molecular events in which the polyamines are essential are yet unknown. Furthermore, transformed and cancer cells, possibly because of their higher proliferative rate, appear to be more dependent on polyamine metabolism than their normal counterparts. This has been shown by the in vivo response of tumor models and human tumor xenografts in nude mice to polyamine depletion by DFMO. Although there has been associated toxicity to the host, the inhibition of cell proliferation has been higher in the implanted tumors than in the host. DFMO, a specific irreversible inhibitor of ODC, has been used extensively in studies which have shed light on the role of polyamines in cell proliferation and differentiation. DFMO has shown interesting anti-tumor effect in a number of experimental tumor models. Currently, DFMO clinical trials are being completed, and it will be of interest to see whether this polyamine inhibitor, or other newer polyamine analogs and inhibitors, will find a place in the treatment of neoplastic disorders.

Biochemical markers in patients with familial colonic neoplasia

Many potential markers, including biochemical markers, have been studied in an attempt to identify the presence of early colorectal neoplasia or risk of neoplasia, particularly in those families with hereditary colonic neoplasia syndromes. Unfortunately, most of these markers are useless in screening or diagnosis. Nevertheless, such markers as carcinoembryonic antigen (CEA) and CA 19-9 may have a role in pretherapeutic and posttherapeutic monitoring of disease or recurrence. The newer tumor markers, including the carbohydrate markers, ornithine decarboxylase (ODC) and the polyamines, are of great interest as potential tumor markers; ODC and the polyamines may also have a future potential as therapeutic targets. However, further studies are needed to determine their true sensitivity and specificity in hereditary colonic neoplasia syndromes, as well as in patients without genetic syndromes who are at risk for colorectal cancer.

Red blood cell polyamine levels and host toxicity during continuous alpha-difluoromethylornithine infusion

The dose effects of continuous alpha-difluoromethylornithine (DFMO) infusion on red blood cell (RBC) polyamine levels, host toxicity and tumor growth were determined. Male rats with and without a transplantable methylcholanthrene-induced sarcoma received intravenously either 0.45% NaCl or DFMO at 500 mg, 1,000 mg, or 2,000 mg/kg body wt/day for 6 or 12 days. Dose-related inhibition of tumor growth was noted after the 12-day treatment. There were no changes in host carcass weight, food intake, plasma albumin, hematocrit or white blood cell counts. Platelet suppression was associated with the 1,000- and 2,000-mg doses with the 12-day treatment. Morphometry of the small intestine revealed mild but significant shortening of villi in the duodenum and jejunum at the 2,000-mg dose, but none of the animals developed diarrhea. The 500-mg DFMO dose reduced the rate of tumor growth without inducing platelet suppression or altering intestinal morphology. A decrease in RBC putrescine levels was noted at all doses. RBC spermidine levels increased with the 500-mg dose. RBC spermine levels were higher at all doses compared with controls. These results suggest that thrombocytopenia is the major dose-limiting side-effect of continuous DFMO infusion but does not occur at a dose of 500 mg/kg body wt/day.

Essential role of polyamine metabolism in hepatic regeneration. Inhibition of deoxyribonucleic acid and protein synthesis and tissue regeneration by difluoromethylornithine in the rat

We studied liver regeneration after partial hepatectomy and the effects of inhibition of ornithine decarboxylase (ODC) and putrescine administration. The specific ODC inhibitor, alpha-difluoromethylornithine was given as a 3% oral solution (5.4 g/kg X day intake) to hepatectomized rats as well as sham-operated controls. alpha-Difluoromethylornithine had no effect other than inhibition of the low basal levels of ODC in sham-operated rats, but it markedly inhibited increases in ODC by 85% in hepatectomized rats. alpha-Difluoromethylornithine reduced hepatic deoxyribonucleic acid synthesis by 61%, protein synthesis by 46%, and liver weight increased by 83%, showing that alpha-difluoromethylornithine inhibition of ODC inhibits liver regeneration. Putrescine (2 mmol/kg X day) was then given intraperitoneally to hepatectomized rats and controls. Putrescine had no effect in rats not given alpha-difluoromethylornithine. In rats given alpha-difluoromethylornithine, putrescine markedly reversed the inhibitory effect of alpha-difluoromethylornithine on ODC (83%), deoxyribonucleic acid synthesis (94%), protein synthesis (95%), and liver regeneration (85%). These results document that the increases in ODC are important in hepatic regeneration and that polyamine metabolism plays an important role in the increased deoxyribonucleic acid and protein synthesis in this hepatic proliferative response.

Polyamine distribution in the rat intestinal mucosa

As the first step in a study of mucosal polyamine metabolism during intestinal adaptation, we have measured mucosal polyamine concentrations at different sites along the normal rat intestine. Putrescine, spermidine, spermine and cadaverine were measured by spectrofluorometric analysis after thin-layer chromatography of their dansylated derivatives. Spermidine was present in the largest amounts at each of the sampling sites. The ratio of the concentration of spermidine to that of spermine paralleled the established pattern of cellular proliferation in the normal intestine as did the putrescine concentration (nmol per 10 cm) which decreased from duodenum to colon. These results provide the essential background to an assessment of the role of polyamines in the intestinal adaptive response.

Ornithine decarboxylase activity during formation of experimental epiretinal membranes

This study demonstrates in a rabbit model of epiretinal membrane formation that retinal-associated ODC activity increases during this pathological process. These changes in retinal-associated ODC activity most likely occur in relationship to the proliferative lesion itself, since the retina consists primarily of nonproliferative tissues. Further knowledge of intraocular polyamine metabolism during epiretinal membrane formation which can result in retinal detachment may lead to the development of an effective pharmacological treatment.

