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Biomedical subjects

E A Duell

Publications and source records attributed to E A Duell.

At least 19 recordsLinked to original sources
PubMed1992

Arachidonic acid metabolites: effects on inflammation of fetal rabbit excisional wounds.

Uncovered fetal rabbit excisional wounds do not exhibit any classic signs of healing; wounds covered with an impermeable cover do contract, reepithelialize, and exhibit inflammation. Prostaglandin E2 (PGE2) is elevated in amniotic fluid, acting as an immunosuppressant at the maternal-fetal interface. Full-thickness excisional wounds were made on 25-day gestational age rabbit fetuses. Half the wounds were covered with an impermeable cover. Tissue from covered, uncovered, and nonwounded fetuses was examined 72 h after wounding for arachidonic acid metabolites. Uncovered wounds had significantly (P less than or equal to 0.05) elevated levels of PGE2, PGF2 alpha, and 12-HETE versus covered wounds and control tissue. Covered wounds had significantly elevated levels of 15-HETE compared to uncovered and control tissue. The elevated PGE2 in uncovered wounds may act as a fetal immunosuppressant; covered wounds (lower PGE2) developed cellular inflammation. Further investigations of these interactions may permit modulation of adult inflammation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1992

Cyclosporine metabolism by P450IIIA in rat enterocytes--another determinant of oral bioavailability?

Cyclosporine is converted to its major metabolites (M-17, M-1, and M-21) in human liver by enzymes belonging to the P450IIIA subfamily. These enzymes are also present in rat and human enterocytes; however, the possibility that CsA is metabolized in enterocytes has not been previously investigated. We therefore directly compared metabolism of 3H-CsA in microsomes prepared from liver and jejunal enterocytes. M-17, M-1, and M-21 were the major CsA metabolites produced by enterocyte microsomes. This metabolism appeared to be catalyzed by P450IIIA, because pretreatment of rats with the P450IIIA inducer dexamethasone significantly increased the rate of CsA metabolism in enterocyte microsomes and preincubation of enterocyte microsomes with anti-P450IIIA IgG inhibited the production of CsA metabolites by greater than 95%. To determine if enterocyte P450IIIA metabolizes CsA in vivo, rats were pretreated with the P450IIIA inducer dexamethasone, the P450IIIA inhibitor erythromycin, or vehicle alone. At laparotomy, 2 mg/kg of 3H-CsA was injected into a sealed loop of jejunum, and after collection of the mesenteric venous blood draining this segment for 45 min, the production of M-17 and M-1 was measured. In the control group, a mean of 3.9% of the recovered radioactivity was found as M-1 and M-17. In the rats pretreated with dexamethasone, a mean of 8.4% of the radioactivity was found as M-1 and M-17 (P less than 0.05 relative to control) and this decreased to 2.3% in the group pretreated with erythromycin (P = 0.08 relative to control). We conclude that P450IIIA in jejunal enterocytes readily metabolizes CsA. Furthermore, the metabolism of CsA by enterocytes in vivo is substantial and likely contributes to "first pass metabolism" of orally administered CsA. Our observations provide novel hypotheses to explain some important drug interactions and interpatient differences in CsA dosing requirements.

Administration, Oral↗
PubMed1992

In vitro model of essential fatty acid deficiency.

The polyunsaturated fatty acids linoleic acid (18:2, n-6) and arachidonic acid (20:4, n-6) are essential for normal skin function and structure, both as eicosanoid precursors and as components of lipids forming cell membranes. Adult human keratinocytes grow optimally in serum-free medium (MCDB 153) that contains no fatty acids. These keratinocytes expand rapidly and produce normal epidermis upon in vivo grafting. Analysis of lipid extracts of epidermis and of cultured keratinocytes was done to determine the fatty acid composition of cells grown in essential fatty acid (EFA)-deficient medium. Gas chromatography and high-performance liquid chromatography analyses were done of the fatty acids in the entire cell and in a thin-layer chromatography separated fraction containing those lipids that form cellular membranes. Comparison of snap-frozen epidermis and epidermal basal cell suspensions to passage 1 to 4 cultures shows that the cells are in an extreme essential fatty acid-deficient state by the first passage. The amount of the saturated fatty acids 16:0, 18:0, and 14:0 is unchanged by culture. The polyunsaturated fatty acids are found to be significantly decreased, the cells balancing their lack with a significant increase in the relative abundance of the monounsaturated fatty acids, 18:1 and 16:1. Greater than 85-90% of the fatty acids was found in lipids associated with membranes and no unusual fatty acids were detected. Because the serum-free medium is fatty acid free and the cells cannot synthesize essential fatty acids, the rapid division of the cells results in the predominance of an extreme EFA-deficient cell type. The essential fatty acid-deficient keratinocyte is an excellent adult, normal epidermal cell model that can be used to study EFA deficiency and the effect of the eicosanoid and fatty acids on cell function and structure.

