Role of protein kinase C in catecholamine secretion from digitonin-permeabilized bovine adrenal medullary cells.

The effects of staurosporine and K-252a, potent inhibitors of protein kinases, and 12-O-tetradecanoylphorbol-13-acetate (TPA) on catecholamine secretion and protein phosphorylation in digitonin-permeabilized bovine adrenal medullary cells were investigated. Staurosporine and K-252a (0.01-10 microM) did not cause large changes in catecholamine secretion evoked by Ca2+ in digitonin-permeabilized cells whereas these compounds strongly prevented TPA-induced enhancement of catecholamine secretion in a concentration-dependent manner. Incubation of digitonin-permeabilized cells with [gamma-32P]ATP resulted in 32Pi incorporation into a large number of proteins, detected as several major bands and darkened background in autoradiograms. Ca2+ and TPA increased phosphorylation of these proteins. Staurosporine and K-252a markedly inhibited Ca(2+)-induced and TPA-induced increases in protein phosphorylation as well as basal (0 Ca2+) protein phosphorylation in digitonin-permeabilized cells. Long term treatment (24 h) of adrenal medullary cells with 1 microM TPA markedly decreased total cellular protein kinase C activity to about 5.3% of control. Pretreatment of the cells with 1 microM TPA strongly inhibited the TPA-induced enhancement of catecholamine secretion whereas it did not cause large changes in total cellular catecholamine amounts, Ca(2+)-induced catecholamine secretion, and cAMP-induced enhancement of catecholamine secretion from digitonin-permeabilized cells. From these results we conclude that protein kinase C plays a modulatory role in catecholamine secretion rather than being essential for initiating catecholamine secretion.

Vascular effects of isosorbide dinitrate on the common carotid artery in human volunteers.

The effects of 20 mg of orally administered isosorbide dinitrate (ISDN, Isocoronal R; CAS 87-33-2) on cerebral hemodynamics were investigated in 14 normal healthy volunteers (average age 32.6 years). The common carotid artery hemodynamics in the right supraclavicular region were measured using an ultrasonic quantitative flow measurement system. 2 h after drug administration, systolic blood pressure (15.5 mmHg, p less than 0.001) and mean blood pressure (7.2 mmHg, p less than 0.02) decreased significantly, but diastolic blood pressure did not change. A decrease in blood flow volume (2.85 ml/s, p less than 0.001) and blood flow velocity (7.00 cm/s, p less than 0.001), and an increase in mean vessel diameter (0.19 mm, p less than 0.05), and volume elasticity (0.68 x 10(5) dyn/cm2, p less than 0.02) were observed with ISDN. Mean vessel diameter increased gradually and reached its maximum at 4 h. However, the other maximal effects of ISDN were exerted at about 2 h. The ultrasonic quantitative flow measurement system was found to be useful in the case of repetitive measurements of the common carotid artery hemodynamics. It has been demonstrated that ISDN (20 mg/subject, p.o.) increases the diameter of the common carotid artery, although it decreases the blood flow in the common carotid artery.

Alpha 4 is a major acetylcholine binding subunit of cholinergic ligand affinity-purified nicotinic acetylcholine receptor from rat brains.

Nicotinic acetylcholine receptor (nAChR) purified from rat brains by cholinergic ligand affinity chromatography was characterized. Monoclonal antibody 299, which binds an acetylcholine (ACh) binding subunit termed alpha 4, depleted more than 85% of [3H]ACh binding activity of the purified preparation. A number of cholinergic agonists strongly inhibited [3H]ACh binding to the purified nAChR, whereas potential antagonists were less effective than the agonists. These results show that most of the purified nAChR contains alpha 4 subunit and the pharmacological properties are preserved upon purification.

Affinity purification of nicotinic acetylcholine receptor from rat brain.

Using chromatography on DE-52 and acetylcholine-Affi-Gel columns, nicotinic acetylcholine receptor was purified to approximately 10,000 fold from Lubrol extract of rat brain with a recovery of 15%. The purified preparation contained no cholinesterase activity. alpha-Bungarotoxin did not inhibit [3H]acetylcholine binding to the purified preparation. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed 4 major protein bands with apparent molecular weights of 53,000, 67,000, 80,000 and 108,000. When nicotinic acetylcholine receptor was eluted with either carbachol or nicotine from the affinity column, these major bands were found on SDS-PAGE gels. Immunoblot analysis showed that the Mr 80,000 protein was an acetylcholine-binding subunit and that the Mr 48,000 protein, a minor band on SDS-PAGE gel, was a structural subunit.

Effects of nicotine on ambulatory activity in mice.