Marked and prolonged inhibition of mammalian ornithine decarboxylase in vivo by esters of (E)-2-(fluoromethyl)dehydroornithine

(E)-2-(fluoromethyl)dehydroornithine, a new enzyme-activated irreversible inhibitor of ornithine decarboxylase (ODC) is no more effective than alpha-difluoromethylornithine (DFMO) at inhibiting polyamine biosynthesis in rat hepatoma tissue culture (HTC) cells and in rat organs even though its potency is over 15 times higher than that of DFMO in vitro. The methyl, ethyl, octyl and benzyl esters of (E)-2-(fluoromethyl)dehydroornithine were synthesized as potential prodrugs of the amino acid. When tested at concentration equivalent to the Ki value of the amino acid, they are devoid of ODC-inhibitory property. When measured 6 hr after its addition to the HTC cell culture medium, the absorption of methyl ester was 20 times higher than that of the parent amino acid or that of DFMO, and was accompanied by a more marked intracellular accumulation of (E)-2-(fluoromethyl)dehydroornithine than that achieved by the addition of the parent amino acid. The methyl ester used at 10 times lower concentrations is as effective as its parent amino acid or as DFMO at inhibiting polyamine biosynthesis in HTC cells. Similarly, the methyl and the ethyl esters of (E)-2-(fluoromethyl)dehydroornithine used at 10 times lower doses are as effective as the parent amino acid and as DFMO at inhibiting ODC in the ventral prostate of rat, 6 hr after oral administration. All the esters of (E)-2-(fluoromethyl)dehydroornithine produce a particularly long duration of ODC inhibition in the ventral prostate and in the testes. Repeated administration (25 mg/kg given once a day by gavage) of the methyl ester of (E)-2-(fluoromethyl)dehydroornithine for 8 days to rats results in a constant 80% inhibition of ODC over a 24-hr period, accompanied by a 90% decrease of putrescine and spermidine concentrations in the ventral prostate.

Consequences of ornithine decarboxylase inactivation by alpha-difluoromethylornithine and 5-fluorouracil on the growth of rabbit fibroblasts

The role of ornithine decarboxylase and polyamines in proliferative vitreoretinopathy (PVR) is ill-defined. An increase in the activity of this enzyme concurrent with an increase in polyamine levels may be essential in the process of intraocular cellular proliferation. Therefore, in this study, cultured rabbit fibroblasts were exposed to DL-alpha-difluoromethylornithine (alpha-DFMO), a mechanism-based irreversible inactivator of ornithine decarboxylase, alone and in combination with 5-fluorouracil (5-FU). Concentrations of 0.1mM alpha-DFMO and 0.125mM 5-FU decreased rabbit fibroblast cell number by 60% and 65%, respectively, after three days, while with either 5.0mM alpha-DFMO or 0.25mM 5-FU, cell number is decreased by 95%. The effectiveness of inhibitory concentrations of 5-FU and alpha-DFMO together in reducing cell number is additive.

Binding of diamine oxidase activity to rat and guinea pig microvascular endothelial cells. Comparisons with lipoprotein lipase binding

Microvascular endothelial cells from rat and guinea pig fat pads were shown to bind diamine oxidase (DAO) activity when incubated with soluble extracts of placenta (33 DAO U/mg of placenta) and a purified placental enzyme preparation (94 U/micrograms of protein). The extent of binding was dependent on the concentration of enzyme activity and tissue. Saturation of binding sites with 5,000 U of DAO/ml resulted in levels of bound activity (up to 11-13 U/mg of endothelial cells) in excess of that observed in all tissues except placenta. Scatchard plots suggested that there were at least two DAO binding sites (apparent Km 92 and 2,450 U/ml). Although the same cell preparations bound 125I-labeled lipoprotein lipase (LPL), the presence of LPL on the endothelial cell surface did not interfere with the binding of DAO activity except when cells were exposed to high concentrations of LPL. Alternatively, bound DAO activity was partially displaced (up to 33%) only with high concentrations (30 micrograms/ml) of LPL. DAO activity may thus be bound to at least two populations of sites, one of which may bind LPL. Both enzymes, however, were displaced by heparin (0.05-5 U/ml) and DAO binding was impaired by prior treatment of cells with proteolytic and glycosaminoglycandegrading enzymes. The demonstration of DAO binding to vascular endothelial cells provides a further example of the ability of these cells to bind enzymes at their surface and thereby act on biologically active substances in the circulation.

Bacterial lipopolysaccharide induction of ornithine decarboxylase in the macrophage-like cell line RAW264: requirement of an inducible soluble factor

Ornithine decarboxylase (ODC, EC 4.1.1.17) activity is induced in the RAW264 macrophage-like cell line by bacterial lipopolysaccharide (LPS). As little as 0.1 ng/ml LPS promoted an increase in ODC activity, while maximal ODC activity (30-fold above control) was induced with 1.0 microgram/ml LPS. An increase in ODC activity was detectable within 90 min of LPS addition. The LPS-induced increase in ODC activity was prevented by inhibitors of protein and RNA synthesis. The induction of the enzyme by LPS was not dependent on prostaglandin production. However, PGE2 (1 microgram/ml) and 8-bromo-cyclic AMP (1 mM), neither of which had an effect on ODC activity when added alone, each acted synergistically to enhance the LPS induction of ODC activity. Enzyme induction was not associated with an alteration in Km for ornithine, which remained constant at 0.04 mM. The extent of the increase in ODC in response to LPS increased with increasing cellular density. This relationship was dependent not on absolute cell density of the monolayer but on the cell number in relation to medium volume, and this dependence could be extrapolated to the origin. Addition of conditioned media from LPS-stimulated but not unstimulated cultures enhanced the ODC increase in sparsely plated cultures in response to a maximal concentration of LPS. The addition of polymyxin B, a reagent that blocks the effects of LPS, including the increase in ODC activity, did not totally inhibit the conditioned medium stimulation. This data indicates that two signals, LPS and a LPS-induced mediator, are involved in the induction of ODC activity in RAW264 cells.

