A computer-assisted image analyzer system for the determination of tissue drug concentration using whole body autoradiograms is described. An image of a whole body autoradiogram was taken by the video camera, and the shading was corrected by the ratio correction procedure. Calibration curve was obtained by using standard tissue sections which contained known concentration of radioactivity. The non-linear relationship between mean gray values obtained by the video analysis method and radioactivity concentration in corresponding tissues was corrected by the linearization process. These correction procedures were effective to solve the problems of video camera-based image analysis of autoradiogram.
By using this video analysis method, indomethacin concentration in rat tissue after p.o. and i.v. administration was determined and was compared with that obtained by scintillation counting method. Both methods gave almost identical results in most of tissues, however, blood level of a drug affected the determination of its concentration in capillary rich tissues in the video analysis method.

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Previously, it was reported that guaiacol glycerol ether mononicotinate has an activity of lowering of cholestrerol level in plasma of rabbits and rats.
One of the metabolite, guaiacol glyceric acid ether, [B-(o-methoxyphenoxy) lactic acid] was isolated and also synthesized before.
In order to investigate whether this metabolite has hypocholesteremic action as well as the parent compound, the present work was performed.
First, the methods used for analysis of guaiacol glyceric acid ether are described.
Second, it was found that guaiacol glyceric acid ether, as one of the guaiacol glycerol ether metabolites, increased cholesterol excretion into rat urine especially when a mixitue of the compound and cholesterol was administered to rats.

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The relation between expiratory ¹⁴CO₂ pattern and dispositional partition of a ¹⁴C-carbonacious substrate following intravenous injection of tracer amount to rats was elucidated by radiorespirometic techniques. Two kinds of ¹⁴C-methionines and 4 kinds of ¹⁴C-glucoses labelled at different positions of their chemical structure were used for this purpose. In case of 2 kinds of ¹⁴C-methionines, [carboxyl-¹⁴C] and [methyl-¹⁴C]methionines, 2 different wave heights of the radiorespirometric patterns were recorded. However, no difference was observed in the wave heights and recovery rates of radioactivity among 4 kinds of ¹⁴C-glucoses, which stands completely against the conclusion reported by Dr. Wang. Results indicated that the wave height and recovery rates were responsible for the partition rate of ¹⁴C-atoms positioned on the substrate into carbon dioxide during their catabolism in vivo.

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Absorption, distribution and excretion of trazodone hydrochloride, a new antidepressant, after single and repeated oral administration in rats were studied using ¹⁴C-labelled drug (¹⁴C-trazodone hydrochloride). After single dose (4 mg/kg), the concentration of radioactivity in blood increased rapidly in male and female rats, suggesting rapid absorption of this drug. Similarly, tissue levels of radioactivity were immediately increased after the administration and declined thereafter without delay, which was consistent with the results of wholebody autoradiography. Urinary and fecal excretion during 96 hours was 38.6 and 60.1 % of total ingested radioactivity, respectively. At least 72.9 % of radioactivity excreted in bile was shown to be reabsorbed, which suggested significant contribution of enterohepatic circulation to time course of blood concentration. Concentration of radioactivity in the milk of lactating rats was slightly higher than that in the blood. Plasma protein binding of ¹⁴C-tradozone was shown to be constant within the concentration range studied in both in vitro and in vivo, although a large difference in fraction bound (88.7-89.9 % and 33.1-41.5 % for in vitro and in vivo, respectively) was found. After repeated oral dose (4 mg/kg/day), values of Cmax, AUC and T_1/2 in blood concentration and tissue levels of radioactivity tended to increase with increasing administration period. However, values of tissue-to-plasma concentration ratio and the minimum blood concentration after each administration had reached the steady-state after 14 th administration. Ratio of radioactivities excreted into urine and feces was not so much changed by multiple dosing.

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To study pharmacokinetics of magnetic resonance contrast agent, Gd-DTPA (Gadolinium-complex of diethylenetriaminepentaacetic acid), the method to determine the concentration of Gd-DTPA was established by using ICP (inductively-coupled plasma) emission spectrometry.
The emission intensity in creased linearly against the concentration of Gd-DTPA of more than 0.5 nmol/ml. There was no difference in the emission intensity between Gd-DTPA and GdCl₃.
For extraction of Gd-DTPA, tissue samples were digested at 150°C-180°C with HNO₃. About 0.1 g samples of dried tissues were optimal for digestion. Recovery of Gd-DTPA added to control liver was more than 90 % with excellent reproducibility, but at concentrations below 5 nmol the reproducibility was getting worse. From these findings, the detection limit was found to be 10 nmol/g wet tissue. Gd was not detected in any tissues of control rat.
The recovery of Gd-DTPA added to plasma was compared among three pretreatment methods (1. dilution method 2. digestion with HNO₃ 3. deproteinization by perchloric acid). The deproteinization method was the most appropriate in respect to the recovery and the operation. The detection limit in plasma was 2.5 nmol/ml.
In the tissues of rat, given Gd-¹⁴C-DTPA, the amount of Gd-DTPA measured by this assay method was almost consistent with that obtained by the radioactivity measurement.
Gd-DTPA in the tissues and the plasma of rat after intraveneous administration (2.5 mmol/kg) was determined by ICP analysis. Gd-DTPA rapidly disappeared from plasma within 6 hrs. In the liver, spleen and bone, Gd-DTPA almost completely disappeared within 14 days, but in the kidneys, 60 days were required for complete elimination.
In conclusion, ICP spectrometry can be adapted to pharmacokinetic study of Gd-DTPA.

