Carolyn Marlowe

Oral administration of nicotine: Its uptake and distribution after chronic administration to mice

An investigation was made of the suitability of administering nicotine to experimental animals by inclusion in the drinking water. It was found that, after an initial accommodation period of several weeks, nicotine could be administered up to a concentration of 100 micrograms/ml with no decrease in fluid intake or weight gain compared to control. An analysis of the steady-state plasma levels and distribution of nicotine was made in mice which had received nicotine in the drinking water at a concentration of 60 micrograms/ml. The average daily dose of nicotine received by these animals was 17.2 mg/kg. The steady-state plasma level of nicotine was 34.4 ng/ml, representing 6% of the total compound present at steady-state as determined by thin-layer chromatography. The distribution of nicotine or metabolite in mice which had received [methyl-14C]-nicotine orally was determined. Whole-body autoradiography, as well as direct tissue counting, demonstrated that nicotine accumulates in a number of areas, particularly the salivary gland, nasal epithelium, uterus, and liver. There was relatively little material in the blood or brain. This investigation indicates that ad libitum oral administration is an acceptable method for maintaining experimental animals on nicotine for long periods of time.

Tissue and cellular disposition of paraquat in mice

Abstract Male C57B1/6J mice were injected intravenously with [ methyl - 14 C]paraquat dichloride and frozen at 1, 3, 9, and 24 hr for whole-body autoradiography or with [ methyl - 3 H]paraquat dichloride and the lungs were removed at 3, 24, and 48 hr for cellular autoradiography. The methods do not allow thawing or exposure of the tissues to solvents; this prevents translocation or removal of radioactivity. The whole-body autoradiographs revealed localization of radioactivity at all time intervals in melanin, lung, choroid plexus, muscle, and excretory pathways such as proximal tubules of kidney, urine, liver, gallbladder, and intestinal contents. The radioactivity in lung was much higher in certain discrete, unidentified areas at all time intervals except at 1 hr. The concentration was high in myocardium at 1 and 3 hr. Cellular resolution autoradiography revealed that the radioactivity within the lung was confined almost entirely to cells having the distribution of alveolar type II cells at the three time intervals studied. The radioactivity in these cells was easily washed away indicating that an active transport process was probably involved instead of binding to a cellular constituent. The localization suggested that choline might be antidotal to paraquat toxicity. However, there was not a significant increase in survival of mice given 100 mg/kg choline chloride simultaneously to or following treatment with 50 mg/kg paraquat chloride.

The distribution of [14C]acrylamide in male and pregnant Swiss-Webster mice studied by whole-body autoradiography☆☆☆

Male and 13.5- and 17.5-day pregnant Swiss-Webster mice were administered 120 mg/kg [2,3-14C]acrylamide orally. The male mice were frozen 0.33, 1, 3, 9, 24, 72, and 216 hr later, and the pregnant mice at each gestational period were frozen at 3 and 24 hr. Whole-body autoradiographs from the male mice at early time intervals revealed accumulation of radioactivity in the contents of the gastrointestinal tract, liver, pancreas, testis, brain and gallbladder, and epithelia of oral cavity, esophagus, and bronchi. The distribution appears to be similar in the male and pregnant mice. Absorption from the stomach was virtually complete by 3 hr; renal and hepatic elimination was essentially complete at 24 hr. Radioactivity in the male reproductive tract appeared in the parenchyma of the testis at 1 hr, moved to the seminiferous tubules and head of the epididymis at 9 hr, and by 9 days remained only in the tail of the epididymis and the crypts of the epithelium of the glans penis. This movement parallels that of spermatids. The 13.5-day fetuses were uniformly labeled except for a slightly increased uptake in fetal brain. The distribution of radioactivity in the 17.5-day fetal tissues resembled that in maternal tissues; the remarkable exception was an intense accumulation in fetal skin. This study indicates that acrylamide is efficiently absorbed from the stomach and eliminated by the liver, kidney, and possibly the pancreas. A previously unrecognized affinity of acrylamide or a metabolic product was demonstrated for fetal skin in late gestation and for adult epithelia of oral cavity, esophagus, forestomach, and bronchi. Also, acrylamide or a metabolite appears to bind to spermatids at a specific stage near maturation.

Inhibition of the localization of urethane in mouse tissues by ethanol

[ethyl-1-14C]Urethane in water or in 12% ethanol was administered orally to male A/JAX mice and 1 hr later the mice were frozen and processed for whole-body autoradiography to identify sites of localization of radioactivity. When the [14C]urethane was administered in water, radioactivity was localized in the liver and bile, the salivary, seromucous and Harderian glands, the bone marrow and pancreas and the stomach and intestinal epithelia. When the labelled urethane was administered in 12% ethanol, localization of radioactivity in each of these sites was almost completely inhibited; radioactivity was still seen within the lumen of the stomach and intestine. Using a defined chemical system, no transesterification was observed between urethane and 12% aqueous [2H6]ethanol at pH 1.5 in 80 min. The inhibition of the localization of radioactivity in the tissues appears to be due most probably to blocking of the metabolism of urethane in tissues. This suggests that ethanol may inhibit the carcinogenicity of urethane in mice.

