Rf values of different width filter paper chromatograms using 75 per cent methanol in an ascending system are presented for iodide and iodate. The chemical identity of the spots is determined by the use of carrier iodide and iodate. The iodide spot was developed by spraying the dry chromatogram with starch hydrogen peroxide solution. The iodate spot was developed with a spray of ascorbic acid‐starch solution. Description of the equipment is given. The relationship of the chart drive speed and the optimal slit width to the time constant of the counting rate meter is discussed and the minimal slit width calculated for the instrument used. Integration of the curves gave areas representing the total activity at each spot. The ratio of the iodide‐iodate activities thus determined differed from the relative readings of the counting rate meter.

The calibration of I131 using the electroscope, the method of absolute beta counting, and the method of the simulated I131 reference source is reported. The characterization of the beta radiation of I131 through the determination of the mass absorption coefficient in aluminum is described. A test for the radiochemical purity is given.

A brief review of some of the applications of radioactive isotopes to pharmaceutical research is presented. Subsequent reports will describe experimental procedures and include data on the application of radioactive isotopes to research.

This study evaluated the differences in toxicity and tissue distribution for 16 groups of male rats repeatedly exposed to 100 ppm of 14CCl4 vapors for 8 or 11.5 hr/day for periods of 1 to 10 days. Serum sorbitol dehydrogenase (SDH) was also evaluated for its sensitivity at detecting CCl4-induced hepatotoxicity. Following 1, 2, 3, 4, 5, 7, 11, and 14 days, one group of rats from each exposure schedule was sacrificed and 14C activity in seven tissues and serum SDH levels were measured. To compare the effects of CCl4 on the liver and kidney following repeated exposure to the two schedules, one group of rats was exposed for 8 hr/day for 10 of 12 consecutive days and another for 11.5 hr/day for 7 of 12 consecutive days so that each group received essentially the same dose (8000 ppm-hr) of CCl4. The 11.5-hr/day exposure schedule, compared to rats exposed 8-hr/day, produced minor changes in the distribution and concentration of 14C (CCl4 equivalents) in various tissues. Following 1 and 2 weeks of exposure to either schedule, the fat, liver, lungs, and adrenals had the highest concentration of CCl4 equivalents. There were no significant differences in CCl4-induced hepatotoxicity or nephrotoxicity between rats exposed to the two schedules following either 1 or 2 weeks of exposure as measured by histopathology. In contrast, rats exposed 11.5 hr/day had significantly higher SDH levels than those exposed to the 8-hr/day schedule; thus suggesting that the 11.5-hr schedule did produce a measurably greater degree of hepatotoxicity, although it was too subtle to detect pathologically. Rats exposed for a fourth and fifth day during the second week of the 11.5-hr schedule had a significantly greater concentration of 14C activity in the fat than rats exposed to the 8-hr/day schedule as well as severe fatty infiltration of the liver and higher serum SDH activity. This study demonstrated that SDH is a very useful assay for detecting subtle changes in liver injury as compared to histopathology. It was also shown that even at relatively low vapor concentrations, modest changes in dosage regimen, like those involving unusual (e.g., 10- or 12-hr/day) work schedules, can have a measurable effect on the distribution of the chemical and the degree of toxicity. These results support published recommendations which suggest that for persons working long shifts, occupational exposure limits for systemic toxicants with half-lives between 4 and 200 hr be reduced so that these persons will have the same margin of safety from any adverse effects.