Hormones and polyamines in intestinal and pancreatic adaptation

The evidence for and against an enteropancreatic trophic axis is reviewed. Luminal nutrition is essential for the maintenance of normal intestinal mucosal, and exocrine pancreatic, structure and function. Exclusion of luminal nutrition leads to mucosal hypoplasia and hypofunction with similar changes in the pancreas. The trophic effect of luminal nutrition may be mediated through the release of regulatory peptides with endocrine or paracrine effects. Enteroglucagon is the strongest candidate for the role of 'enterotrophin' while cholecystokinin (CCK) markedly influences pancreatic growth. Thus, CCK not only stimulates exocrine pancreatic secretion but makes acinar cells divide and the pancreas grow. The cellular mechanisms whereby trophic peptides influence normal and adaptive growth are also discussed with emphasis on polyamines (putrescine, spermidine and spermine) and the key enzymes controlling their synthesis (ornithine decarboxylase; ODC) and degradation (diamine oxidase; DAO). When polyamine synthesis is blocked with the ODC inhibitor, difluoromethyl ornithine (DFMO), the adaptive intestinal hyperplasia of pancreatico-biliary diversion is either inhibited or completely prevented. A proposed sequence of events might be as follows: luminal nutrients, particularly long-chain fats, reach the ileum and colon and stimulate increased enteroglucagon release. Enteroglucagon binds to cell receptors and triggers an intracellular cascade involving ODC and the polyamines, which, in turn, stimulate RNA polymerase, DNA, RNA and protein synthesis, cell division, and adaptive tissue growth.

Analysis of dansyl derivatives of di- and polyamines in mouse brain, human serum and duodenal biopsy specimens by high-performance liquid chromatography on a standard reversed-phase column

The concentrations of putrescine, spermine and spermidine were measured in human serum, children's duodenal biopsy specimens and mouse brain homogenates by high-performance liquid chromatography. The chromatographic analysis was performed on dansyl derivatives of the polyamines using a reverse-phase system with an ion-pairing retention mechanism (heptane sulphonate). Capacity factors were determined at different concentrations of acetonitrile. Simple linear gradients were set up for fast (15 min) or routine (25 min) analysis. Three fluorescence detectors were compared for these determinations and their detection limits determined. The minimum detectable amount of polyamines was 25 fmol compared to 500 fmol with standard detectors. While samples prepared from tissues did not require a high sensitivity, a detector of better performance was needed to assay the polyamines in human serum.

Lipopolysaccharide and serum synergistically stimulate ornithine decarboxylase in Chinese hamster ovary cells

Lipopolysaccharide (LPS), the active component of bacterial endotoxin, caused no significant increase in ornithine decarboxylase (ODC) activity in serum-starved, Chinese hamster ovary fibroblasts. However, concurrent addition of LPS with 10% fetal bovine serum caused a synergistic 30 to 40-fold increase in enzyme activity as compared to the 10 to 20-fold increase seen after addition of serum alone. This synergism was not due to an alteration in the time course of enzyme induction after serum addition. The LPS-induced synergy of ODC induction by serum was inhibited by the concurrent addition of the specific LPS-antagonist, Polymyxin B.

Effects of alpha-difluoromethylornithine on pancreatic growth induced by caerulein

The role of ornithine decarboxylase and of polyamines was investigated on caerulein-induced pancreatic growth by the use of alpha-difluoromethylornithine (DFMO), an enzyme-activated irreversible inhibitor of ornithine decarboxylase. By itself, DFMO did not affect the pancreatic gland at all but when combined with caerulein, it reduced the increases in DNA synthesis and DNA content initiated by the cholecystokinin analog. The general hypertrophic action of caerulein was not affected by DFMO but specific increases in amylase and chymotrypsin concentrations were observed after 2 days of caerulein. The effect on amylase concentration was further increased after 4 days but that on chymotrypsin was reversed, showing a significant decrease. These data suggest that the polyamines might be involved in pancreatic growth that is stimulated by caerulein and that their action could be mainly oriented towards cellularity. The specific decreases obtained in DNA synthesis and content brought about by DFMO support this observation.