Animals↗
PubMed1992

Human skin levels of retinoic acid and cytochrome P-450-derived 4-hydroxyretinoic acid after topical application of retinoic acid in vivo compared to concentrations required to stimulate retinoic acid receptor-mediated transcription in vitro.

Metabolism of retinoic acid to a less active metabolite, 4-hydroxyretinoic acid, occurs via cytochrome P-450 isozyme(s). Effect of a pharmacological dose of retinoic acid on the level of retinoic acid in skin and on cytochrome P-450 activity was investigated. A cream containing 0.1% retinoic acid or cream alone was applied topically to adult human skin for four days under occlusion. Treated areas were removed by a keratome and a microsomal fraction was isolated from each biopsy. In vitro incubation of 3H-retinoic acid with microsomes from in vivo retinoic acid treated sites resulted in a 4.5-fold increase (P = 0.0001, n = 13) in its transformation to 4-hydroxyretinoic acid in comparison to in vitro incubations with microsomes from in vivo cream alone treated sites. This cytochrome P-450 mediated activity was oxygen- and NADPH-dependent and was inhibited 68% by 5 microM ketoconazole (P = 0.0035, n = 8) and 51% by carbon monoxide (P = 0.02, n = 6). Cotransfection of individual retinoic acid receptors (RARs) or retinoid X receptor-alpha (RXR-alpha) and a chloramphenicol acetyl transferase (CAT) reporter plasmid containing a retinoic acid responsive element into CV-1 cells was used to determine the ED50 values for stimulation of CAT activity by retinoic acid and its metabolites. Levels of all trans and 13-cis RA in RA-treated tissues were greater than the ED50 values determined for all three RARs with these compounds. Furthermore, the level of all trans RA was greater than the ED50 for RXR-alpha whereas the 4-OH RA level was greater than the ED50 for RAR-beta and RAR-gamma but less than for RAR-alpha and RXR-alpha. These data suggest that there are sufficient amounts of retinoic acid in treated skin to activate gene transcription over both RARs and RXR-alpha.

Administration, Topical↗
PubMed1991

Cellular, immunologic and biochemical characterization of topical retinoic acid-treated human skin.

Histologic and clinical improvement of sun-exposed skin following topical treatment with retinoic acid has been reported. Daily application of retinoic acid typically results within 2-5 d in an erythematous scaling reaction, which lessens with continued usage. The cellular, immunologic, and biochemical basis of this retinoid reaction and its role in the repair of photodamaged skin are not known. To investigate the retinoid reaction in man, we have treated non-sun-exposed skin with 0.1% retinoic acid cream (Retin-A, Ortho Pharmaceutical Corporation, Raritan, NJ) under occlusion for 4 d to induce erythema and then examined changes in 1) histology, 2) expression of cell-surface molecules, 3) the enzymes and second messengers of the phospholipase C/protein kinase C signal-transduction system, 4) levels of eicosanoids, and 5) levels of interleukin-1 protein and mRNA. These parameters were chosen for measurement both because they are indicators of epidermal function and previous studies suggest they may be responsive to retinoic acid treatment. Epidermal cell growth as judged by increased epidermal thickness and mitotic figures was significantly increased in retinoic acid-treated skin compared to vehicle-treated controls. Increased numbers of CD4+ T cells accompanied by prominence of dermal dendrocytes in the papillary dermis and focal keratinocyte expression of intercellular adhesion molecule-1 were observed in retinoic acid-treated biopsies. Phosphoinositide-specific phospholipase C activity and 1,2-diacylglycerol content were also elevated in retinoic acid-treated epidermis. Protein kinase C activity was reduced by one third in both the soluble and membrane fraction, suggesting down-regulation. Surprisingly, in view of the inflammatory nature of the retinoid reaction, no increases were observed in arachidonic acid, its metabolites, interleukin-1 alpha, or interleukin-1 beta. To examine the specificity of the retinoid reaction, subjects were treated with the irritant sodium lauryl sulfate, under conditions that resulted in a reaction clinically similar to that observed with retinoic acid. The histologic alterations induced by sodium lauryl sulfate were found to be indistinguishable from those induced by retinoic acid. These data indicate that, although a wide range of cellular and molecular alterations occur in retinoic acid-treated skin, these changes may not be necessarily specific or unique for retinoic acid.

