Involvement of protein kinase C activation in ornithine decarboxylase gene expression in primary culture of newborn mouse epidermal cells and in skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate

The role of protein kinase C in ornithine decarboxylase (ODC; EC 4.1.1.17) gene expression in primary culture of newborn mouse epidermal cells (MEC) from BALB/c mice and in skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA) in female CD-1 mice was determined. A time course and the dose-response curves of ODC induction paralleled that of ODC mRNA induction by TPA in MEC. TPA treatment did not elicit any change in the size of ODC mRNA. The magnitude of ODC induction was proportional to the amount of ODC mRNA increased by TPA. TPA (2 X 10(-7) M) failed to induce ODC activity in MEC plated in Ca2+-deprived medium; TPA induction of ODC could be resumed upon Ca2+ restoration in the medium. 1-Oleoyl-2-acetylglycerol, a membrane-permeable diacylglycerol which activates protein kinase C, induced at the same rate both ODC activity and the amount of ODC mRNA in MEC. Phospholipase C, which releases diacylglycerol from membrane phospholipids, also induced ODC activity; 0.02 units of phospholipase C per ml led to about a 50-fold increase in ODC activity at 6 h after treatment. Phospholipase A2 was ineffective. Phospholipase C-induced ODC activity correlated with an increased level of ODC mRNA. Furthermore, palmitoylcarnitine, an inhibitor of protein kinase C, inhibited epidermal ODC induction and the increased level of ODC mRNA by TPA. Also, palmitoylcarnitine inhibited skin tumor promotion by TPA; application of 3 mumol of palmitoylcarnitine in conjunction with each promotional treatment with 10 nmol of TPA to the initiated skin of female CD-1 mice inhibited tumor formation. Taken together, we conclude that activation of protein kinase C may be an early event in ODC gene transcription and skin tumor promotion by TPA.

Increased mouse epidermal ornithine decarboxylase activity by the tumour promoter 12-O-tetradecanoylphorbol 13-acetate involves increased amounts of both enzyme protein and messenger RNA

Evidence was sought that the tumour promoter 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced mouse epidermal ornithine decarboxylase (ODC, EC 4.1.1.17) activity involves both increased ODC mRNA and ODC protein. Application of 10 nmol of TPA to mouse skin led to a dramatic increase in soluble epidermal ODC activity which paralleled an increase in amount of enzymically active ODC protein as determined by gel electrophoresis of immunoprecipitated difluoromethyl[3H]ornithine-bound ODC. Application of TPA to mouse skin also resulted in an increase in ODC mRNA measured by dot-blot analysis using a radiolabelled cDNA probe. ODC mRNA induction preceded the increase in ODC activity by TPA. TPA-increased ODC mRNA displayed a single major band of 2.1 kilobases in size identified by the Northern blotting procedure.

Induction of mouse epidermal ornithine decarboxylase by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate: dependence on calcium availability

The role of calcium in epidermal ornithine decarboxylase (ODC) induction by 12-O-tetradecanoylphorbol-13-acetate (TPA) was determined in adult mouse skin pieces incubated in serum-free minimal essential medium (MEM). Addition of TPA to skin pieces incubated in serum-free MEM, which contains 1.82 mM Ca2+ and 0.83 mM Mg2+, resulted in about a 200-fold increase in epidermal ODC activity at about 8 h after TPA treatment. TPA failed to induce epidermal ODC in skin pieces incubated in calcium-free medium. Similarly, chelation of extracellular calcium by ethyleneglycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA) prevented ODC induction by TPA, which could be resumed upon calcium restoration in the medium. Furthermore, calcium ionophore A23187, which facilitates efflux of Ca2+ across cellular membranes, induced ODC activity in incubated skin pieces. Epidermal ODC activity increased by TPA appears to be the result of an increase in both the amount of ODC protein and the level of hybridizable ODC messenger. Inhibition of the induction of ODC activity by EGTA was the result of the inhibition of the amount of active ODC protein and the level of ODC mRNA.

Modulation of mouse skin tumor promotion by dietary 13-cis-retinoic acid and alpha-difluoromethylornithine

The effects of dietary supplementation of 13-cis-retinoic acid (13-cis-RA) and alpha-difluoromethylornithine (DFMO) in the drinking water on 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted skin tumor formation was determined. Administration of 13-cis-RA in the diet and DFMO in the drinking water was started 1 week and 2 days before the first TPA application to the dimethylbenz[a]anthracene-initiated skin of either female CD-1 or SENCAR mice, respectively. Dietary 13-cis-RA failed to inhibit both the tumor yield and the incidence; papillomas per mouse at 0, 5, 50, 100 and 200 mg/kg diet 13-cis-RA doses were 25, 30, 22, 28 and 25 respectively at 18 weeks of promotion treatment and at all doses 100% of the mice bore papillomas. However, dietary 13-cis-RA dramatically reduced the size of skin tumor promoted with TPA. 13-Cis-RA at doses of 5, 50, 100 and 200 mg/kg diet inhibited skin papillomas (greater than 4 mm diameter) per mouse by 28, 55, 76 and 93%, respectively. Retinoid treatment did not affect body weight gains and the survival was more than 80% in all groups. In accord with our previous findings, DFMO when given in drinking water, was a very effective inhibitor of mouse skin tumor promotion by TPA; DFMO at 0.25% concentration inhibited the number of papillomas by 50%. Inhibition of skin tumor promotion by combined treatments with dietary 13-cis-RA (100 mg/kg) and DFMO (0.25%) in the drinking water was possibly additive. The retinoid and DFMO preclude TPA-increased ornithine decarboxylase (ODC) activity and the accumulation of putrescine by differential effects on ODC, an enzyme associated with skin tumor promotion by TPA.

