Metabolism of small multiple doses of (14C) nicotine in the cat

Effects of nicotine administration in a mouse model of familial hypertrophic cardiomyopathy, α-tropomyosin D175N

The effects of nicotine (NIC) on normal hearts are fairly well established, yet its effects on hearts displaying familial hypertrophic cardiomyopathy have not been tested. We studied both the acute and chronic effects of NIC on a transgenic (TG) mouse model of FHC caused by a mutation in α-tropomyosin (Tm; i.e., α-Tm D175N TG, or Tm175). For acute effects, intravenously injected NIC increased heart rate, left ventricular (LV) pressure, and the maximal rate of LV pressure increase (+dP/dt) in non-TG (NTG) and Tm175 mice; however, Tm175 showed a significantly smaller increase in the maximal rate of LV pressure decrease (-dP/dt) compared with NTGs. Western blots revealed phosphorylation of phospholamban Ser16 and Thr17 residue increased in NTG mice following NIC injection but not in Tm175 mice. In contrast, phosphorylation of troponin I at serine residues 23 and 24 increased equally in both NTG and Tm175. Thus the attenuated increase in relaxation in Tm175 mice following acute NIC appears to result primarily from attenuated phospholamban phosphorylation. Chronic NIC administration (equivalent to smoking 2 packs of cigarettes/day for 4 mo) also increased +dP/dt in NTG and Tm175 mice compared with chronic saline. However, chronic NIC had little effect on heart rate, LV pressure, -dP/dt, LV wall and chamber dimensions, or collagen content for either group of mice.

Urinary biomarkers to assess exposure of cats to environmental tobacco smoke

OBJECTIVE

To evaluate the use of urinary biomarkers to assess exposure of cats to environmental tobacco smoke (ETS).

ANIMALS

61 healthy client-owned cats (19 from households in which smoking was reported and 42 from households in which there was no smoking).

PROCEDURES

Urine samples were obtained from each cat and assayed for total nicotine (nicotine plus nicotine glucuronide) and total cotinine (cotinine plus cotinine glucuronide) content by use of gas chromatography-mass spectrometry. In addition, total urinary content of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a major metabolite of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, was measured by use of gas chromatography with nitrosamine-selective detection.

RESULTS

Cats from households in which smoking was reported had significantly higher concentrations of total nicotine (70.4 ng/mL), total cotinine (8.53 ng/mL), and total NNAL (0.0562 pmol/mL) in urine, compared with concentrations for cats that lived in households in which there was no smoking (4.89 ng/mL, 0.74 ng/mL, and 0.0182 pmol/mL, respectively).

CONCLUSIONS AND CLINICAL RELEVANCE

Analysis of these data provided biochemical evidence of exposure to ETS and uptake of tobacco-specific carcinogens by cats that live in households with smokers. Biomarkers could facilitate investigation of the health effects of ETS in cats and other species.

Neuropharmacological effects of nicotine in relation to cholinergic mechanisms

Studies with nicotine have, from the outset, been of fundamental importance for the elucidation of physiological mechanisms. However, many nicotinic cholinoreceptors do not appear to subserve a physiological role, at least within the present framework of knowledge. The main challenge in the immediate future is to determine the functional role of nicotinic cholinoceptors in the CNS. This knowledge will not only add to the physiological mechanisms that have been unravelled as a result of studies with nicotine, but will also provide a major contribution to the understanding of tobacco use.

Influence of kinetics of nicotine administration on tolerance development and receptor levels

Nicotine was administered intravenously to DBA mice through cannulae implanted in the jugular veins. Five groups of animals were treated: a control group which received saline and four nicotine treatment groups. All of the nicotine treatment groups received a dose of 4.0 mg/kg/hr. The first group received continuous infusion, the second group received 1 mg/kg pulses four times an hour, the third group received 2 mg/kg pulses twice an hour, and the fourth group received 4 mg/kg pulses once an hour. After a 10-day treatment period, the animals were tested for tolerance to an acute intraperitoneal administration of nicotine. Tolerance was measured using a test battery composed of the following tests: respiratory rate, acoustic startle response, Y-maze crosses and rears, heart rate, and body temperature. Mice from each of the four nicotine treatment groups were tolerant to the acute effect of nicotine, but the extent of tolerance varied among the groups as follows: continuous infusion less than 1 mg/kg pulses four times/hr less than 2 mg/kg pulses twice/hr less than 4 mg/kg pulse once/hr. Chronic nicotine infusion resulted in significant increases in the binding of L-[3H]nicotine in all six brain regions assayed and in significant increases in the binding of alpha-[125I]bungarotoxin binding in cerebral cortex and hippocampus. All increases in binding resulted from increases in Bmax for these ligands. In contrast to the effects observed for tolerance development, the increases in [3H]nicotine binding were not significantly affected by the kinetics of nicotine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Nicotine antibodies: comparison of ligand specificities of antibodies produced against two nicotine conjugates