Cell Adhesion Molecules↗
PubMed1990

Effect of topical cyclosporine rinse on oral lichen planus. A double-blind analysis.

BACKGROUND: Oral lichen planus is a relatively common disorder of the mouth that can be debilitating. It is frequently palliated with topical or systemic corticosteroids and retinoids. These treatments require prolonged use, however, and are not always effective. METHODS: In a double-blind trial, 16 patients with symptomatic oral lichen planus were randomly assigned to receive either topical cyclosporine or its vehicle. The patients swished and expectorated 5 ml of medication (containing 100 mg of cyclosporine per milliliter) three times daily. RESULTS: After eight weeks, the eight recipients of cyclosporine had marked improvement in erythema (P = 0.003), erosion (P = 0.02), reticulation (presence of white lacelike lesions; P = 0.007), and pain (P = 0.002), whereas the eight recipients of vehicle had no change or minimal improvement. After a switch to cyclosporine for eight weeks, the vehicle-treated patients had improvement similar to that seen in the patients who initially received cyclosporine. There were no systemic side effects. In most cases blood cyclosporine levels were low or undertectable. Cyclosporine levels present in specimens of oral mucosa at the end of therapy four hours after the patients swished were similar to the levels previously reported in psoriatic lesions after treatment with systemic cyclosporine (14 mg per kilogram of body weight per day). CONCLUSIONS: As a topical preparation, cyclosporine may be useful in the treatment of oral lichen planus and possibly other cutaneous disorders.

Aged↗
PubMed1990

Sulfasalazine improves psoriasis. A double-blind analysis.

In an 8-week double-blind trial of sulfasalazine for the treatment of moderate-to-severe psoriasis, 23 and 27 patients received the active and placebo tablets, respectively. At the end of the double-blind phase, there were 17 assessable patients receiving sulfasalazine; 7 (41%) had marked improvement, 7 (41%) had moderate improvement, and 3 (18%) demonstrated minimal change. Only 1 patient receiving placebo demonstrated moderate improvement, whereas the rest had minimal improvement or worsening of psoriasis. When the randomization code was broken, patients receiving sulfasalazine were allowed to continue therapy for an additional 4 weeks in an open manner, while those using placebo left the study. Six of 23 patients discontinued sulfasalazine therapy during the double-blind phase because of side effects, 4 due to the development of a cutaneous eruption and 2 due to nausea. Fourteen of 17 patients, who were assessable at the end of the 8-week double-blind phase, completed the additional 4 weeks of sulfasalazine therapy. Of these 14 patients, marked improvement occurred in 8 (57%), moderate improvement in 2 (14%), and minimal improvement in 4 (29%), compared with pretherapy. The low incidence of severe side effects makes sulfasalazine a consideration for oral therapy in patients whose disease severity does not justify use of methotrexate, etretinate, or psoralen plus UV-A, but whose disease severity is too widespread for safe and practical use of topical corticosteroids.

Adult↗
PubMed1989

Topical cyclosporine A inhibits the phorbol ester induced hyperplastic inflammatory response but not protein kinase C activation in mouse epidermis.