Hypesthetic-ataxic-hemiparesis in thalamic hemorrhage

Acute onset hypesthetic-ataxic-hemiparesis is described in two hypertensive patients. Computed tomography (CT) showed an area of increased attenuation consistent with blood in contralateral thalamus. The pathophysiologic implications of the cerebellar and pyramidal system in thalamic hemorrhage is discussed.

Relative efficiency of two mating systems and selection procedures for yield improvement in wheat (Triticum aestivum L.)

The relative efficiences of the biparental mating systems and selfing series in connection with phenotypic and geno-phenotypic selection procedures were evaluated for yield improvement in a cross 'HP1102' X 'CPAN 1681' of wheat. Two selection cycles having a 4 per cent selection intensity for grain yield were carried out following both selection procedures under the two mating systems. Following these selection procedures, a greater improvement for grain yield could be achieved with the biparental mating system than with the selfing series. During the first selection cycle, the geno-phenotypic selection procedure had an edge over phenotypic selection procedure. The realized response due to the second cycle of selection and the predicted response for the third selection cycle indicated that the phenotypic selection procedure is more efficient than the geno-phenotypic selection procedure. It is suggested that selection following intermating in early segregating generations is able to overcome several inherent limitations of the simple pedigree method as it is possible to increase genetic variation and to concentrate favourable genes and gene combinations for grain yield. An increase in grain yield was, in general, accompanied by an increase in plant height, peduncle length, 100 grain weight, tiller number and biological yield. Therefore, it is suggested that an index comprised of grain yield, plant height, tiller number, grain weight and biological yield could be used for selecting high yielding genotypes of suitable height.

Dose and schedule of oral retinoic acid and indomethacin needed to effectively inhibit phorbol ester-induced epidermal ornithine decarboxylase activity

Currently there is no well-defined biological parameter or marker to help define agents, doses, and dose schedules for human cancer chemoprevention trials. Induction of ornithine decarboxylase, the rate limiting enzyme in the polyamine biosynthetic pathway, has been shown to be an essential aspect of mouse skin tumor promotion. Supplementary information suggest that this enzyme is an important aspect of carcinogenesis in other organ systems and in other animals (including humans). We have developed an assay system which effectively measured tumor promoter (TPA)-induced ornithine decarboxylase activity on 3-4 mm skin samples from mice and humans. Using this system we evaluated the doses and dose schedules of retinoic acid and indomethacin needed to effectively inhibit ornithine decarboxylase activity. Our data suggest that the doses and schedules of these compounds needed to inhibit ornithine decarboxylase activity would be toxic in humans.

Inhibition of ornithine decarboxylase activity by small doses of alpha-difluoromethylornithine

The induction of ornithine decarboxylase (ODC) appears to be an important aspect of carcinogenesis. Agents which inhibit ODC have been shown to preclude cancer formation in many organ systems. We studied the dose and dose schedule of alpha-difluoromethylornithine (DFMO), a suicide inhibitor of ODC, needed to effectively inhibit ODC activity in mice. Our data demonstrate that doses many-fold lower than comparable maximal tolerated doses in humans can inhibit ODC activity in mice. In addition, a simplified, once daily dosage of DFMO appears adequate.

Inhibition of phorbol ester-caused synthesis of mouse epidermal ornithine decarboxylase by retinoic acid

The mechanisms by which topically applied retinoic acid to mouse skin inhibits tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced epidermal ornithine decarboxylase activity were analyzed. Retinoic acid inhibition of the induction of epidermal ornithine decarboxylic activity was not the result of nonspecific cytotoxicity, production of a soluble inhibitor of ornithine decarboxylase, or direct effect on its activity. In addition, inhibition of TPA-caused increased ornithine decarboxylase activity does not appear to be due to enhanced degradation and/or post-translational modification of ornithine decarboxylase by transglutaminase-mediated putrescine incorporation. We found that retinoic acid inhibits the synthesis of ornithine decarboxylase caused by TPA. Application of 10 nmol TPA to mouse skin led to a dramatic induction of epidermal ornithine decarboxylase activity which was paralled by increased [3H]difluoromethylornithine binding and an increased incorporation of [35S]methionine into the enzyme. Application of 17 nmol retinoic acid 1 h prior to application of 10 nmol TPA to skin resulted in inhibition of the induction of activity which accompanied inhibition of [3H]difluoromethylornithine binding and [35S]methionine incorporation into ornithine decarboxylase protein as determined by the tube-gel electrophoresis of the enzyme immunoprecipitated with monoclonal antibodies to it. Inhibition of ornithine decarboxylase synthesis was not the result of the inhibitory effect of retinoic acid on general protein synthesis. The results indicate that retinoic acid possibly inhibits TPA-caused synthesis of ornithine decarboxylase protein selectively.