Inhibition of intestinal epithelial DNA synthesis and adaptive hyperplasia after jejunectomy in the rat by suppression of polyamine biosynthesis

Transient increases in the activity of ornithine decarboxylase (ODC), the first and rate-limiting enzyme in polyamine biosynthesis, may be critical to initiation of cell growth. We previously reported such increases in ODC activity, and the polyamines, putrescine, and spermidine in rat ileal mucosa between days 1 and 4 after intestinal resection. During this time, there is initiation of mucosal cell hyperplasia, as measured morphologically and biochemically. Intestinal weight and mucosal thickness increase, as do mucosal DNA content and DNA synthesis. In the present study, we gave rats the specific irreversible ODC inhibitor, alpha-difluoromethyl ornithine (DFMO), beginning 3 d before jejunectomy. DFMO completely suppressed the increases in ODC activity and polyamine content in the intestinal mucosa. The suppression in ODC activity was associated with an 87% suppression of DNA synthesis, and resulted in a complete abolition of intestinal adaptation, as manifested by the absence of intestinal weight gain, increase in mucosal thickness, or increase in crypt cell production. Our results indicate that the increases in ODC activity and polyamine biosynthesis are critical for adaptive postresectional crypt cell proliferation in vivo, and that the critical step mediated by polyamines in this adaptive process is the onset of new DNA synthesis.

Ornithine decarboxylase as a biologic marker in familial colonic polyposis

We investigated whether the activity of ornithine decarboxylase might serve as a diagnostic test for detecting the presence of the genotype for familial polyposis. This rate-limiting enzyme in the polyamine biosynthetic pathway is essential for intestinal mucosal proliferation. In colonic mucosa from 16 normal controls, ornithine decarboxylase activity was less than 2.5 nmol per milligram per hour. In contrast, it was higher than 2.5 nmol per milligram per hour in the normal-appearing areas of colonic mucosa from 11 of 13 patients with familial polyposis and in all polyps biopsied from these same subjects (P less than 0.05 for specimens from both sites, as compared with controls). Mucosa from dysplastic polyps showed higher mean ornithine decarboxylase activity than mucosa from polyps that were not dysplastic (P less than 0.05). In colonic mucosa from clinically unaffected, first-degree relatives of patients with familial polyposis, there was a bimodal distribution of ornithine decarboxylase activity, with one peak at the mean for normal controls and the other near the mean for normal-appearing mucosa from affected patients. Our study suggests that ornithine decarboxylase activity in colonic mucosa may reflect the abnormal proliferative state in familial polyposis and identify clinically normal family members who carry the genotype.

Uterine growth responses of the mature castrate rat to estradiol-17B

To examine estrogen-stimulated uterine growth we have monitored changes in uterine DNA synthesis, ornithine decarboxylase (ODC) activity and protein content as well as luminal epithelial (LE) cell mitotic index and ultrastructural changes. We have utilized this model to examine castrate mature rat uterine growth as a function of time between 18 and 40 hours following a single injection of 25.0 ug of estradiol-17B. LE cell mitotic index and protein content increases were maximally elevated as early as 18 hours postinjection while uterine ODC activity was maximal at 28 hours; uterine DNA synthesis increases continued throughout the experiment. In addition, the infusion of either 1 or 2 ug E2 plus progesterone over a 24 hour period, stimulated elevated ODC activity under both treatment regimens and LE cell mitotic index which was inversely related to E2 dose.

Induction of brain ornithine decarboxylase during recovery from metabolic, mechanical, thermal, or chemical injury

Metabolic, mechanical, thermal, and chemical injury induced ornithine decarboxylase (ODC) activity in rat brain. A two- to sixfold increase in ODC activity was measured at 5-9 h after different modes of injury to the brain. During the early phase of recovery from transient ischemia, when average protein synthesis was less than 50% of control, ODC activity was increased nearly fivefold. The rise in activity could be blocked by anisomycin, or reduced by intracerebral injections of actinomycin D. Drilling burr holes into the skull, injection of the vehicle for actinomycin D, hyperthermia, and freezing lesions all caused increased ODC activity. Neurotoxic chemicals (ammonia, methionine sulfoximine, acrylamide, carbon tetrachloride, and anisomycin) also increased brain ODC activity, whereas other chemicals (mannitol and valine) did not. Treatments known to stimulate the synthesis of heat shock proteins (carotid occlusion, hyperthermia, Cd2+, canavanine, and ethanol) induced ODC activity in the liver, whereas only hyperthermia and ethanol caused significant increases in spleen ODC activity. All increases in ODC activity were blocked by difluoromethylornithine, an irreversible inhibitor of ODC. The cellular response to noxious or stressful stimuli includes the synthesis of a small number of proteins of unknown functions; ODC may be one of these "heat shock" or "trauma" proteins.

Rat uterine polyamine biosynthetic decarboxylase activities following multiple injections of estradiol-17 beta and/or estriol

A single injection of 0.5 micrograms estradiol-17 beta (E2) plus 0.5 micrograms estriol (E3) stimulated a different pattern in 22-24 day-old rat uterine ornithine decarboxylase (ODC) and S-adenosyl methionine decarboxylase (SAMDC) activities than was induced by either a single injection of 0.5 micrograms E2 or multiple injections of 0.5 micrograms E3. Differences included alterations in enzyme activity peak timing as well as activity duration. Every 3 hour injections of 0.05 micrograms E2 induced maximum uterine ODC activity at 4, 24, 32, and 40 hours, intermediate activity at 48, 64, and 72 hours as well as a small peak by 56 hours. When 0.05 micrograms E2 plus 0.05 micrograms E3 were injected simultaneously every 3 hours, the ODC activity pattern was similar except that activity fell to intermediate levels by 40 hours. It is suggested that E3 alterations of E2 induced uterine enzyme activities (when monitored at frequent intervals) could be physiological alterations in uterine growth responses due to E2-E3 hormone interactions. However, there appeared to be no differences between E2 or E2 plus E3 induction of DNA synthesis and luminal epithelial cell height and cross-sectional area or ODC and SAMDC activities when measured at 24, 48, or 72 hours.