Conjugates between bovine serum albumin and (R,S)-2-aminonicotine were produced, and these conjugates were employed in rabbits and goats for the production of nicotine antibodies. In the assay of nicotine, an 125I-tyrosine methyl ester derivative of (R,S)-6-aminonicotine was employed as radioligand. The antibody-bound derivative was separated from the free derivative by charcoal adsorption (0.5% charcoal, 0.1% dextran T-70, 0.1% bovine serum albumin pH 7.3). Among the twenty five nicotine derivatives and metabolites examined, (R,S)-6-aminonicotine gave the highest cross-reaction. Cross-reaction with cotinine, a major mammalian metabolite of nicotine, was less than 0.1% for both the rabbit-derived and goat-derived antisera. Cross-reaction by other metabolites, such as (S)-nicotine-N'-oxide, (S)-nornicotine, and N-methylpyrrolidine was less than 1%. The antibodies produced were thus highly specific to nicotine. The radioimmunoassay for nicotine showed a maximum sensitivity of 10 ng/ml in 50-microliter plasma samples for both antisera. After the smoking of a single cigarette (1.2 mg nicotine content in mainstream) the peak of blood plasma level of nicotine in the subjects varied from 20--104 ng/ml, and high levels of nicotine were not necessarily found in heavy smokers.

Nicotine in breast fluid of nonlactating women

Using a combination of gas chromatography, mass spectrometry, and selected ion recording techniques, we have identified nicotine and its major metabolite, continine, in the breast fluid of nonlactating women smokers. As little as 25 picograms could be measured by using the deuterated variants, [5',5'-2H]nicotine and [3,3-2H]cotinine, both as internal standards and as carriers in an inverse isotope dilution method.

Absorption and metabolism of nicotine from cigarettes

Eight men volunteers each smoked a single cirgarette containing 14C-nicotine and gave arterial blood samples during and for 50 minutes after smoking. The maximum concentration of nicotine in the arterial blood ranged from 31 to 41 mug/l in four regular cigarette smokers who inhaled. Two non-smokers achieved maximum levels of 2 and 4 mug/l. On a separate occasion two of the inhalers received 1 mg. 14C-nicotine in 10 divided doses injected intravenously. In both cases the peak arterial nicotine concentrations bore a similar relationship to the intravenous dose, as did the peak nicotine concentrations to the retained doses during smoking.

Influence of route of administration on metabolism of [14C]nicotine in four species

1. The metabolism of [14C]nicotine has been studied in four species of animals, rabbit, rat, cat and squirrel monkey, after administration by different routes. 2. Intravenous injection of 4 mug/kg [14C]nicotine every 60 s for 1 h results in peak blood levels of approximately 100 ng/ml in all species but the rabbit. [14C]Cotinine levels in blood vary widely between species. 3. Subcutaneous injection of 0.4 mg/kg [14C]nicotine produces similar peak blood nicotine levels but the time course, for a given species, is different. 4. Intragastric instillation of 1 mg/kg [14C]nicotine to the cat and rabbit results in much lower levels of [14C]nicotine in blood and relatively high levels of [14C]cotinine. 5. Urinary excretion data indicate that, irrespective of route, the squirrel monkey excretes only a small proportion of the dose into urine during the period of experiment, of which the major proportion is [14C]nicotine. The cat, in contrast, excretes a relatively large proportion of the dose during the experimental period though only a minor proportion of the radioactivity is due to [14C]nicotine or [14C]cotinine. 6. All four species are potentially useful for model experiments with nicotine, though metabolism of nicotine by squirrel monkey is most similar to man.

Nicotine-induced hypophagia and hypodipsia in deprived and in hypothalamically stimulated rats

Nicotine, in doses of 0.15 and 0.45 mg/kg, induced hypophagia and hypodipsia in 20 hrs-deprived rats and elevated the threshold currents for hypothalamically induced feeding and drinking in satiated rats. These effects were blocked by pretreatment with 0.5 mg/kg mecamylamine, but not by pretreatment with 3.0 or 9.0 mg/kg hexamethonium. These results indicate a centrally-located mechanism for the hypophagic and hypodipsic effect of single injections of nicotine.