In vitro induction of human skin ornithine decarboxylase by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate

A method was developed for the in vitro induction by 12-O-tetradecanoylphorbol-13-acetate (TPA) of ornithine decarboxylase (ODC) activity in human skin punch biopsy samples. Addition of TPA to 1 ml serum-free minimum essential medium containing a single 3-mm human skin punch biopsy sample obtained from a surgical specimen resulted in an induction of ODC activity with a peak activity at 5 hours after TPA addition. In vitro induction of human epidermal ODC activity was dependent on the TPA concentration in the medium; about a twofold increase in ODC activity was observed 6 hours after the addition of 0.1 microM TPA, and about a fivefold increase in ODC activity was observed with 1 microM TPA. TPA also caused about a fivefold to sixfold increase in ODC activity in 3-mm skin punch biopsy samples from healthy volunteers. Human skin punch biopsy samples remained responsive to TPA induction of ODC activity even when stored in serum-free medium at 4 degrees C for 24 hours. A similar degree of induction of ODC activity by TPA was observed whether whole unfractionated human epidermis or a soluble epidermal extract was used for ODC assays. Increased ODC activity was the result of the increase in enzymatically active ODC protein, quantitated by a [3H]difluoromethylornithine-binding assay. Thus human skin, like mouse skin, is responsive to TPA for ODC induction.

Inhibition of phorbol ester--induced human epidermal ornithine decarboxylase activity by oral compounds: a possible role in human chemoprevention studies

Extensive animal data have suggested that, in some systems, the induction of ornithine decarboxylase (ODC) is an essential, although not sufficient, aspect of tumor promotion and that compounds that inhibit ODC can inhibit tumor formation. Using fasting human volunteers, we report that human epidermal and dermal ODC are consistently induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in a manner similar to that seen in mouse skin. There is a marked intersubject variation in TPA-induced epidermal ODC activity levels. Orally administered compounds significantly inhibited TPA-caused human epidermal ODC induction. These data may be useful in the further development of drugs, doses, and dose schedules for use in human cancer chemoprevention studies.

Evidence against involvement of the human erythrocyte plasma membrane Ca2+-ATPase in Ca2+-dependent K+ transport

Two tests were performed to assess the relationship between the Ca2+-activated K+ channel and the Ca2+-pumping ATPase in human erythrocytes. Antibodies against the purified ATPase inhibited the ATPase in resealed erythrocytes, but had no effect on the K+ channel (as assessed by Rb+ efflux). Reconstituted liposomes containing the purified active Ca2+-pumping ATPase showed no Ca2+-activated Rb+ influx. Both of these results suggest that some molecule other than the Ca2+-ATPase is responsible for the K+ channel.

Tumor promoter 12-O-tetradecanoylphorbol-13-acetate receptors in normal human transitional epithelial cells

As a prelude to study the promotion with TPA of in vitro transformation of human urothelial cells (HUC) in culture, we characterized tumor promoter TPA receptors in primary cultures of HUC. [3H]TPA bound specifically to intact living HUC; maximum specific binding was attained in approximately 30 min at 37 degrees C. [3H]TPA bound to HUC in a saturable and competitive manner. Scatchard analysis of specific binding to intact cells displayed a single slope corresponding to an equilibrium dissociation constant (Kd) of 0.56 nM; at saturation TPA-binding capacity was 2.37 pmol/10(6) HUC (1.43 X 10(6) sites per cell). [3H]TPA bound specifically and with high affinity to the particulate fractions of HUC; binding was both saturable and reversible. Saturation of the specific binding of [3H]TPA occurred at approximately 1 nM at 4 degrees C. Scatchard analysis of specific binding to the particulate fraction displayed a single slope corresponding to a Kd of 1.08 nM; at saturation TPA-binding capacity was 2.05 pmol/mg protein (750 000 molecules per HUC). [3H]TPA binding was inhibited by the biologically active phorbol ester, phorbol didecanoate, whereas inactive phorbol did not compete for TPA binding. Binding was not affected by sodium saccharin, epidermal growth factor, retinoic acid or dexamethasone. [3H]TPA bound specifically to the HUC cytosolic fraction but only in the presence of calcium and phosphatidylserine. Calcium-activated and phospholipid-sensitive protein kinase activity was detected in HUC fractions. These results indicate the presence of high-affinity specific receptors for TPA in HUC.

Hyperthermia and polyamine biosynthesis: decreased ornithine decarboxylase induction in skin and kidney after heat shock

The effect of hyperthermia treatments on ornithine decarboxylase (ODC) induction in mouse tissue was determined both in vitro and in vivo. In vitro, the addition of 12-0-tetradecanoylphorbol-13-acetate (TPA) to adult mouse skin pieces incubated at 37 degrees C in serum-free MEM led to a dramatic increase in epidermal ODC activity 5 hours following treatment. In contrast, incubation temperatures of 40 degrees C for the entire 5 hour incubation period rendered the skin pieces unresponsive to TPA for ODC induction. This inhibition of ODC induction was not the result of thermal skin kill, inactivation of TPA, or a general effect on epidermal protein synthesis. The inhibition of ODC induction could be reversed by switching the incubation temperature back to 37 degrees C. In vivo, raising the core body temperature in male mice to 41 degrees C for 1 hour resulted in a 78% decrease in kidney ODC activity. The kidney DNA synthesis and protein synthesis remained unaltered following the whole body hyperthermia treatments.