Polyamine biosynthetic enzymes as targets in cancer chemotherapy

In this chapter we focus attention on recent developments in the biosynthesis of putrescine, spermidine and spermine and their linkage to salvage pathways of methionine and adenine nucleotide synthesis. We describe the use of specific inhibitors of the polyamine biosynthetic enzymes for studying the role of polyamines in cell growth and division as well as in cell differentiation. Some novel findings are presented which suggest that part of the inhibitory action that polyamine synthesis inhibitors exert on DNA synthesis may be due to the accumulation of ADP and ATP. We show that polyamine synthesis inhibitors are capable of inducing terminal differentiation of neoplastic cells to forms with no further proliferative potential, and briefly discuss the potential use of this approach in cancer chemotherapy.

Ileal metabolism in vitro of testosterone to 4-androstene-3 alpha, 17 beta-diol

Testosterone metabolism to 4-androstene-3 alpha, 17 beta-diol by the 800 g supernatant fraction of ileum from male and female rats was investigated. Ileal production of this testosterone metabolite was higher in mature female animals than in mature males. This difference could be eliminated by administration of large doses estradiol-17 beta to mature male rats. Immature animals showed low ileal production of 4-androstene-3 alpha, 17 beta-diol before being weaned from their mother.

Intestinal changes caused by DL-alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase

Subacute (2 week) oral or intravenous administration of DL-alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), caused diarrhea and frequent emesis as early as 4 to 5 days in dogs (dose greater than or equal to 200 mg/kg/day). Diarrhea also occurred in monkeys after 1 week of treatment with an intravenous dose of 1000 mg/kg/day. Especially evident in the treated dogs with diarrhea were fluid loss, hemoconcentration, and decreased serum sodium and chloride which were findings totally reversible about 2 weeks after cessation of dosing. As a result of treatment with the highest intravenous dosage (1000 mg/kg/day), villous atrophy of the mucosa was observed by light and scanning electron microscopy in the canine small intestine. Transmission electron microscopy demonstrated that the most significant alterations of the canine intestinal tract involved the microvilli of epithelial cells which became shorter and were frequently less numerous or absent along focal areas of the plasma membrane. Intestinal mucosal levels of putrescine, especially in the duodenum and jejunum, were decreased as demonstrated in the monkeys following intravenous treatment with 100, 300, or 1000 mg/kg/day of DFMO. The results of this investigation are consistent with the hypothesis that the inhibition of ODC activity and subsequent altered polyamine metabolism may lead to delayed maturation of the intestinal epithelial cells and the impaired development of their microvilli, causing fluid loss due to reduced absorptive surface area.

Polyamine biosynthesis is required for the maintenance of peripheral blood cell elements in the rat

The specific ornithine decarboxylase inhibitor alpha-difluoromethylornithine, when given to adult rats in vivo for 5 wk, resulted in a decrease in peripheral blood cell elements in normal rats and a marked suppression of marrow recovery in rats with chemotherapy-induced marrow hypoplasia. In normal rats, alpha-difluoromethylornithine resulted in a reduction of the leukocyte count to 73% of control, erythrocyte count to 61% of control, and platelet count to 24% of control. The bleeding time was increased to twice normal and 67% of the animals had epistaxis and 42% had melena. In rats treated with the S phase-specific chemotherapeutic agent 1-beta-D-arabinofuranosylcytosine, the simultaneous administration of alpha-difluoromethylornithine prevented the recovery of the bone marrow. The peripheral blood cell counts remained low--leukocyte count was 10% of control, and erythrocyte and platelet counts were 6% of control. All the animals developed epistaxis and melena and there was a 72% mortality. The administration of putrescine (4 mmol/kg, intraperitoneally, daily), the specific polyamine product of ornithine decarboxylase, reversed these hematologic effects in both normal and recovering marrow and resulted in rapid clinical improvement. Thus, the maintenance of normal, adult rat hematologic parameters, as with the proliferation of neoplastic and transformed cells in culture, is critically dependent on continued polyamine biosynthesis.

Altered androgen regulation of differentiated ventral prostate function during aging of the AXC rat

We have examined testosterone regulation of differentiated androgen responsive ventral prostate function in aging AXC rats as a possible means of identifying age-related changes in prostate gene function. Concerning cellular content of functional macromolecules, we identified three categories of age-related change in ventral prostate: (1) diminutions completely reversible by short-term chronic testosterone treatment, as exemplified by androgen receptor content; (2) diminutions partially reversible by testosterone treatment, as exemplified by prolactin receptor content and L-ornithine-decarboxylase (ODC) activity; and (3) diminutions not reversed by exogenous testosterone treatment, as exemplified by S-adenosyl-L-methionine decarboxylase (AMDC) activity. A fourth category of alteration revealed apparent age-related changes in polyamine homeostasis. The anabolic products of ODC and AMDC activities, putrescine, spermidine and spermine, showed an age-related diminished dependence between the activities of ODC and AMDC and ventral prostate polyamine content. The possibility that these changes reflect age-related alterations in ventral prostate gene activity is under investigation.