Cyclosporine A (CsA) is efficacious in the treatment of psoriasis. Although CsA is known to inhibit T-lymphocyte proliferation in vitro, whether this is its mode of action in psoriasis is uncertain. 12-0-tetradecanoylphorbol-13-acetate (TPA) induces an inflammatory, hyperplastic response in mouse skin, with many of the biochemical and histologic aberrations that occur in psoriatic epidermis. Protein kinase C is the major cellular phorbol ester receptor, and most responses of cells to TPA are mediated by PK-C, which is directly activated by TPA. We therefore have investigated the effects of CsA on pleiotypic responses induced by TPA and whether CsA acts in vivo as a direct inhibitor of PK-C. Simultaneous application of CsA (1.7 mumol) and TPA (10 nmol) to mouse skin significantly reduced inflammatory cell infiltration and increased epidermal thickness induced by TPA treatment alone. CsA had to be applied within 30 min of TPA application in order to have a significant inhibitory effect. Optimal doses of CsA inhibited TPA-induced ODC activity, TGase activity, arachidonic acid release, and interleukin-1 beta (IL-1 beta) mRNA to the same degree (approximately 80%), despite measurement at widely different times (30 min-12 h) required to obtain maximal induction by TPA. CsA did not, however, directly inhibit activation of PK-C by TPA. These data demonstrate that CsA blocks the pleiotypic responses of mouse skin to TPA treatment involving biochemical events, inflammatory cell infiltration, and epidermal hyperplasia. The molecular site(s) of action of CsA appears to be distal to the initial activation of PK-C by TPA and clearly inhibits PK-C inducible events. Furthermore, the above data suggest that CsA may directly affect keratinocytes in vivo.

Administration, Topical↗
PubMed1988

Levels of cyclosporin in epidermis of treated psoriasis patients differentially inhibit growth of keratinocytes cultured in serum free versus serum containing media.

Cyclosporin A, which is a specific immunosuppressive compound, has recently been demonstrated to be of significant benefit in the treatment of psoriasis. Because hyperplasia is a major feature of psoriasis, we have investigated whether this drug acts directly to inhibit keratinocyte growth. We have determined the concentration range of cyclosporin in the epidermis of psoriatic patients undergoing cyclosporin therapy and the effect of this concentration range on the growth of cultured keratinocytes. After 7 days of treatment, psoriatic involved epidermis contained 1.1 +/- 0.3 ng cyclosporin/micrograms DNA. Based on tissue wet weight this is approximately 2.8 micrograms cyclosporin/ml. This value was 10 times that of trough blood samples. On day 3 of treatment, involved epidermis contained 7 times more cyclosporin than scale, while on day 7 this ratio was reduced to 2. This suggests that cyclosporin was initially associated with the lower layers of the epidermis and distributed upward with time. Exposure of adult human keratinocytes, cultured on collagen in the presence of human serum, to cyclosporin (0.1-30 micrograms/ml, 0.4-13-fold higher than lesional cyclosporin) for 2-6 d had no effect on the rate of incorporation of thymidine into DNA. Cyclosporin (1-30 micrograms/ml) also had not effect on the reinitiation of DNA synthesis of quiescent cells subsequent to the reintroduction of serum. In contrast, cyclosporin (1-10 micrograms/ml) inhibited growth of keratinocytes cultured on plastic culture dishes in serum free media (MCDB 153). For a given dose of cyclosporin, cell associated drug was 2-3 times greater in serum free compared to serum containing media. This may contribute in part to the sensitivity of keratinocytes in serum free media to growth inhibition by cyclosporin. These data demonstrate that human epidermis contains a high concentration of cyclosporin after oral administration, and that, under certain conditions, concentrations of cyclosporin within the range found in vivo can inhibit growth of cultured keratinocytes. Because cyclosporin regulates lymphocyte function in vivo and in vitro, the demonstrated antiproliferative effects of cyclosporin on psoriatic keratinocytes in vivo may be due to inhibition of a mononuclear leukocyte-derived keratinocyte growth factor(s) in combination with direct inhibition of keratinocyte growth.

Blood Physiological Phenomena↗
PubMed1988

Determination of 5,12, and 15-lipoxygenase products in keratomed biopsies of normal and psoriatic skin.

Keratomed epidermal tissue from normal individuals and from the lesional and non-lesional skin of psoriasis patients served as source materials for the extraction, separation, and quantitation of eicosanoids that may be important to cutaneous function and pathophysiology. The eicosanoids were extracted in ethanol and buffer, partially purified on SEP-PAKs, separated by reverse phase microbore high-performance liquid chromatography, and quantitated by radioimmunoassay or integration of absorbency peaks obtained by high performance liquid chromatography. The involved areas from psoriasis patients contained a statistically significant seven- to 11-fold increase in the levels of leukotriene B4, 13-hydroxyoctadecadienoic acid-like compound, 15-hydroxyeicosatetraenoic acid compound and 12-hydroxyeicosatetraenoic acid in comparison to normal samples and a three- to sevenfold increase in comparison to uninvolved tissue. The uninvolved areas contained 40% to 100% increases in the levels of these compounds in comparison to normal tissue; these increases were statistically significant except for 13-hydroxyoctadecadienoic acid-like compound. From a single keratome biopsy, multiple eicosanoids can be separated and quantitated; in addition, levels before, during, and after therapy for psoriasis may be compared.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1986

Cyclosporine improves psoriasis in a double-blind study.