Acute ascending motor paralysis due to rabies: a clinicopathological report

An unusual presentation of a not so uncommon disease is described. Practical difficulties in arriving at a diagnosis of paralytic rabies are discussed. An enquiry of exposure and suspicion of rabies in atypical Landry's paralysis is stressed. The importance of autopsy to confirm either of the diagnoses is emphasized.

Effects of affinity-purified antibodies on the Ca2+ pumping ATPase of erythrocyte membranes

Antibodies raised in rabbits against the purified erythrocyte membrane Ca2+ pumping ATPase were affinity-purified using an ATPase-Sepharose column. Addition of a few molecules of the purified antibody per molecule of ATPase was sufficient to inhibit the ATPase activity. Extensively washed ghosts or preincubated pure ATPase sometimes develop an appreciable Mg2+-ATPase activity. In such cases, the antibodies inhibited the Mg2+-ATPase as well as the Ca2+-ATPase. This is consistent with the hypothesis that a portion of the Mg2+-ATPase activity of ghosts is derived from the Ca2+-ATPase. When nitrophenylphosphatase activity was observed, both Mg2+- and Ca2+-stimulated activities were observed. Only the Ca2+ activity was inhibited by the antibodies, confirming that this activity is due to the Ca2+ pump, and suggesting that the Mg2+-nitrophenylphosphatase is due to a separate enzyme. Amounts of antibody comparable to those which inhibited the Ca2+-ATPases had no effect on the Na+-K+-ATPase; 4-fold higher amounts of antibody significantly stimulated the Na+-K+-ATPase, but this effect of the antibody was not specific: Immunoglobulins from the nonimmune serum also significantly stimulated the Na+-K+-ATPase. In resealed erythrocyte membranes, antibodies incorporated into the ghosts inactivated the Ca2+-ATPase, while antibodies added to the outside had no significant effect.

Effects of local anesthetics on phorbol ester-induced ornithine decarboxylase activity in mouse and human skin

In preparation for experiments to determine the effects of various orally administered compounds on human skin ornithine decarboxylase (ODC) activity, it was observed that intradermal lidocaine hydrochloride inhibited 12-0-tetradecanoylphorbol-13-acetate (TPA)-induced ODC. Topically applied ethyl chloride had variable and unpredictable effects on ODC induction. Adequate local anesthesia can be obtained by using intradermal 1.0% procaine hydrochloride or normal saline; neither of these agents inhibited TPA induction of epidermal ODC activity in incubated human skin punch biopsies.

Two Ca2+-requiring p-nitrophenylphosphatase activities of the highly purified Ca2+-pumping adenosinetriphosphatase of human erythrocyte membranes, one requiring calmodulin and the other ATP

The highly purified Ca2+-pumping ATPase from human erythrocyte membranes displays two p-nitrophenylphosphatase (NPPase) activities: one of these requires calmodulin and low concentrations of Ca2+, while the other requires ATP and higher Ca2+ concentrations. The free Ca2+ concentrations required for the expression of the two NPPase activities differed very substantially. Both activities required high free Mg2+ concentrations and displayed simple hyperbolic kinetics toward p-nitrophenyl phosphate (NPP) with a Km in the range of 5-20 mM. Study of the dependence of the calmodulin-stimulated NPPase on Mg2+ and NPP indicated that the Mg-NPP complex is not the substrate of the enzyme. Under conditions optimal for ATP-requiring NPPase (1 mM free Ca2+), the Ca2+-ATPase displayed simple hyperbolic kinetics with a low Km for ATP. NPP competitively inhibited this activity, and the apparent Ki for NPP was less than 1 mM, much lower than the Km for NPP as a substrate. If NPP were inhibiting the ATPase by binding at the same site at which NPP is hydrolyzed, the apparent Ki for NPP as inhibitor would be the same as the Km for NPP as substrate. (Under these circumstances, the apparent Ki and the Km can be directly compared, since NPP was being hydrolyzed under both circumstances.) Since Ki was much lower than Km, NPP must have been inhibiting at another site; thus, these data show the existence of two types of NPP sites on the enzyme, one at which NPP is hydrolyzed and the other at which it inhibits ATP hydrolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

5-HIAA in cerebrospinal fluid of patients with status epilepticus

Cerebrospinal fluid concentration of 5-hydroxyindolacetic acid (5-HIAA) was determined in 15 patients soon after recovery from status epilepticus. Similarly, patients with generalised epilepsy and persons without epilepsy, serving as controls, were also studied. The level of 5-HIAA was significantly reduced in all epileptic patients with or without status epilepticus, as compared with the nonepileptic control group. However, there was no statistical difference between patients with status epilepticus and those with generalised epilepsy. Among patients with epilepsy, low 5-HIAA levels in CSF could not be correlated with frequency or severity of seizures, or with antiepileptic drugs. A link between CSF 5-HIAA and susceptibility of humans to epilepsy may indicate a possible future therapeutic approach.

