[Influence of immunopotentiators on the activation of 5-FU derivatives]

As it has been shown that various kinds of immunopotentiators inhibit the hepatic microsomal drug-metabolizing enzymes and reduce the activation of masked compounds such as tegafur, we investigated the influence of immunopotentiators (OK-432 and PSK) on the activation of carmofur (HCFU), which is known to be transformed spontaneously in to the tumor-active substance, 5-fluorouracil (5-FU), in vivo, and compared the results to those obtained for tegafur. After oral administration of tegafur, the area under the plasma concentration curves of 5-FU in rats pretreated with OK-432 and PSK were 72% and 79% of those in untreated rats, while in the case of HCFU almost similar plasma concentration curves for 5-FU were obtained in both treated and untreated rats. These results show that the activation of HCFU to 5-FU is not influenced by treatment with these immunopotentiators. Furthermore, our clinical investigation showed that the survival curves of cancer patients given combination therapy of tegafur with OK-432 tended to be lower than those given a single therapy of tegafur, supporting the above mentioned basic results.

[Intrauterine treatment of nonimmunologic hydrops fetalis associated with pleural effusion]

Four fetuses with nonimmunologic hydrops fetalis were treated in utero. The initial diagnosis was made between 27 and 32 weeks of gestation. All fetuses had generalized edema and pleural effusion at the time of diagnosis. In order to maintain plasma colloid osmotic pressure in the fetus, fetal transfusion of albumin was carried out. Because pleural effusion may inhibit fetal lung development, serial in utero thoracocentesis guided by ultrasonic tomography was carried out. In three of four fetuses, cord blood albumin concentration were within normal range. Urine volume in fetuses significantly increased after fetal transfusion of albumin. These results suggested that this procedure was useful in maintaining plasma colloid osmotic pressure in the fetus. Although pleural effusion was removed completely by in utero thoracocentesis, pleural effusion appeared within 1 hour after the procedure and rapidly increased thereafter until the 24th hour. There were no fatal trauma from the procedure. In all infants, generalized edema, ascites and pleural effusion were presented at birth, and Apgar scores at one minute were less than 7. All died of pulmonary insufficiency within 16 hours after delivery. At autopsy, their lungs were smaller than those of the other infants.

Dose-dependent pharmacokinetics of aprindine in healthy volunteers

The disposition of aprindine following a single oral dose can best be described by a two-compartment open model. The mean plasma half-life (t 1/2 beta) increased from 8.0 +/- 2.1 h (SD) after a 25 mg dose of 9.4 +/- 2.9 h after 50 mg and to 15.8 +/- 2.6 h after 100 mg, with a decrease in total plasma clearance (Cl/F) and volume of distribution at steady state (V dss/F) and during beta-phase (V d beta/F). The area under plasma concentration-time curve (AUC), maximum plasma concentration (C max) and the amount of unchanged aprindine excreted in the urine increased in a non-linear fashion with the increase in dose. The t 1/2 beta after multiple oral doses showed a 3-fold increase over the single dose value. These results indicate that aprindine shows dose-dependent non-linear kinetics.

A new tumor-promoting agent, dihydroteleocidin B, markedly enhances chemically induced malignant cell transformation

Teleocidin, which was isolated from mycelia of Streptomyces, is a potent tumor promoter in mouse skin. The catalytically hydrogenated compound dihydroteleocidin B markedly enhanced malignant cell transformation induced by 3-methylcholanthrene or ultraviolet radiation. Dihydroteleocidin B was at least 100 times more effective in enhancing transformation than 12-O-tetradecanoyl phorbol-13-acetate, the strongest promoter known until now, whereas both promoters showed equal capacities to induce early membrane effects and DNA synthesis.

Induction of hepatocellular carcinoma in rat liver by initial treatment with benzo(a)pyrene after partial hepatectomy and promotion by phenobarbital

The hepatocarcinogenicity of benzo(a)pyrene(BP) in the rat was examined. Rats were treaated with BP after partial hepatectomy and then kept on a diet containing phenobarbital (PB) as a promoter. Tumors including a hepatocellular carcinoma developed in the rat liver by week 52.