The hepatotoxic properties of concurrent chronic oral ethanol ingestion and acute toluene inhalation were evaluated. Male rats were maintained on ethanol-containing or control liquid diets for 29 days. Animals of each group were subjected to five 20-min exposures to 10 000 ppm toluene with 30 min of room air inhalation between exposures on days 22, 24, 26, and 28 of liquid diet feeding. Some of the ethanol-fed animals were withdrawn from ethanol 14 h before exposure. Ethanol-withdrawn animals displayed an increased sensitivity to the narcotic action of toluene. Animals were sacrificed and assays performed on day 29. Stress markers (plasma corticosterone, free fatty acid, and glucose) were not affected by treatments. A modest elevation in plasma aspartate aminotransferase occurred in non-withdrawn animals receiving both ethanol and toluene. Ethanol-toluene exposure increased both relative liver weight and liver triglycerides. Toluene antagonized the hypertriglyceridemia associated with chronic ethanol ingestion. This study indicates that combined ethanol and toluene exposure has minor potential to induce acute liver injury, but results in altered deposition of hepatic triglycerides.

Tests for evaluating the hazard of inhalation exposure generally require large quantities of the chemical of interest. This paper describes an inhalation technique that involves a dynamic closed-loop recirculating system which uses only small amounts of toxicant since the test atmosphere to which the animals are exposed is recycled. Carbon dioxide and water are continually removed while the oxygen and test substance absorbed by the animals are replenished. The approach described is different from other closed-loop chambers since the test substance is continuously added to the chamber and the air concentration is continuously measured. The technique was successfully used to expose 20 adult rats for up to 12 consecutive hours to 100 ppm of 14C-carbon tetrachloride yet only 2-3 mL of test material were consumed. The inhalation chambers were fabricated from standard 40-liter cylindrical glass bell jars. A high number of air changes (35-40 equivalent chamber volumes per hour) permitted exposure of as many as five adult rats per 10 liters of chamber volume. This closed-loop approach should prove to be especially useful for evaluating the risk of exposure to very expensive materials or when only limited quantities of a test material are available. These systems may also be used to expose rats and other small animals to radioisotopes in studies which evaluate the uptake, distribution, metabolism, and excretion of volatile xenobiotics.

Hydrolyzed polyacrylonitrile grafted cellulose with a 14C label was synthesized by using 1−14C-acrylonitrile. The similarity of the labeled product to a commercial product was established by determining water retention values. The labeled product was administered orally to rats. Examination of respired carbon dioxide, urine, various tissues, and feces for 14C activity indicated that the labeled product was not metabolized but was excreted in the feces.

The concentrations of 36Cl-labeled potassium perchlorate (K36ClO4) and previously reported iodide (131I) in the ova, thyroid gland, and blood of the laying hen were compared in this investigation. Radioperchlorate concentration and deposition properties showed a remarkable resemblance to those of iodide (131I). The topographic distribution of radioperchlorate in ova followed a peripheral and concentric ring deposition identical to that observed in the 131I investigation. The studies of the distribution of radioperchlorate showed that about 10.3, 2.0, and 1.4% of a single intramuscular injection of K36ClO4 was retained in the body at 3, 24, and 48 hours, respectively. The largest total concentration in the 3-hour group was found in the blood (2.9%), followed by muscles (2.4%), internal organs (1.1%), and the 10 largest ova (1.0%). The 24 and 48-hour hens’ ova showed the largest concentrations with values of 1.5 and 1.2% of the dose, respectively. This represented 76.9 and 81.3% of the total activity retained in the body at these times. The excreta in the 3 and 24-hour experiments accounted for most of the radioperchlorate dose.

Exposure to 125I-labeled 2,3,5-triiodobenzoic acid resulted in deposition of the material in the lungs of rats. The initial uptake was 20.85% followed by removal at an exponential rate. The residency half-life in the lungs was 17.7 min. Exposure of animals to sulfur dioxide for 4 consecutive days, 4 hr/day, prior to inhalation of the labeled compound did not provide statistically significant differences in the parameters studied.