Nicotine (0.5 and 1.0 mg/kg) administered subcutaneously to mice decreased the ambulatory activity recorded by an ambulo-meter in a dose-dependent manner from 5 to 60 min after the administration, and the higher dose (1.0 mg/kg) caused a long-lasting ataxia. To be noted was the initial increment of ambulation which usually preceded the ataxia-inducing effect with every dose of nicotine, and the lowest dose (0.10 mg/kg) employed herein induced only the increasing effect on ambulation recorded for the first 20 min after its administration. The ataxia-inducing effect of nicotine (1.0 mg/kg) was attenuated by the pretreatment with mecamylamine (0.4-2.0 mg/kg) in a dose-dependent manner, though the attenuating effect waned at a higher dose (4.0 mg/kg). In contrast, pretreatment with either hexamethonium (2.5 and 5.0 mg/kg) or atropine (1.0, 2.5 and 5.0 mg/kg) did not affect the ataxia-inducing effect of nicotine. Atropine when administered alone was found to markedly increase the ambulatory activity at the doses used for the pretreatment. Measurement of the time-dependent change of [3H]-nicotine level in brain tissue after its subcutaneous injection revealed that there is a good correlation between the brain levels of the alkaloid and the intensity of its ataxic effect rather than the initial increasing effect on ambulation. The results obtained herein suggest that nicotine exerts its ataxic effect centrally, but the site and type of the receptor stimulated by nicotine remains to be identified.

Formation of two major nicotine metabolites in livers of guinea pigs.

Using antibody against NADPH-cytochrome P-450 reductase and several effectors of cytochrome P-450 and FAD-containing monooxygenase, we investigated nicotine metabolites formed by these two enzymes. When [3H]nicotine was metabolized by the combination of liver microsomes of guinea pigs and partially purified aldehyde oxidase, three distinct spots corresponding to nicotine, cotinine and nicotine-1'-oxide were observed on fluorograms of thin-layer chromatography. Antibody against NADPH-cytochrome P-450 reductase inhibited the formation of cotinine but not nicotine-1'-oxide. Metyrapone and n-octylamine inhibited the cotinine formation, while methimazole prevented the formation of nicotine-1'-oxide. These results show that microsomal electron transport systems participate in the formation of nicotine-1'-oxide and strongly suggest the involvement of FAD-containing monooxygenase in the formation of nicotine-1'-oxide.

Determination of 15NH3 by gas chromatography-mass spectrometry. Application to the measurement of putrescine oxidation by human plasma.

A convenient and sensitive method for the determination of 15NH3 has been developed. Ammonia was purified from sample solutions by a modified microdiffusion method, derivatized with pentafluorobenzoyl chloride to pentafluorobenzamide (PFBA) and determined by gas chromatography-mass spectrometry using a multiple ion detector. PFBA was eluted from the gas chromatographic column within 2 min and resulted in a simple mass fragmentation pattern. The 15N/14N ratio was accurately determined with picomole amounts of PFBA by measuring the molecular ions of PFBA and [15N]PFBA. The method was applied to the assay of putrescine oxidation by human plasma. 15NH3 was produced by incubating 15N-labelled putrescine with plasma. The 15NH3 production was time dependent and strongly inhibited by the addition of aminoguanidine, an inhibitor of diamine oxidase. Exceedingly high 15NH3 production from [15N]putrescine was observed in the plasma from pregnant women. In contrast, only trace amounts of 15NH3 were formed in the plasma from normal men and non-pregnant women. The method seems to be applicable to various biological systems that produce ammonia as a metabolic product.

Distribution and Metabolism of sym-Homospermidine and Canavalmine in the Sword Bean Canavalia gladiata cv Shironata.

The unusual polyamines, sym-homospermidine (homoSPD) and canavalmine (CAN), were found in the seed of Canavalia species such as C. gladiata, C. ensiformis, and C. brasilensis, but not in those of other leguminous crops. To examine the distribution and metabolism of homoSPD and CAN in sword bean, C. gladiata cv Shironata, polyamine analysis was carried out throughout the life cycle of this plant. During seed germination, putrescine (PUT), spermidine (SPD), and spermine (SPM) were accumulated in the radicle and hypocotyl. HomoSPD and CAN were, however, maintained at very low levels over a 6-day period of germination. In nodulated sword bean plants, a large quantity of homoSPD was found in the root nodule. CAN was detected exclusively in the senescent nodule at very low concentrations. These polyamines were not detected in any other organs including root, stem, leaf, vine, flower, and pod, while PUT, SPD, and SPM were always found in those organs. As plants reached the reproductive stage, homoSPD and CAN appeared in the immature seed and their concentrations increased as seed formation progressed. By contrast, the level of SPM continuously decreased during seed development. In developing seeds, considerable accumulation of canavanine, an analog of arginine, which is a precursor in polyamine biosynthesis, was also observed.