In a double-blind trial, 21 patients with severe plaque psoriasis were randomly assigned to receive oral cyclosporine, 14 mg/kg/d, or its vehicle. After four weeks of therapy the 11 cyclosporine recipients had the following response to treatment: two had total clearing and six improved markedly, two moderately, and one minimally; whereas ten vehicle-treated patients showed no change or minimal improvement. Vehicle-treated patients, after a switch to cyclosporine for four weeks, demonstrated impressive improvement similar to that seen in patients who initially received only cyclosporine. Moderate or marked improvement or total clearing was noted in 17 (81%) of 21 and 20 (95%) of 21 after one and four weeks of therapy, respectively. Mitotic figures and leukotriene B4 levels in lesions decreased 86% and 64%, respectively, after seven days of cyclosporine therapy. Mononuclear (including activated T cells) and polymorphonuclear leukocyte infiltrates were markedly reduced in lesions of all patients after seven days of cyclosporine therapy. These results suggest that psoriasis may have an immunologic basis mediated by activated T cells and/or other immune cells; if a long-term regimen with a favorable efficacy-side effect ratio can be determined, cyclosporine would be a significant advance in the treatment of psoriasis.

Adult↗
PubMed1986

Dermis-derived 15-hydroxy-eicosatetraenoic acid inhibits epidermal 12-lipoxygenase activity.

The purpose of the present study was to analyze the metabolism of arachidonic acid (AA) in normal human dermis. After incubating homogenized dermis with exogenous AA, the extracted lipids were isolated by reversed-phase high-performance liquid chromatography. Each chromatographic peak was characterized by its UV absorption spectrum and identified by its coelution with the appropriate authentic standard and by radioimmunoassay of its eluate fraction. Identified compounds were quantitated by integrated optical density. Homogenized human dermis transformed AA into both cyclooxygenase and lipoxygenase products, but predominantly 15-hydroxy-eicosatetraenoic acid (15-HETE). Cultured fibroblasts from normal human dermis also mainly metabolized AA into 15-HETE. To determine whether dermis-derived 15-HETE might modify the AA metabolism of epidermis, normal human epidermis was incubated with dermis. Increasing amounts of dermis resulted in an increasing inhibition of epidermal 12-HETE formation. Similarly, 15-HETE alone induced a dose-dependent decrease of epidermal 12-HETE formation, while the formation of prostaglandin E2 was unchanged. Since 12-HETE possess the ability to elicit skin inflammation and to stimulate epidermal DNA synthesis, 15-HETE formation may be a way whereby dermis regulates important epidermal activities.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1986

In vitro synthesis of 12-hydroxy-eicosatetraenoic acid is increased in uninvolved psoriatic epidermis.

Certain arachidonic acid (AA) metabolites have been detected in psoriatic skin lesions. In this study the capacity of normal epidermis and clinically uninvolved psoriatic epidermis to transform AA into lipoxygenase products was determined in vitro. After incubating homogenized epidermis with exogenous AA, the extracted lipids were isolated by reverse-phase high-performance liquid chromatography. Each chromatographic peak was characterized by its UV absorption spectrum and identified by its coelution with the appropriate authentic standard and by radioimmunoassay of its eluate fraction. Identified compounds were quantitated by integrated UV absorbance. Leukotriene B4 (LTB4) was also identified by neutrophil chemokinesis. Normal epidermis generated 15-hydroxy-eicosatetraenoic acid (15-HETE) and 12-HETE, the latter being more abundant. 5-Lipoxygenase products (LTB4, LTC4, and 5-HETE) were not detected. However, an unknown compound exhibiting a triplet UV absorbtion spectrum with maximum at 274 mm was formed. Its formation was inhibited by 5,8,11,14-eicosatetraynoic acid, but not by indomethacin or a specific 5-lipoxygenase inhibitor (REV 5901). These data suggest that a di-HETE with a triene structure is one possible candidate for the unknown compound. Compared with normal epidermis, the formation of 12-HETE and the unknown di-HETE by uninvolved psoriatic epidermis was increased by 54% and 63%, respectively. The formation of 12-HETE and the unknown di-HETE in uninvolved psoriatic epidermis was stimulated to the same degree in the presence of the phospholipase inhibitor quinacrine. These results indicate that uninvolved psoriatic epidermis has an increased capacity to metabolize free AA into 12-lipoxygenase products.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1986

Selective decrease of 15-hydroxyeicosatetraenoic acid (15-HETE) formation in uninvolved psoriatic dermis.