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The relationship between photographic density with radioactivity of particle emitters and exposure period was studied for quantification of macroautoradiography.
Photographic density was recorded over 3 different types of X-ray high sensitive films with time by contacting with 7 different radioactivity sheets of autoradiographic standard kits, ¹⁴C-polymethacrylate.
A good correlation was obtained between radioactivity and photographic density for during a 2 or 3 day exposure period. There was also a good relationship between exposure period and photographic density in case of low radioactivity of 0.025-0.75 μCi/g in the sheets. This relationship was disturbed by unequivalent combination of the radioactivity and exposure period.
Discussion was presented to clarify the analysis of such a complex relations as mentioned above.

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Bermoprofen, 2-(8-methyl-10, 11-dihydro-11-oxodibenz (b, f) oxepin-2-yl) propionic acid, is a potent non-steroidal antipyretic agent. Metabolism of bermoprofen in man was studied after oral administration by gas chromatography-mass spectrometry. The results were as follows:
1. Three metabolites were identified together with the unchanged drug in human plasma, a 11-hydroxy metabolite (M 1), a 8-carboxy-11-hydroxy metabolite (M2) and a 8-carboxy metabolite (M 3).
2. In urine, the glucuronic acid conjugates of bermoprofen and M 1 were also detected together with the above metabolites.
3. The major metabolic pathway of bermoprofen in man was found to be the reduction of the carbonyl group at 11 position, followed by the conjugation with glucuronic acid, which was similar to that in monkey.

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Pharmacokinetics of bermoprofen, a new non-steroidal antipyretic agent, were evaluated in male healthy volunteers. The subjects were given single oral dose (5, 10, 20 and 40 mg, each of 5 subjects) and repeated oral dose (15 and 20 mg × 3/day for a day and 20 mg × 3/day for 5 days, each of 5 subjects). The results were as follows:
1. Mean plasma levels of the unchanged drug were maximal at 0.5-1 h and dose-related after single dosing of 5, 10, 20 and 40 mg with levels of 164, 247, 415 and 1325 ng/ml, respectively, followed by a biphasic decrease with apparent half-lives of 0.5-0.8 h (α-phase) and 1.9-2.1 h (β-phase). M 1, a 11-oxo-reduced metabolite, showed higer plasma levels and longer elimination half-lives than those of the unchanged drug. Plasma levels of M 2 and M 3 were less than 1/30 of that of the unchanged drug.
2. More than 99.5 % of bermoprofen and M 1 was bound to plasma protein.
3. A total amount excreted with urine for 48 h was 66-75 % of the dose after single dosing. The major excretion route was the glucuronidation of M 1 and bermoprofen, these conjugates being more than 80 % of the urinary excretion. The excretions of bermoprofen, M 1, M 2 and M 3 amounted to about 2-5 % of the dose.
4. There were no significant changes in the plasma concentration-time frofile and the fraction of urinary excretion between single and multiple doses, indicating that the pharmacokinetics of bermoprofen in man were not affected with its multiple administration.

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Since cannabinoids have high lipophilic properties, they could interact with biomembranes. As a result, there have been considerable hypotheses that some effects of the cannabinoids are caused by nonspecifie and specific interactions with biomembranes. This review describes the interactions of the cannabinoids with biomembranes and some enzymes (membrane integrity and fluidity, ATPase, drug metabolizing enzymes, adenylate cyclase and cannabinoid receptor) for understanding the action mechanism of the cannabinoids as model compounds of high lipophilic drugs. To understand the mechanism, it is important to distinguish nonspecific and specific interactions of the cannabinoids with biomembranes. Development of an assay system which is closely associated with psychoactivity of the cannabinoids will be also essential for understanding the mechanism.

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The multiple indicator dilution method (MID) is one experimental technique for evaluating capillary transport parameters of highly permeable neuroreceptor ligands. This technique has been widely used for the determination of capillary permeability in various organs and was adapted for studies of the blood brain barrier in rat, dog and human. Recently, Hertz and Paulson found that the apparent extraction of various substances increases during the initial part of the dilution curves in human brain. This increase in the apparent extraction can be explained by heterogeneity of transit times through the cerebral microcirculation. It is also important to consider intravascular separation of the test and reference substances (the effect of plasma protein binding and red cell carriage) and the effect of recirculation. Due to the highly tortuous character of the brain microcirculation, a distributed model of vascular transit that assumes a well-mixed tissue compartment to analyze indicator dilution curves from brain was developed. MID experiments based on the heterogeneity of capillary transit time can be used to estimate the transcapillary fluxes (both influx and efflux processes) of a highly diffusable test compound in the brain of a single animal. This appoach is potentially usefull in the study of the transport processes of lipophilic drugs and receptor-ligands that rapidly permeate brain capillaries.

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