Metabolism in vitro of testosterone (T) to 17 beta-hydroxy-5 alpha-androstane-3-one (DHT) and 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha) by the 800 g supernatant fraction of ileum from rats

The 800 g supernatant fraction of ileum from rats was incubated with testosterone and production of 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha,17 beta-diol measured. No difference in this production could be determined between ileum from mature female and mature male animals. Ileum from immature rats staying with their mothers from day 12 to day 21 showed increased 5 alpha-reduction of testosterone on days 15, 17 and 21. Ileal metabolism to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha,17 beta-diol was increased in immature animals on day 25 of extrauterine life when consuming rat chow and water ad libitum from day 21. This increase could not be demonstrated on day 28. Immature and mature animals treated either with long-acting ACTH or dexamethasone showed increased ileal conversion of testosterone to the two 5 alpha-reduced metabolites determined. Ileum from mature male rats injected, subcutaneously, with arabinosylcytosine every 8th h for 2 days exhibited increased metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha,17 beta-diol from the 1st to the 6th day after the last injection of arabinosylcytosine. Different aspects of intestinal metabolism of testosterone are discussed.

Diamine oxidase in the hen

In adult hens diamine oxidase (histaminase) activity was found in gastrointestinal tract (with the highest value in ileum), liver and spleen. Intestinal diamine oxidase is predominantly a particle-bound enzyme. In the intestine oxidation of putrescine leads to delta 1-pyrroline formation, in liver both delta 1-pyrroline and gamma-aminobutyric acid are formed. The inhibitor properties of hen intestinal and rat intestinal diamine oxidases are very similar and differ from pea seedling diamine oxidase. The natural dipeptides carnosine and anserine are relatively potent inhibitors of hen intestinal diamine oxidase.

Effects of epidermal growth factor (EGF) on adult mouse small intestine in vivo and in organ culture

1. Exogenous administration of epidermal growth factor (EGF) has not modified the protein and DNA content, nor several brush border enzymes activities of duodenum, jejunum and ileum of intact and fasted adult mice. 2. Exogenous administration of EGF has not stimulated the DNA synthesis in the three regions of the small intestine of intact adult mice. 3. EGF has a stimulatory effect on DNA synthesis of fasted mice intestine 12 hr after injection. 4. In organ culture, EGF has not altered at any concentration (10, 50, 100, 200, 800 ng/ml), the same parameters in duodenal and jejunal explants taken from animals fasted 24 hr before being killed. 5. These last results suggest that the increase of DNA synthesis observed in vivo was not a direct effect of EGF administration. 6. Finally, the EGF content of serum af adult male mice was measured in fed and fasted mice and in the organ culture media.

The in vivo effects of a polyamine analogue on tissue stem cell proliferation

We have studied by autoradiography the effects of 1,3-diaminopropane (DAP) upon cellular proliferation in a number of tissues in vivo in the rat. DAP is a structural analogue of the naturally occurring polyamine putrescine, and is believed to block cellular polyamine synthesis by supressing the induction of ornithine decarboxylase (the rate-limiting enzyme for polyamine biosynthesis). The continuous infusion of DAP into rats that had been partially hepatectomised prevented the subsequent waves of spermidine and DNA synthesis from taking place in the regenerating liver. The inhibition of DNA synthesis is accounted for primarily by a block in the entry of hepatocytes into S phase and not by a reduction in the rate of DNA synthesis itself. In contrast to the regenerating liver, DAP exerted minimal effects upon the proliferation of the gut epithelium and bone marrow elements. The proliferation of stem cells of these latter tissues, which are normally in a state of rapid and continuous proliferation unlike the liver, is thus much more resistant to perturbations in polyamine biosynthesis and function. DAP is consequently unable to arrest and so protect normal rapidly proliferating tissues from damage caused by anti-cancer drugs (e.g. hydroxyurea) that kill only proliferating cells. DAP cannot therefore be employed to selectively protect normal cells but not tumour cells from cytotoxic damage according to a principle we have previously established in tissue culture.

Experimental fecal transmission of human cryptosporidia to pigs, and attempted treatment with an ornithine decarboxylase inhibitor

Fecal material collected from an immunologically deficient man with persistent cryptosporidia infection was stored in potassium dichromate for two weeks and then fed (inoculated) to newborn pigs. The six inoculated newborn pigs shed the organism in their feces starting four to five days afer inoculation and continuing for as long as 22 days after inoculation. Pigs which were killed and necropsied while shedding had cryptosporidia infection of ileum, cecum, and colon. Infected pigs had atrophied ileal villi and flattened irregular cecal and colonic epithelium. Uninoculated littermate controls remained free to the infection and had histologically normal intestinal tracts at necropsy. Treatment of three of the six inoculated pigs with the ornithine decarboxylase inhibitor, DL-alpha-difluoromethylornithine, orally for ten days had no apparent effect on the infection.

alpha-Difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase, inhibits tumor promoter-induced polyamine accumulation and carcinogenesis in mouse skin