Metabolism of benzo[A]pyrene and the related enzyme activities in hamster embryo cells

The rate of metabolism of benzo[a]pyrene (BP) and changes in related enzyme activities in cultured hamster embryo cells during successive subculture were studied. The activity of aryl hydrocarbon hydroxylase (AHH) was the highest when embryo cells were first dispersed in tissue culture flasks and decreased during subsequent passages. On the other hand, UDP-glucuronyl transferase activity increased gradually during successive subculture. Treatment of the cells with 13 nmol/ml of benz[a]anthracene (BA) for 24 h increased the activity of AHH but not that of UDP-glucuronyl transferase. The metabolism of BP was measured in cells of the passages 1, 3 and 7; metabolism of BP was most efficient in cells in passage 3 and their formation of glucuronic acid conjugates of BP, one of the major metabolites found in the medium, was 3- and 10-fold more than those of cells in passages 1 and 7, respectively. Analysis of BP-metabolites extracted from the medium with ethylacetate showed that the main metabolites were 9,10-diol and 7,8-diol. Phenols and quinones were released by treatment of the medium with beta- glucuronidase and their amounts were larger than those of diols at all passages. These results show that in hamster embryo cells in early passage, BP is metabolized to conjugates of phenols with glucuronic acid.

Metabolism of benzo[A]pyrene in hamster embryo cells. Effect of the concentration of benzo[A]pyrene on its metabolism

The metabolism of benzo[a]pyrene (BP) by hamster embryo cells was studied. The production of water-soluble metabolites, shown to be conjugates with glucuronic acid, depended on BP concentration. With increased BP concentration the amount of glucuronic acid conjugates increased, but the proportion of conjugates in BP or its metabolites present in the medium decreased. The metabolites extracted with ethylacetate were trans-7,8-dihydrodiol-BP (7,8-dihydrodiol) and trans-9,10-dihydrodiol-BP (9,10-dihydrodiol), but large peaks of phenolic metabolites were found by high pressure liquid chromatography (HPLC) after digesting the medium with beta-glucuronidase. Therefore, BP is metabolized to oxygenated forms, and of these, most of the phenolic metabolites and parts of the dihydrodiols are conjugated with glucuronic acid. The proportions of dihydrodiols to phenols, estimated by HPLC after beta-glucuronidase digestion, decreased when the BP concentration was decreased. The results suggest that dihydrodiols are less readily glucuronidated than phenols and so may be metabolized further to metabolites other than glucuronic acid conjugates.

Glucuronidation of benzo[a]pyrene in hamster embryo cells

The formation of water-soluble metabolites of tritium-labeled benzo[a]pyrene (BP) by cultured hamster embryo cells was studied. The ratio of the radioactivity in the aqueous phase to that in the organic phase increased with the incubation period. After incubation for 48 h with 3.75 nmol/ml of [3H] BP in the medium more than 90% of the 3H-radioactivity was found in the aqueous phase, whereas with 10-fold more BP about half the radioactivity remained in the organic phase. The main metabolites extracted from the medium at 37.5 nmol/ml BP with ethyl acetate by high pressure liquid chromatography (HPLC) were 9,10-diol and 7,8-diol; but after treatment of the medium with beta-glucuronidase the main oxygenated metabolites were phenols, the amount of 9-OH BP being more than that of 3-OH BP. beta-Glucuronidase also released 9,10-diol and 7,8-diol, but most of these diols were in the free form in the medium. The medium from cells treated with 3.75 nmol/ml BP has a quantitatively different profile, and most of the radioactivity obtained by extraction with organic solvent and digestion with beta-glucuronidase was eluted in the regions of phenols. These results show that in hamster embryo cells BP is mainly metabolised to conjugates of phenols with glucuronic acid.

In vitro morphological transformation of cryopreserved hamster embryo cells with tobacco tar

Cryopreserved primary cultures of Syrian golden hamster embryo cells were used as the source of target and feeder cells for in vitro bioassay of carcinogenesis. Since cultures that gave the best overall response in a preliminary test were used for the bioassay, in almost every case a range of responses was obtained. By the use of this of this bioassay system, the capacities of tobacco tar and its subfractions to induce morphological transformation were examined. Some fractions induced typical morphologically transformed colonies. A close correlation was observed between morphological transformation and bacterial mutagenesis.