Circadian variation of nicotine-induced ambulatory activity in rats.

Circadian variation of nicotine-induced ambulatory activity in drug-naive rats was investigated. To test ambulatory activity, male Wistar rats (4 weeks of age) housed under a 12 hr light-dark cycle (light on from 6:00 to 18:00) with dawn and dusk periods (each over 2 hr), for 25 days, were injected with nicotine (0.1 or 0.5 mg/kg) at one of six times each day (2:00, 6:00, 10:00, 14:00, 18:00 and 22:00). These activities were recorded with an Ambulo-meter for 120 min immediately after subcutaneous injection of nicotine or 0.9% NaCl solution (saline). A large dose of nicotine (0.5 mg/kg) depressed the ambulatory activity and induced ataxia during the first 20 min, but the activity increased later in the test session at all times of the day. On the other hand, a small dose of nicotine (0.1 mg/kg) depressed the activity and induced ataxia during the first 20 min except at 14:00, but the activity depended on the lapse of time after the injection at all times. In circadian variations which developed higher susceptibility to the nicotine-induced ambulatory activity during successive 20 min segments of the test session, administration of a large dose of nicotine resulted in two peaks of response, one occurring at 18:00 and another at 6:00, in the periods between 0-20 and 60-80 min after injection, but the peak of susceptibility occurred at 22:00 in the periods between 80-100 and 100-120 min after injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of oral administration of nicotine on circadian rhythms of ambulatory activity and drinking in rats.

Effects of nicotine on circadian rhythms of ambulatory activity and drinking in male Wistar rats were examined. Nicotine was administered through the drinking water, and the daily doses of nicotine were adjusted to 0.5, 5 and 20 mg/kg/day. The treatment of nicotine induced a dose-dependent increase in ambulatory activity. On the other hand, fluid intake decreased at a dose of 20 mg/kg/day. Although the ambulatory activity and drinking were influenced by a long-term oral administration of nicotine, their circadian patterns, which were characteristic of nocturnal animals, were not altered.

Erythroid differentiation of cultured murine erythroleukemia cells by the spermine analogue canavalmine.

Canavalmine, an analogue of spermine, induced erythroid differentiation of murine erythroleukemia cells 745A, as evidenced by benzidine staining and heme content of cultured cells. Benzidine-positive cells synthesizing hemoglobin appeared on day 4 after addition of 250 microM canavalmine. The canavalmine-induced cell differentiation was inhibited by the addition of agents which alter the structure of the cell membrane, such as local anesthetics (procainamide and lidocaine) or Ca2+ antagonists (nifedipine and verapamil) at dosages not toxic for the cell growth. Canavalmine did not significantly affect the levels of conjugated polyamines in the acid-insoluble fraction of the cells. In contrast, the level of free spermidine in the acid-soluble fraction greatly decreased during the 18 h after canavalmine treatment. Putrescine and spermidine, when added externally to the growth medium, showed dose-dependent inhibition of canavalmine-induced cell differentiation. Neither cadaverine nor spermine had any significant effect. These results suggest that not only structural change of cell membrane but alteration of the polyamine metabolism, especially a regulation of the cellular level of free spermidine, might have a key importance in erythroid differentiation of murine erythroleukemia cells induced by canavalmine.

[Influences of free intake of nicotine on several circadian rhythms in rats].

Male Wistar rats, aged 4 weeks, were kept in a temperature controlled room with a 12 hr light-dark cycle and given food and water ad libitum. The nicotine-treated group of rats was given water containing nicotine, which was estimated to be 10 mg/kg/day, for 40 days. Spontaneous motor activities, drinking activities and serum corticosterone levels showed circadian rhythms characteristic of a nocturnal animal in both the control and the nicotine-treated groups. As compared to the control group, however, the nicotine-treated group showed an increase in ambulatory activities, a decrease in drinking activities and a diminution of weight gain. In comparison with diurnal variations, serum corticosterone levels and liver nicotine oxidase activities increased in the nicotine-treated group during the dark period. However, the pattern of circadian rhythms characteristic of a nocturnal animal were not altered.

Cytochrome P-450-dependent nicotine oxidation by liver microsomes of guinea pigs. Immunochemical evidence with antibody against phenobarbital-inducible cytochrome P-450.