The role of ornithine decarboxylase (OrnDCase, EC 4.1.1.17) and of the polyamines [putrescine (Put), spermidine (Spd), and spermine (Spm)] in mouse skin tumor promotion was investigated by the use of alpha-difluoromethylornithine (CHF2-Orn), an enzyme-activated irreversible inhibitor of OrnDCase. 12-O-Tetradecanoylphorbol 13-acetate (TPA), mezerein, and ethyl phenylpropiolate (EPP) were employed as complete, stage II specific, and nonpromoting agents, respectively. TPA and mezerein, but not EPP, provided for a dose-dependent increase in tissue Put accumulation. The Put level in papillomas developed by TPA (2 micrograms) treatment was approximately equal to 15-fold higher than that of the surrounding skin tissue; Spd accumulation was 2- to 3-fold greater in the papillomas. Put administered (intraperitoneally) with TPA greatly enhanced papilloma yield. CHF2-Orn, given orally or intraperitoneally, abolished the TPA-induced OrnDCase activity and Put accumulation in mouse epidermis. The reduction of polyamine accumulation by CHF2-Orn was directly proportional to reduction of tumor size. CHF2-Orn administered in a two-stage (TPA-mezerein) promotion protocol [Slaga, T. J., Fischer, S. M., Nelson, K. G. & Gleason, G. L. (1980) Proc. Natl. Acad. Sci. USA 77, 3659-3663; Slaga, T. J., Klein-Szanto, A. J. P., Fischer, S. M., Weeks, C. E., Nelson, K. & Major, S. (1980) Proc. Natl. Acad. Sci. USA 77, 2251-2254] reduced tumor size, inhibited by 65-70% the number of papillomas per mouse, and decreased by 40% the percentage of mice with tumors when given with the stage II agent mezerein. CHF2-Orn provided considerably less effect on tumorigenesis when administered with the TPA portion of the protocol, and CHF2-Orn did not inhibit the induction of dark basal keratinocytes by TPA. Based on our results with CHF2-Orn, we suggest that regulation of polyamine biosynthesis, particularly Put, is a critical factor in stage II promotion.

In vitro metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol by the rat intestine

The metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol by the 800 g supernatant fraction by different parts of the gastrointestinal tract from male rats was investigated. This metabolism tended to be higher in immature than in mature animals. Administration of dexamethasone or long-acting ACTH to immature and mature rats increased testosterone metabolism to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol by ileum tissue. No such effect could be observed following administration of progesterone, estradiol, prolactin, LH or FSH in mature animals. Development of the gastrointestinal tract from the immature to the mature stage was associated with augmented metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol in the ileum.

Effects of DL-alpha-difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase, on the rat mammary tumour induced by 7,12-dimethylbenz[a]anthracene

1. The effects of DL-alpha-difluoromethylornithine (RMI 71782; DFMO) on the tumours induced in female rats by a single oral administration of 20 mg 7,12-dimethyl-benz[a]anthracene (DMBA) have been investigated. 2. Treatment with DFMO (2% aqueous solution as sole drinking fluid) starting 30 days after administration of DMBA resulted in markedly fewer animals with tumours and greater than 90% reduction in the total number of tumours. 3. In rats bearing at least one palpable tumour, treatment with DFMO (2% in the drinking water) slowed significantly the rate of appearance of new tumours but affected to only a minimal extent the growth of existing tumours. Tumour ornithine decarboxylase activities and putrescine concentrations were reduced by treatment with DFMO; the activity of S-adenosyl-L-methionine decarboxylase was increased and the concentration of spermine either remained unchanged or increased depending on the length of treatment. 4. Cyclophosphamide, 100 mg/kg, injected once then repeated after 10 days, altered neither the rate of appearance of new tumours nor the growth of the existing tumours. Combined treatment with DFMO plus cyclophosphamide resulted in regression of the majority of tumours existing at the start of treatment and a marked reduction in the rate of appearance of new tumours. 5. In conclusion, DFMO has clear antitumoral activity against the rat mammary tumour induced by DMBA. The effects are manifested principally as a decreased rate of tumour appearance but meaningful effects on tumour growth are observed if the drug is administered during early tumour development or in combination with cyclophosphamide.

Cell differentiation and L-ornithine decarboxylase activity in the small intestine of rats fed low and high protein diets

L-Ornithine decarboxylase activity is higher in enterocytes from rats fed low protein rather than high protein diets. Intestinal cell proliferation rate is 50% higher in rats fed high protein than low protein diets. This is not consistent with a direct role of ornithine decarboxylase in intestinal proliferation. It is shown that ornithine decarboxylase is preferentially associated with differentiating villus cells in intestine from rats fed low protein diets.

Dissociation of enhanced ornithine decarboxylase activity and optic nerve regeneration in goldfish

The significance of a previously observed increase in retinal ornithine decarboxylase (ODC, EC 4.1.1.17) following optic nerve crush was investigated in goldfish using a specific irreversible inhibitor of ODC, alpha-difluoromethylornithine (DFMO). Retinal ODC activity and putrescine levels were reduced 80% and 40%, respectively, by intraperitoneal injection(s) of DFMO. In fish in which the right optic nerve was crushed and DFMO was injected at the time of crush, at 2 days and at 4 days later, retinal ODC levels were maximally decreased after the third injection and returned to normal levels by 14 days post-crush (PC). Retinal tubulin synthesis was examined at 10 days PC. No difference in the post-crush/normal ratio of tubulin synthesis was observed between saline-injected and DFMO-injected groups. Neuritic extension was also examined in retinal explant cultures from 11-day PC retina. The neuritic growth index of DFMO-treated retinas did not differ from that of control retinas. Behavioral studies revealed no difference in the rate of recovery of vision between the two groups. Similar results were obtained in experiments using fish maintained in a 0.1% DFMO solution. These results suggest that the increase in retinal ODC associated with nerve crush does not play a causal role in restoration of function.

Ornithine decarboxylase: essential in proliferation but not differentiation of human promyelocytic leukemia cells

The ornithine decarboxylase inhibitor DL-alpha-difluoromethyl ornithine inhibited a proliferation-associated increase in ornithine decarboxylase activity in cultured human promyelocytic leukemia cells, resulting in a marked suppression of cell proliferation and subsequent cell loss. It also inhibited increases in ornithine decarboxylase activity associated with the phorbol ester-induced conversion of promyelocytic HL-60 cells to monocyte-like cells and the retinoic acid-induced conversion to granulocyte-like cells. However, the inhibition of ornithine decarboxylase activity did not prevent cellular differentiation. These results suggest that polyamine biosynthesis has a specific role in cell proliferation rather than in inducing differentiation that is not accompanied by proliferation. The data also demonstrate that cessation of proliferation in HL-60 cells is not necessarily associated with differentiation.