Specific binding, stimulation of rodent urinary bladder epithelial ornithine decarboxylase, and induction of transitional cell hyperplasia by the skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate

The effects of intraurethral or i.p. administration of a mouse skin tumor promoter phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), on rodent urinary bladder transitional epithelium were studied. TPA, when instilled into the urinary bladder of inbred rats (female Fischer, F344) or mice (C3H, ICR, C57BL X DBA/2 F1) at a dose as low as 0.16 nmol, led to a significant (about 10-fold) increase in bladder ornithine decarboxylase (EC 4.1.1.17) (ODC) activity. Peak ODC activity was observed at about 6 hr, and enzyme activity returned to base levels about 14 hr after intravesical TPA. Administration of TPA i.p. in dimethyl sulfoxide also induced vesical ODC at 4 hr after treatment. The magnitude of vesical ODC induction correlated well with the ability of a series of phorbol esters to promote mouse skin tumor formation (TPA greater than phorbol didecanoate greater than phorbol dibenzoate, and phorbol diacetate or phorbol did not induce bladder ODC activity). Mezerein, a second stage mouse skin tumor promoter, induced urinary bladder ODC as much as TPA did. Increased ODC activity by TPA was the result of an increased amount of ODC protein localized mostly (greater than 60%) in urinary bladder mucosa. Intraurethrally administered TPA induced transitional cell hyperplasia starting at Day 2, and it persisted for about 7 days. The urothelium regained normal histology 13 days after TPA treatment. TPA bound specifically and with high affinity to murine bladder mucosa and muscularis particulate preparations. Scatchard analysis of mucosal binding revealed a Kd of 0.82 nM; at saturation, 2.43 pmol were bound per mg protein. Since TPA binds specifically to urinary bladder epithelium, and the induction of ODC activity is one of the properties of tumor promoters, one may conclude that TPA may promote urinary bladder carcinogenesis. Intravesical saccharin also induced urinary bladder ODC activity, but TPA at equimolar quantity was far more potent than saccharin. Thus TPA, being a structurally well-defined molecule, may be a useful compound to study the phenomenon of the tumor promotion stage in urinary bladder carcinogenesis.

Inhibition of mouse skin tumor promotion and of promoter-stimulated epidermal polyamine biosynthesis by alpha-difluoromethylornithine

Application of the tumor-promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA) to mouse skin leads to a manifold induction of ornithine decarboxylase (ODC) activity within 5 hr and an increased accumulation of putrescine. The relevance of these TPA-induced changes to the mechanism of tumor promotion was investigated using alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC. DFMO applied to mouse skin (0.3 mg in 0.2 ml of solvent) or administered in the drinking water (1%) in conjunction with skin tumor promotion by TPA inhibited the formation of mouse skin papillomas by 50 and 90%, respectively. TPA-induced ODC activity and the accumulation of putrescine were almost completely inhibited. DFMO given in the drinking water decreased spermidine levels, but DFMO treatment by any route did not alter the spermine levels of mouse epidermis. DFMO decreased TPA-induced hyperplasia by 25 to 40%, and the TPA-caused increases in DNA synthesis and mitotic index were inhibited by 60 and 50%, respectively. Therefore, in mouse epidermis, enhanced cell proliferation can be dissociated from ODC induction and the accumulation of putrescine. At the tested dose levels and routes of administration, DFMO did not inhibit the inflammatory response to TPA in several tissues. These results provide evidence for an essential role of ODC induction and the accumulation of putrescine in tumor promotion by TPA and add strength to the proposal that DFMO may be a promising drug for the prevention and treatment of cancer in human beings.

Inhibition of 7-bromomethylbenz[a]anthracene-promoted mouse skin tumor formation by retinoic acid and dexamethasone

Retinoic acid, a potent inhibitor of mouse skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate, fails to inhibit tumor formation by the complete carcinogen, 7, 12-dimethylbenz[a]anthracene (DMBA). To obtain further clues about the nature of the mechanism of the carcinogenic process as well as the mechanism of the effect of retinoic acid on tumor promotion, the effect of retinoic acid and two other modifiers (dexamethasone and 7,8-benzoflavone) of tumor formation on tumor promotion by 7-bromomethylbenz[a]anthracene (BrMBA) was determined. BrMBA, a structural analogue of DMBA, is a weak mouse skin tumor-initiating agent but is a good skin tumor promoter. Application of 10, 100, and 200 nmol of BrMBA twice weekly to DMBA-initiated skin resulted in 0, 1.6, and 2.5 papillomas per mouse, and 0, 44, and 60% of mice had papillomas at the 25th week of promotion treatment, respectively. Application of 17 nmol of retinoic acid or 76 nmol of dexamethasone 30 min prior to each twice weekly application of 100 nmol of BrMBA to DMBA-initiated skin inhibited the formation of skin papillomas by 73 and 100%, respectively. 7,8-Benzoflavone, at a 367-nmol dose, did not inhibit tumor promotion by BrMBA. Application of 200 nmol of BrMBA to mouse skin induced epidermal ornithine decarboxylase activity; a peak activity was observed between 8 and 18 hr following BrMBA treatment. Application of 17 nmol of retinoic acid or 76 nmol of dexamethasone inhibited the induction of ornithine decarboxylase activity by BrMBA. 7,8-Benzoflavone did not inhibit the induction of ornithine decarboxylase activity by BrMBA. Retinoic acid and dexamethasone, which inhibit tumor promotion by 12-O-tetradecanoylphorbol-13-acetate, also inhibited tumor promotion by BrMBA, but the nature of the mechanism of tumor promotion by BrMBA is unclear; BrMBA did not inhibit specific binding of 12-O-[3H]tetradecanoylphorbol-13-acetate to the cellular membrane fraction of mouse epidermis.