Epidermis of psoriatic skin lesions is characterized by elevated 5-lipoxygenase and 12-lipoxygenase products. 15-hydroxyeicosatetraenoic acid (15-HETE), the predominant lipoxygenase product in normal dermis, has the potential to inhibit 5-lipoxygenase and 12-lipoxygenase. The purpose of the present study was to determine the capacity of homogenized dermis from uninvolved psoriatic skin to form 15-HETE in vitro. Extracted lipids were separated by reversed-phase high-performance liquid chromatography. Each chromatographic peak was identified by its coelution with authentic standards, by ultraviolet spectrometry, and by radioimmunoassay. Dermis from uninvolved psoriatic skin generated on average 48% less 15-HETE than normal dermis (P less than .01). In contrast, the formation of 12-hydroxyeicosatetraenoic acid was increased by 56% in psoriatic dermis (P less than .01). Prostaglandin E2 formation was similar in normal and psoriatic dermis. Since 15-HETE can inhibit the synthesis of 5-lipoxygenase and 12-lipoxygenase products that possess inflammatory and proliferative capacities, a defective 15-HETE generation in dermis may be of importance for the development of psoriasis.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1983

Decreased urinary polyamines in patients with psoriasis treated with etretinate.

Oral administration of the aromatic retinoid etretinate is effective therapy for psoriasis and other epidermal hyperproliferative disorders. Since polyamine metabolism is known to be important in cell growth and differentiation, we measured urinary levels of the polyamines putrescine, spermidine, and spermine as a reflection of cutaneous polyamine metabolism in 19 psoriatic patients treated with etretinate for 16 weeks. Using thin-layer chromatography, polyamine determinations were performed on urine collected pretherapy, during therapy, and 8 weeks after therapy was concluded. Good to excellent clearing of psoriasis occurred in 18 of 19 patients. All urinary polyamines showed a downward trend in the first week of therapy, prior to significant clinical improvement. At week 16 of therapy, the greatest reduction in mean urinary polyamine content occurred. Mean putrescine levels decreased from pretherapy to week 16 by 27% (p less than 0.001), mean spermidine values fell by 34% (p less than 0.001), and mean spermine levels declined by 37% (p = 0.005). These data are consistent with the hypothesis that etretinate inhibits polyamine biosynthesis.

Adult↗
PubMed1982

Intact epidermal cell assay for ornithine decarboxylase activity.

A procedure measuring the ornithine decarboxylase (ODC) activity and polyamine formation of intact neonatal mouse epidermal cells in culture has been developed and tested. Basal cells prepared from neonatal mouse epidermis were plated on round 15-mm Lux coverslips, placed in Costar 24 well culture clusters and grown at 32 degrees C in M-199 + 13% fetal bovine serum. Before assay the cells were rendered permeable to ornithine 14C and ODC inhibitors using the buffer described by Berger et al. [3]. The slides, covered with adhering cell layers, were then placed in vials, covered with assay buffer and assayed intact for ODC activity. The ODC reaction was terminated by addition of citric acid to the buffer and the amount of 14CO2 released was determined by scintillation counting of a center well filled with trapping agent. The baseline ODC activity of the intact cells was 500-1,000 pmol 14CO2/mg protein/45 min. The validity of this ODC assay procedure using intact neonatal mouse keratinocytes was tested by use of three specific ODC inhibitors and by measuring the formation of polyamines from uniform labeled ornithine. The results indicated that authentic ODC activity was measured and preserved in this intact neonatal mouse epidermal cell assay. This technique holds promise for future studies of epidermal cell regulation of ODC and polyamine synthesis and studies of the multiple ornithine metabolites and conjugates formed, using a highly manipulable in vitro system.

Animals↗