Effect of alpha-difluoromethylornithine on polyamine and DNA synthesis in regenerating rat liver: reversal of inhibition of DNA synthesis by putrescine

The possibility that alpha-difluoromethylornithine, a specific, irreversible inhibitor of ornithine decarboxylase could be used to prevent the rise in hepatic putrescine and spermidine content following partial hepatectomy was tested. Administration of alpha-difluoromethylornithine at a dose of 400 mg/kg every 4 h reduced hepatic putrescine to less than 2 nmol/g, but had only a small effect on the rise in spermidine seen at 28 h after partial hepatectomy. Such treatment also reduced the rise in DNA synthesis produced by partial hepatectomy by up to 70%. The inhibitory effect towards DNA synthesis could be reversed by administration of putrescine which increased the hepatic putrescine content to about 30-40% of that in the regenerating control livers. these results suggest that accumulation of putrescine rather than spermidine is needed for DNA synthesis after partial hepatectomy. They also suggest that part, but not all of the rise in putrescine normally seen in the liver after partial hepatectomy is needed for the enhanced DNA synthesis associated with liver regeneration. Experiments with lower doses of alpha-difluoromethylornithine showed that a substantial part of the rise in hepatic ornithine decarboxylase activity could be abolished without affecting either the rise in spermidine content or the increase in DNA synthesis after partial hepatectomy.

Maturation of growth hormone stimulation of kidney ornithine decarboxylase in the rat

The effect of ovine growth hormone (GH) on kidney ornithine decarboxylase (ODC) was studied in newborn, preweanling and young adult rats. Basal kidney ODC activity was very low from 4 to 22 days after birth but rose 20-fold by day 25; it remained elevated through day 45. GH failed to stimulate ODC in the first two weeks after birth. GH did however stimulate ODC markedly from 20 through 45 days. Kidney ODC was stimulated in the neonate by vasopressin and by isoproterenol, but not by angiotensin II. Liver ODC remained relatively low and stable during development, and was responsive to GH at all ages studied. We conclude that a) the pattern of development of basal kidney ODC appears to be unique to this tissue and may be related to the postnatal maturation of renal morphology and/or function, b) neonatal kidney ODC is unresponsive to certain hormones but is not completely refractory to stimulation. These findings may have implications for the role of hormones in the maturation of the kidney and in the regulation of early renal function.

Difluoromethylornithine irreversibly inactivates ornithine decarboxylase of Pseudomonas aeruginosa, but does not inhibit the enzymes of Escherichia coli

DL-alpha-Difluoromethylornithine, an enzyme-activated irreversible inhibitor of eukaryotic ornithine decarboxylase and consequently of putrescine biosynthesis, inhibited ornithine decarboxylase in enzyme extracts from Pseudomonas aeruginosa in a time-dependent manner t1/2 1 min, and also effectively blocked the enzyme activity in situ in the cell. Difluoromethylornithine, however, had no effect on the activity of ornithine decarboxylase assayed in enzyme extracts from either Escherichia coli or Klebsiella pneumoniae. However, the presence of the inhibitor in cell cultures did partially lower ornithine decarboxylase activity intracellularly in E. coli. Any decrease in the intracellular ornithine decarboxylase activity observed in E. coli and Pseudomonas was accompanied by a concomitant increase in arginine decarboxylase activity, arguing for a co-ordinated control of putrescine biosynthesis in these cells.

Polyamines are necessary for the survival of human small-cell lung carcinoma in culture

Many human small-cell lung carcinoma culture lines grow as multicellular aggregate spheroids, for which high L-dopa decarboxylase activity is a marker. During the initial cell aggregation and the exponential growth phase, there is a marked increase in ornithine decarboxylase activity and an accumulation of polyamines. alpha-Difluoromethylornithine, a specific enzyme-activated, irreversible ornithine decarboxylase inhibitor, blocks the increase in ornithine decarboxylase activity and in polyamines and inhibits human small-cell lung carcinoma cell growth. After the onset of a decreased proliferation rate, the multicellular spheroid aggregates become poorly formed, cell loss ensues, and there is a decrease in L-dopa decarboxylase activity. These findings support the hypothesis that ornithine decarboxylase and the polyamines play an essential role not only in the proliferative phase but also in the viability of human small-cell lung carcinoma cells in culture. The results suggest that alpha-difluoromethylornithine, a virtually nontoxic compound, may be potentially useful in the therapy of this human tumor.

Effects of nicotinamide on NAD and poly(ADP-ribose) metabolism in DNA-damaged human lymphocytes

The effect of nicotinamide on unscheduled DNA synthesis was studied in resting human lymphocytes. In cells treated with UV irradiation or with MNNG, nicotinamide caused a two-fold stimulation of unscheduled DNA synthesis and retarded the rate of NAD+ lowering caused by these treatments. Nicotinamide also reduced the burst of poly(ADP-ribose) synthesis caused by MNNG treatment. Thus under conditions that it enhances unscheduled DNA synthesis, nicotinamide causes marked effects on the metabolism of NAD+ and poly(ADP-ribose). The effect of nicotinamide on unscheduled DNA synthesis was shown to be independent of protein or polyamine synthesis.