Purification of the Ca2+-and Mg2+-requiring ATPase from rat brain synaptic plasma membrane

A Ca2+-ATPase (Ca2+- and Mg2+-requiring ATPase) was purified from a synaptic plasma-membrane fraction of rat brain. This enzyme had properties similar to those of plasma-membrane Ca2+-ATPases from other organs: its splitting of ATP was dependent on both Ca2+ and Mg2+, it bound in a Ca2+-dependent fashion to calmodulin-Sepharose and it cross-reacted with specific antibodies raised against human erythrocyte-membrane Ca2+-ATPase. It had an apparent Mr of 138 000, similar to those of plasma-membrane ATPases from human erythrocyte and from dog heart sarcolemma. Previous high-Ca2+-affinity ATPases observed in brain had Mr 100 000; in at least one case, such an ATPase probably represented a different type of enzyme, derived from coated vesicles.

Molecular properties of calcium-pumping ATPase from human erythrocytes

The Ca2+-pumping ATPase from human erythrocyte membranes, purified by the method previously reported [Niggli, V., Penniston, J. T., & Carafoli, E. (1979) J. Biol. Chem. 254, 9955-9958], was freed of minor impurities by extensive washing while bound to the calmodulin-Sepharose column. The pure enzyme showed a single band of Mr 138000, which contained no stainable carbohydrate. The enzyme retained calmodulin-stimulable ATPase activity; with appropriate assay conditions, an activity of 21.2 mumol/(mg x min) was obtained. Amino acid analysis showed that the ATPase had a larger proportion of polar amino acids than do other integral membrane proteins. Despite this, the ATPase showed a tendency to form dimers and higher aggregates even in the presence of sodium dodecyl sulfate and urea. The enzyme required Mg2+ but showed little activity unless a second ion was added. With regard to this second ion, the enzyme responded to alkaline earth metal ions in the order Ca2+ greater than Sr2+ much greater than Ba2+. It was highly specific for ATP and was stimulated by Na+ or K+; in all of these properties it resembled the enzyme in unfractionated membranes. Limited proteolysis using trypsin yielded, at short times, many fragments of various molecular weights; continued proteolysis resulted in two trypsin-resistant fragments of Mr 81000 and 33500. Analysis of the time course of proteolysis indicated that the ATPase existed in two or more conformations that had differing susceptibilities to proteolysis. It is suggested that these correspond to active and inactive conformers of the enzyme.

Effect of colchicine on the uptake of prolactin and insulin into Golgi fractions of rat liver

In previous studies we have shown that 125I-labeled prolactin is taken up by a receptor-dependent process and concentrated in an intact form in Golgi elements from female rat liver (J. Biol. Chem., 1979, 254:209-214). In this study we have examined the effect of colchicine on this uptake process into Golgi elements. Colchicine [25 mumol (10 mg)/100 gm body wt] was injected intraperitoneally in adult female rats, and hepatic Golgi fractions were prepared at 1, 2, and 3 h postinjection. The enzyme recoveries and morphological appearance of fractions from colchicine-treated and control (alcohol alone) animals were similar. At times greater than 1 h after colchicine there was a marked (greater than 60%) inhibition of uptake of 125I-ovine prolactin (125I-oPRL) into Golgi light and intermediate fractions but no inhibition of uptake into Golgi heavy and plasmalemma elements. At times from 2 to 45 min postinjection, 125I-oPRL was extracted from Golgi elements and found to be largely intact as judged by rebinding to receptors. The inhibitory effect of colchicine was seen at doses ranging from 0.25 mumol to 25 mumol/100 g body wt. Vincristine also inhibited 125I-oPRL uptake into the Golgi light and intermediate fractions but lumicolchicine had no inhibitory effect. There was a smaller effect of colchicine both at early (1 h) and later (3 h) times on the extent and pattern of 125I-insulin uptake. Colchicine treatment did not produce a significant change in lactogen receptor levels in the Golgi fractions. These results demonstrate that colchicine treatment inhibited the transfer of prolactin into Golgi vesicular elements. The much smaller effect on insulin uptake suggests that there may be differences in the manner in which the two hormones are handled in the course of internalization.