When guinea pigs were treated with phenobarbital (PB), the specific activity of liver microsomal nicotine oxidase increased by 42%. PB-inducible cytochrome P-450 (PB-P-450) was purified to homogeneity from liver microsomes of PB-treated guinea pigs. Purified PB-P-450 catalyzed nicotine oxidation when reconstituted with NADPH-P-450 reductase and phospholipid system. Antibody prepared against the purified PB-P-450 formed single precipitation lines with both purified PB-P-450 and microsomal components in livers of PB-treated guinea pigs, and both precipitation lines fused. The antibody against PB-P-450 strongly inhibited nicotine oxidation in the reconstituted system. The antibody also inhibited liver microsomal nicotine oxidase activities in PB-treated and untreated guinea pigs by about 30% and less than 5% respectively. About 45% of total P-450 in liver microsomes of PB-treated guinea pigs was precipitated by the antibody. These results show that PB-P-450 participates in liver microsomal nicotine oxidation in PB-treated guinea pigs but not in untreated control animals.

Effects of the spermine analogue canavalmine on proliferation of murine erythroleukemia cells in culture.

The effects of canavalmine, a structural analogue of spermine, were studied in cultured murine erythroleukemia cells 745A. Canavalmine exerted an inhibition on murine erythroleukemia cell growth at concentrations over 50 microM. The cell proliferation was, however, restored when canavalmine was removed from the culture medium after 24 h. Treatment of the cells with 500 microM canavalmine blocked the accumulation of intracellular polyamines. Especially, both spermine and spermidine levels were reduced below 50% of those in control cells after 48 h and below 30% after 96 h. The decreased contents of spermine and spermidine were compensated for by the increased content of canavalmine incorporated within the cells. In these cells, RNA and protein contents also decreased. The degree of growth inhibition by canavalmine during the cell cycle was examined using synchronized cells. Serum-induced growth stimulation was inhibited by canavalmine most effectively in the cells at G1 phase prior to DNA synthesis. The antiproliferative effect decreased when canavalmine was added to the cells after commencement of DNA synthesis. The results suggest that the growth-inhibitory action of canavalmine on murine erythroleukemia cells is most likely due to an inhibition of early events of the cell cycle, possibly due to the interference of a structure-specific function of spermidine and/or spermine on DNA replication.

Determination of polyamines in human blood by electron-capture gas-liquid chromatography.

The present work was undertaken to develop a sensitive and selective method for the estimation of putrescine, spermidine and spermine in human blood employing electron-capture gas--liquid chromatography. Polyamines were derivatized with heptafluorobutyric anhydride. The heptafluorobutyric derivatives of polyamines could be well resolved within 15 min under a temperature programme. The detection limit was 0.1 pmol for putrescine and cadaverine, and 0.02 pmol for spermidine and spermine. The method was applied to polyamine determinations in erythrocytes from human blood. For pre-separation of the polyamines from other compounds, a simple clean-up method utilizing an activated Permutit has been devised. Major interfering substances could be removed by the batchwise Permutit treatment. The mean values of spermidine and spermine concentrations, and the spermidine/spermine ratio in erythrocytes obtained from normal subjects (n = 11) were similar to reported values. The analytical procedure is thought to be applicable to various biological materials.

Hyperkalemia, hyperglycemia, and plasma levels of cyclic AMP and cyclic GMP induced by portal vein injection of cyclic nucleotides and their butyryl derivatives into dogs.

The levels of serum potassium, blood glucose, and plasma adenosine cyclic 3':5'-monophosphate (cAMP) and guanosine cyclic 3':5'-monophosphate (cGMP) were studied after the portal vein injection of cyclic nucleotides and their derivatives, (cAMP, cGMP, N6, O2'-dibutyryl adenosine 3':5'-monophosphate (DBcAMP), N6-monobutyryl adenosine cyclic 3':5'-monophosphate (NMBcAMP), and O2'-monobutyryl adenosine cyclic 3':5'-monophosphate (OMBcAMP), into dogs. Dose-related hyperglycemic responses were observed after the injection of DBcAMP (1-8 mg/kg). Transient and prominent hyperkalemia and hyperglycemia were caused by the injection of DBcAMP, NMBcAMP, and OMBcAMP (4 mg/kg). The hyperkalemic response was highest with NMBcAMP (1.22 mequiv./L), followed by OMBcAMP (0.64), DBcAMP (0.54), cGMP (0.47), and cAMP (0.41), whereas the hyperglycemic response was highest with NMBcAMP (146 mg/100 mL), followed by DBcAMP (93.6), OMBcAMP (77.1), and cAMP (56.0), and there was only a slight change with cGMP (28.4) compared with the control. The plasma level of cAMP was maximal with DBcAMP (1.92 nmol/mL), followed by NMBcAMP (1.28) and OMBcAMP (0.76), whereas the plasma levels of cGMP showed no evident change, except that caused by DBcAMP (0.27). Of the cyclic nucleotides tested, NMBcAMP was found to be most potent in causing both hyperkalemia and hyperglycemia. Based on these results, possible correlations between hyperkalemia, hyperglycemia, and plasma levels of cAMP and cGMP are discussed.