Autoradiographic disposition of [1-methyl-14C]- and [2-14C]caffeine in mice

Male, C57B1/6J mice received either [1-methyl-14C]caffeine or [2-14C]caffeine via the tail vein at a dose of 0.7 or 11 mg/kg, respectively. At 0.1, 0.33, 1, 3, 9, and 24 hr after treatment, the mice were anesthetized with ether and frozen by immersion in dry ice/hexane. The mice were processed for whole-body autoradiography by the Ullberg technique; this procedure does not allow thawing or contact with solvents. All autoradiographs revealed some retention of radioactivity at early time intervals in the lacrimal glands, seminal vesicle fluid, nasal and olfactory epithelium, and retinal melanocytes. The remaining portion of the animal was densitometrically uniform except for the lower levels noted in the CNS and adipose tissues. Excretion of radioactivity by the liver and kidneys seems to be the major routes of elimination. Localization in the liver at late time intervals was confined principally to the centrilobular region. Late sites of retention, observed only after [1-methyl-14C]caffeine administration, included the pancreas, minor and major salivary glands, splenic red pulp, thymal cortex, bone marrow, and gastrointestinal epithelium. Sites of localization present in both studies included the olfactory epithelium, lacrimal glands, hair follicles, and retinal melanocytes. Further studies are needed to determine whether the localization at these various sites is due to metabolic degradation, active transport, or possibly a specific receptor interaction.

Disposition of [14C]Dimercaptosuccinic Acid in Mice

Dimercaptosuccinic acid labeled with 14C ([14C]DMSA) was administered to mice iv; the mice were frozen by immersion in dry ice/hexane at 6 and 20 min and 1, 3, 9, and 24 hr after injection. The frozen mice were sectioned and processed for whole-body autoradiography for soluble substances. The radioactivity was highly localized in extracellular fluids such as the subcutaneous, intrapleural, intraperitoneal, and periosteal spaces. There was a pronounced accumulation in the periosteal fluid above that in other fluids during the first hour after injection. Most of the radioactivity was eliminated by the kidney and liver. Pretreatment of a mouse with HgCl2 subcutaneously 1 hr before [14C]DMSA produced an increase in radioactivity in the liver and decrease in lung. A high concentration of radioactivity was seen at the subcutaneous site of injection of the HgCl2. The results are interpreted to indicate that most of the DMSA is in the extracellular space but that it can cross cellular membranes to some extent. The pronounced accumulation in periosteal fluid may be an interaction of DMSA with Ca2+ in this space. No tissue had a pronounced retention of the compound, but lung retained more than most other tissues.

Affinity of [14C]nitrosopiperidine and metabolites for mouse epithelial tissues.

Male C57BL/6J mice were each administered iv 1.2 mg/kg (6.0 to 7.6 muCi) of [14C]nitrosopiperidine ([14C]NPIP) and frozen by immersion in dry ice/hexane at 0.1, 0.33, 1, 3, 9, and 24 hr after injection. The mice were processed for whole-body autoradiography without thawing or the use of any solvents; sagittal sections of the frozen mice were freeze-dried and placed on X-ray film to reveal areas of localization of radioactivity. The autoradiographs revealed intense localization of radioactivity at 6 min in the epithelium of the nose and bronchi, as well as in the liver, kidney, and salivary glands. There is virtually no affinity of [14C]NPIP for melanin. Most of the same localizations persisted from 6 min through 24 hr. At 24 hr the most intense accumulation was in the epithelium of the bronchi, nose, salivary gland ducts, and esophagus as well as the liver and Harders gland. The results are interpreted to suggest that at least one metabolite of NPIP which localizes in the sites where tumors occur may be similar to a metabolite of NNN. The distribution is consistent with metabolic conversion of [14C]NPIP in liver and epithelium of nose and bronchi with subsequent localization of the metabolite in epithelium of esophagus and salivary gland ducts.

The distribution of [14C]caprolactam in male, female and pregnant mice.

The distribution of [14C]caprolactam was studied by whole-body autoradiography in male, female and 14.5-day-pregnant mice. This technique does not allow translocation or removal of soluble compounds from the sites of localization. Pregnant mice were frozen 20 min and 1, 3, 9 and 24 hr after oral administration of the compound. The non-pregnant mouse was frozen 3 hr after oral dosing; two male mice were frozen 20 min and 9 hr after intravenous administration. Radioactivity was rapidly absorbed from the stomach and distributed throughout the entire animal, including the foetuses. There was efficient elimination by the kidney and liver. Material secreted by the liver into bile and intestinal contents appeared not to be reabsorbed via the enterohepatic circulation. The kinetics of distribution and elimination appeared to be the same in male, female and pregnant animals. The only sites of retention of radioactivity after 24 hr were the umbilical cords, amnion, yolk sac, maternal lens, maternal Harderian gland and maternal liver. The distribution into and removal from the foetuses was typical of molecules that diffuse freely across the placenta. There was no retention of radioactivity in any foetal tissue. With the possible exception of some residual activity in the nasal epithelium, no localization was seen that would suggest a site of toxic action of caprolactam.