The differential effects of retinoic acid and 7,8-benzoflavone on the induction of mouse skin tumors by the initiation-promotion protocol and by the complete carcinogenesis process

The biology of tumor formation by the initiation-promotion protocol differs from that of the complete carcinogenesis process. In the latter case, the latency period is longer and tumor yield is less, but carcinomas appear much earlier. Retinoic acid, a potent inhibitor of both the induction of ODC activity and tumor promotion by TPA, failed to inhibit both the induction of ODC activity and tumor formation by DMBA. 7,8-Benzoflavone, which did not inhibit the induction of ODC activity by TPA, inhibited the induction of ODC activity and tumor formation by DMBA. The results indicate that: (a) mechanism of the induction of ODC activity and tumor formation by a complete carcinogen appears to be different from that of the tumor promoter TPA; (b) DMBA-induced ODC activity may be an important component of the mechanism of DMBA carcinogenesis; and (c) although there is a wealth of data that indicate the efficacy of the retinoids in the prevention of a variety of cancers in experimental animals, including mammary carcinogenesis by DMBA (3,5), the present results and those reported by others (2) are not in agreement with a universal effect of retinoic acid in the prevention of carcinogenesis.

Characterization of arginase activity from mouse epidermis and its relation to ornithine decarboxylase induction by the tumor-promoting agent, 12-O-tetradecanoylphorbol-13-acetate

Arginase, which catalyzes the cleavage of L-arginine to urea and ornithine, was detected in both soluble and particulate fractions of mouse epidermis. In a typical experiment, about 75 and 25% of the total arginase activity was associated with the soluble (100 000 X g supernatant) and the washed particulate fraction, respectively. Both soluble and particulate enzymes required the presence of divalent Mn2+ for activity. Arginase activity was increased by about 50% in the particulate fraction, but not in the soluble fraction, by preheating the fractions at either 50 or 55 degrees C in the presence of 15 mM MnCl2. Enzyme activity in both fractions, in the absence of 15 mM MnCl2, dropped precipitously during heating. A comparison of the nature of arginases in the soluble and particulate fractions revealed similar Km values (13 mM) and pH optima (9.5) and identical heat denaturation curves. Application of 10 nmol of 12-O-tetradecanoylphorbol-13-acetate to mouse skin did not increase arginase activity in either fraction over a period of 24 h. In contrast, there was a large increase in ornithine decarboxylase activity in the soluble fraction 4.5 h after treatment. Mouse epidermal ornithine decarboxylase activity was much less than arginase activity and was predominantly localized in the soluble fraction. These results indicate that the normal level of arginase activity is not a limiting factor for the stimulation of polyamine biosynthesis by TPA. High arginase activity in mouse epidermis may play a role in providing ornithine for polyamine biosynthesis and in the production of glutamate and proline as well as in the production of keratinous proteins.

Intracellular hormone receptors: evidence for insulin and lactogen receptors in a unique vesicle sedimenting in lysosome fractions of rat liver

Previous studies have established the presence of polypeptide hormone receptors in Golgi fractions from rodent liver. In this study we attempted to identify peptide hormone receptors in other intracellular elements, particularly lysosomes. Tritosomes were prepared by a standard procedure, and highly purified secondary lysosomes were prepared by fractionating the L fraction of rat liver in a discontinuous metrizamide gradient into subfractions L1 to L4. Binding of 125I-labeled insulin and 125I-labeled somatotropin was studied with membranes prepared from osmotically shocked fractions. The L2 and L3 fractions, virtually devoid of galactosyltransferase (UDP galactose:2-acetamido-2-deoxy-D-glucosylglycopeptide galactosyltransferase, EC 2.4.1.38) but highly enriched in acid phosphatase [orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2], appeared as classical secondary lysosomes by electron microscopy. When compared with Golgi fractions, the level of specific binding per 50 micrograms of protein of 125I-labeled somatotropin in L2 and L3 was 1/3, whereas that of 125I-labeled insulin was comparable. L1, which was reduced in acid phosphatase and increased in galactosyltransferase activities, showed higher hormone binding than did L2 and L3. This was not attributable to Golgi fraction contamination, as evident by specific binding/galactosyltransferase ratios. Binding to tritosome membranes could be largely accounted for by variable contamination with Golgi fractions as judged by specific binding/galactosyltransferase ratios. To clarify the distribution of receptor sites in lysosomal preparations, we fractionated the entire L fraction on a continuous Percoll gradient. Acid phosphatase and galactosyltransferase activities were segregated to the high and low density ranges of the gradient, respectively; however, the fractions enriched in hormone binding were of intermediate density, distinct from Golgi and lysosomal biochemical markers. We conclude that intracellular receptors are found not only in galactosyltransferase-containing very low density lipoprotein-marked Golgi vesicles but also in a unique vesicle of intermediate density between classical Golgi and lysosomal structures.