TLC and liquid scintillation spectrometry were used to determine the identities and relative quantities of aspirin and its metabolites in the gastric juice, blood plasma, rumen (non- glandular portion), and corpus (glandular portion) of the rat stomach 4min. after the oral administration of aspirin-7-14C. It was found that aspirin and salicylic acid are the major components in the gastric juice, blood plasma, and rumen and corpus tissues. Trace levels of a compound with an Rce_ value corresponding to that of salicyluric acid was found in the fluids and tissues analyzed. No glucuronide conjugates of salicylic acid or polyhy- droxy metabolites of aspirin were found. The level of salicylic acid was fourfold higher in the corpus tissue than in the rumen tissue.

A study using 14C-labeled chlorophenothane was statistically designed to evaluate the effect of five treatments (cold, fasting, levarterenol bitartrate, prediphenylhydantoin, and post- diphenylhydantoin) upon the fecal elimination of the pesticide from rats. To 24-hr.-fasted rats, 7 μc. of 14C-chlorophcnothane was administered intraperitoneally. The pesticide was allowed to distribute into the tissues of the animals for 5 days prior to initiation of the treatments which were continued for 3 days. The cold group was kept at 2-4°. The fasted rats were deprived of food but had water ad libitum. Levarterenol bitartrate and diphenylhydantoin were administered twice a day at 1.0 and 75.0 mg./kg. body weight, respectively. Diphenylhydantoin was administered before chlorophenothane (prediphenylhydantoin) to one group of rats and after administration of the pesticide (postdiphenylhydantoin) to a second group. The 14C-activity in the feces was measured by liquid scintillation. Thirty-six rats were assigned in a randomized complete block design of three replicates with two rats per treatment, five treatments, and a control per replicate. Homogeneity of variance tests indicated that the variances between rats were homogeneous. Two- way analysis of variance tests showed that replicates could be pooled and the data reanalyzed as if a completely randomized design were run. Hence, a one-way analysis of variance and the Newman-Keuls sequential range tests were performed. The latter tested for significant differences between all pairs of treatments. The statistical design allowed for minimum expenditure of animals and radioisotope and provided reliable data. Cold treatment was the only treatment that increased the fecal elimination of chlorophenothane. Prcadministration of diphenylhydantoin may have stimulated hepatic enzymes to alter deposition and increase apparent elimination of chlorophenothane.

14C-Labeled chlorophenothane was acutely administered orally and intraperitoneally to rats to study the tissue distribution, rate of excretion, and effect of the route of administration. Five days after dosing, the fat was the tissue with the highest radioactivity irrespective of the route of administration. At the 0.05 significance level, the lungs, spleen, liver, kidneys, and testes of intraperitoneally dosed rats showed greater concentration than those orally dosed. The fecal excretion of the latter group was higher than those of the former group. The greatest percentage of radioactivity excreted in feces after oral administration occurred in the first 24 hr. Urinary excretion by the two routes was statistically the same. Negligible 14CO2 was detected in the respired air. The results of this experiment support previously reported nonradiotracer studies.

The excretion and tissue distribution of pentachlorophenol were studied in rats by administration of oral doses of 99.5% radiochemically pure, uniformly labeled 14C-pentachlorophenol dissolved in olive oil. After oral administration, less than 0.04% of the administered radioactivity was detected in the respired air in a 24-hr. period. The recovery of pentachlorophenol and/or metabolites in the urine was greatest at the 16-hr. collection period. The average total percent of the administered activity recovered in the urine after 24hr. was 50.2%, with between 9.2 and 13.2% being recovered in the feces after 10 days. The tissues containing the highest levels of activity were the liver, kidney, and blood, respectively. All other tissues contained less activity than the blood.

The chromatographic behavior of DDT and fourteen related compounds, metabolites, analogs, and degradation products on commercially available pre-coated aluminum oxide thin-layer chromatoplates was investigated using thirty-three solvent systems. The color and/or fluorescence response of the DDT-type compounds and their sensitivity to a chromogenic reagent consisting of ammoniacal silver nitrate and 2-phenoxyethanol in acetone is discussed. A total of eleven compounds of the mixture were separated by two-dimensional thin-layer chromatography on aluminum oxide plates.