A high affinity Ca2+-stimulated and Mg2+-dependent ATPase in rat corpus luteum plasma membrane fractions

Plasma membrane fractions from rat corpus luteum contain two kinds of Ca2+-stimulated ATPase, one having a high affinity for Ca2+, the other a low affinity for Ca2+. The high affinity ATPase had a specific Ca2+ requirement with a K 1/2 of 0.2 to 0.3 microM; it had a Vmax of 105 nmol min-1 mg-1 and distributed, upon subcellular fractionation, with recognized plasma membrane enzymes. The properties of this enzyme indicate that it is a CA2+ extrusion pump. The low affinity pump (K 1/2 for Ca2+, about 15 microM) was nonspecific, being stimulated equally well by Ca2+ of Mg2+; its function is unknown. Although the high affinity ATPase resembled the erythrocyte Ca2+-pumping ATPase in the properties mentioned above, it differed in that it failed to respond to Mg2+ or calmodulin. The lack of response to Mg2+ was due to the enzyme's retention of endogenous Mg2+; it did, after incubation with chelators, show a Mg2+ requirement. However, we were unable to show any effect of added calmodulin or trifluoperazine. This failure may be related to the high content of tightly bound calmodulin in these membranes. Much of this calmodulin could not be extracted even by washing with 1 mM EGTA and/or 0.1% (w/v) Triton X-100. This enzyme, the erythrocyte enzyme, and the adipocyte plasma membrane Ca2+ ATPase all belong to the class of Ca2+ ATPases with plasma membrane distribution and high affinity for Ca2+, indicating that they are Ca2+ extrusion pumps. However, the data indicate that tissue-specific differences exist within this class, with the enzyme from adipocytes and rat corpus luteum belonging to a subclass in which the requirement for Mg2+ and any response to calmodulin are difficult to demonstrate.

Inhibition by putrescine of the induction of epidermal ornithine decarboxylase activity and tumor promotion caused by 12-O-tetradecanoylphorbol-13-acetate

The induction of epidermal ornithine decarboxylase (EC 4.1.1.17) (ODC) following topical application of the tumor-promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA) to mice can be inhibited by topical application of putrescine, the product of the enzyme. The degree of inhibition depended on both the dose and the time of putrescine application; application of 20 mumol of putrescine 2 hr after TPA treatment inhibited the induction of ODC activity by 50%. TPA-induced activity of another polyamine-biosynthetic enzyme, S-adenosyl-L-methionine decarboxylase (EC 4.1.1.50), was unaffected by application of putrescine. Among several amines tested for their ability to inhibit the induction of ODC activity, spermidine, 1,7-diaminoheptane, and spermine were the most effective, causing a 90% inhibition at the 20-mumol dose. Putrescine, when added directly to the assay medium at a 100-mumol dose level inhibited by 97% the TPA-induced ODC activity, but the amount of putrescine (20 mumol) which gave 50% inhibition of the induction of ODC activity in vivo had no effect when added to the assay system. Mixing of soluble extracts from TPA-treated mouse epidermis posttreated either with acetone or putrescine or with mouse epidermis treated with putrescine alone gave essentially additive ODC activity. Furthermore, putrescine did not elicit production of detectable ODC-antizyme activity in mouse epidermis. Putrescine inhibited the formation of mouse skin papillomas promoted with TPA. Topical application of 20 and 100 mumol of putrescine 2 hr after each application of TPA to mice initiated with 7,12-dimethylbenz[a]anthracene resulted in a 30 and 80% inhibition, respectively, of papilloma formation compared to animals receiving no putrescine.

Induction of mouse epidermal ornithine decarboxylase activity and skin tumors by 7,12-dimethylben

Application of a single large dose (3.6 micromol) or smaller weekly repeated doses (0.2 micromol) of 7,12-dimethylbenz[a]anthracene (DMBA) to the skin of CD-1 mice led to a 20 to 50-fold increase in epidermal ornithine decarboxylase (ODC) (EC 4.1.1.17) activity as well as tumor formation. Retinoic acid (0.17-68 nmol), a potent inhibitor of both the induction of ODC activity and tumor formation by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), failed to inhibit both the induction of ODC activity and tumor formation by DMBA. In contrast, 7,8-benzoflavone (367 nmol), which did not inhibit the induction of ODC activity by TPA, effectively inhibited the induction of ODC activity as well as the formation of skin tumors caused by DMBA. These results indicate that (a) the mechanism of the induction of ODC activity and tumor formation by a complete carcinogen appears to be different from that of the tumor promoter TPA, (b) DMBA-induced ODC activity may be an important component of the mechanism of DMBA carcinogenesis, and (c) the protective effect of retinoic acid on skin carcinogenesis is not universal; it inhibits skin tumor formation by some agents and not by others.

Inhibition of skin tumor promotion by retinoic acid and its metabolite 5,6-epoxyretinoic acid

The ability of 5,6-epoxyretinoic acid, a biologically active metabolites of retinoic acid, to inhibit both the induction of ornithine decarboxylase (ODC) activity and skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA) was evaluated. Application of 5,6-epoxyretinoic acid either concurrently with or 1 hr after each application of TPA to the initiated mouse skin inhibited the formation of skin tumors as effectively as did retinoic acid. 5,6-Dihydroretinoic acid, which is a poor substrate for epoxidation, also inhibited skin tumor promotion. 5,6-Epoxyretinoic acid, 5,6-dihydroretinoic acid, and retinoic acid were equally effective in inhibiting the induction of ODC activity by TPA. Insect juvenile hormones inhibited neither the induction of ODC activity nor skin tumor promotion by TPA. These results indicate that (a) epoxidation of retinoic acid at the 5,6-position is not a rate-limiting modification for the anti-promoting activity of retinoic acid and that (b) inhibition of the induction by TPA of mouse epidermal ODC activity may be a simple test for screening the potential prophylactic activities of new retinoids.